explanation      blue bibcodes open ADS page with paths to full text
Author name code: vrsnak
ADS astronomy entries on 2022-09-14
author:"Vrsnak, Bojan" 

---------------------------------------------------------
Title: Determination of CME orientation and consequences for their
    propagation
Authors: Martinic, Karmen; Vrsnak, Bojan; Veronig, Astrid; Dumbovic,
   Mateja; Temmer, Manuela
2022cosp...44.2441M    Altcode:
  The configuration of the interplanetary magnetic field and features
  of the related ambient solar wind in the ecliptic and meridional
  plane are different. Therefore, one can expect that the orientation
  of the flux rope axis of a coronal mass ejection (CME) influences
  the propagation of the CME itself. However, the determination of the
  CME's orientation remains a challenging task to perform. This study
  aims to provide a reference to different CME orientation determination
  methods in the near-Sun environment. Also, it aims to investigate the
  non-radial flow in the sheath region of the interplanetary CME (ICME)
  in order to provide the first proxy to relate the ICME orientation
  with its propagation. We investigated 22 isolated CME-ICME events
  in the period 2008-2015. We first determined the CME orientation in
  the near-Sun environment using a 3D reconstruction of the CME with
  the graduated cylindrical shell (GCS) model applied to coronagraphic
  images provided by the STEREO and SOHO missions. The CME orientation
  in the near-Sun environment was determined using an ellipse fitting
  technique to the CME outer front as determined from the SOHO/LASCO
  coronagraph. In the near-Earth environment, we obtained the orientation
  of the corresponding ICME using in-situ plasma and field data and also
  investigated the non-radial flow in its sheath region. The ability of
  GCS and ellipse fitting to determine the CME orientation is found to be
  limited to reliably distinguish only between the high or low inclination
  of the events. Most of the CME-ICME pairs under investigation were
  found to be characterized by a low inclination. The majority of
  CME-ICME pairs have a consistent estimation of tilt from remote and
  in situ data. The observed non-radial flows in the sheath region show
  a greater y-direction to z-direction flow ratio for high-inclination
  events indicating that CME orientation could have an impact to the
  CME propagation.

---------------------------------------------------------
Title: Development and evaluation of Drag-Based Ensemble Model (DBEM)
Authors: Čalogović, Jaša; Vrsnak, Bojan; Veronig, Astrid; Dumbovic,
   Mateja; Temmer, Manuela
2022cosp...44.3443C    Altcode:
  The Drag-based Model (DBM) is a well-known 2D analytical model for
  simulating the heliospheric propagation of Coronal Mass Ejections
  (CMEs). Main output is the prediction of the CME arrival time and
  speed at Earth or any other given target in the solar system. Due to a
  very short computational time of DBM (< 0.01s), the probabilistic
  Drag-Based Ensemble Model (DBEM) was developed by making an ensemble
  of n different input parameters to account for possible variability
  (uncertainties) in the input parameters. Using such an approach
  to obtain the distribution and significance of the DBM results,
  the DBEM determines the CME hit chance, most probable arrival times
  and speeds, quantifies the prediction uncertainties and calculates
  the confidence intervals. As an important tool for space weather
  forecasters, the fully operational DBM/DBEM web application is
  integrated as one of the ESA Space Situational Awareness portal services
  (https://swe.ssa.esa.int/current-space-weather). In the last few years,
  DBM/DBEM has been constantly improved with various new features such as
  Graduated Cylindrical Shell (GCS) option for the CME geometry input,
  the CME propagation visualizations as well as a new DBEM version
  employing the variable solar wind speeds. The model development,
  new features and the corresponding model evaluations will be presented.

---------------------------------------------------------
Title: Galactic cosmic rays as signatures of interplanetary transients
Authors: Dumbovic, Mateja; Kühl, Patrick; Heber, Bernd; Vrsnak,
   Bojan; Temmer, Manuela; Kirin, Anamarija; Hörlöck, Malte; Jensen,
   Stefan; Benko, Ilona; Kramaric, Luka
2022cosp...44.1255D    Altcode:
  Coronal mass ejections (CMEs), interplanetary shocks, and corotating
  interaction regions (CIRs) drive heliospheric variability, causing
  various interplanetary as well as planetary disturbances. One of
  their very common in-situ signatures are short-term reductions in
  the galactic cosmic ray (GCR) flux (i.e. Forbush decreases), which
  are measured by ground-based instruments at Earth and Mars, as well
  as various spacecraft throughout the heliosphere (most recently
  by Solar Orbiter). In general, interplanetary magnetic structures
  interact with GCRs producing depressions in the GCR flux. Therefore,
  different types of interplanetary magnetic structures cause different
  types of Forbush decreases, allowing us to distinguish between
  them. We recently developed and employed two different analytical
  models to explain CME-related and CIR-related Forbush decreases,
  using an expansion-diffusion and the convection-diffusion approaches,
  respectively. We used observation-based generic CME and CIR profiles
  as the theoretical background for the models and tested the models on
  various case studies. Moreover, the CME-related Forbush decrease model
  (ForbMod, Dumbovic et al., 2018; 2020) is brought one step further, as
  it also considers the energy dependance of the detector with which the
  measurements are made. ForbMod is tested through model-to-observations
  comparison to analyse to how many CMEs it is applicable and could
  ultimately provide a helpful tool to analyse Forbush decreases. With
  new modelling efforts, as well as observational analysis we are one
  step closer in utilizing GCR measurements to provide information
  on interplanetary transients, especially where other measurements
  (e.g. plasma, magnetic field) are lacking.

---------------------------------------------------------
Title: Determination of coronal mass ejection orientation and
    consequences for their propagation
Authors: Martinić, K.; Dumbović, M.; Temmer, M.; Veronig, A.;
   Vršnak, B.
2022A&A...661A.155M    Altcode: 2022arXiv220410112M
  Context. The configuration of the interplanetary magnetic field
  and features of the related ambient solar wind in the ecliptic
  and meridional plane are different. Therefore, one can expect that
  the orientation of the flux-rope axis of a coronal mass ejection
  (CME) influences the propagation of the CME itself. However, the
  determination of the CME orientation, especially from image data,
  remains a challenging task to perform. Aim. This study aims to provide
  a reference to different CME orientation determination methods in
  the near-Sun environment. Also, it aims to investigate the non-radial
  flow in the sheath region of the interplanetary CME (ICME) in order
  to provide the first proxy to relate the ICME orientation with its
  propagation. <BR /> Methods: We investigated 22 isolated CME-ICME
  events in the period 2008-2015. We determined the CME orientation in
  the near-Sun environment using the following: (1) a 3D reconstruction
  of the CME with the graduated cylindrical shell (GCS) model applied
  to coronagraphic images provided by the STEREO and SOHO missions;
  and (2) an ellipse fitting applied to single spacecraft data from
  SOHO/LASCO C2 and C3 coronagraphs. In the near-Earth environment,
  we obtained the orientation of the corresponding ICME using in situ
  plasma and field data and also investigated the non-radial flow in
  its sheath region. <BR /> Results: The ability of GCS and ellipse
  fitting to determine the CME orientation is found to be limited to
  reliably distinguish only between the high or low inclination of the
  events. Most of the CME-ICME pairs under investigation were found to
  be characterized by a low inclination. For the majority of CME-ICME
  pairs, we obtain consistent estimations of the tilt from remote and
  in situ data. The observed non-radial flows in the sheath region show
  a greater y direction to z direction flow ratio for high-inclination
  events, indicating that the CME orientation could have an impact on
  the CME propagation.

---------------------------------------------------------
Title: How the area of solar coronal holes affects the properties
of high-speed solar wind streams near Earth: An analytical model
Authors: Hofmeister, Stefan J.; Asvestari, Eleanna; Guo, Jingnan;
   Heidrich-Meisner, Verena; Heinemann, Stephan G.; Magdalenic, Jasmina;
   Poedts, Stefaan; Samara, Evangelia; Temmer, Manuela; Vennerstrom,
   Susanne; Veronig, Astrid; Vršnak, Bojan; Wimmer-Schweingruber, Robert
2022A&A...659A.190H    Altcode: 2022arXiv220315689H
  Since the 1970s it has been empirically known that the area of
  solar coronal holes affects the properties of high-speed solar wind
  streams (HSSs) at Earth. We derive a simple analytical model for the
  propagation of HSSs from the Sun to Earth and thereby show how the
  area of coronal holes and the size of their boundary regions affect
  the HSS velocity, temperature, and density near Earth. We assume that
  velocity, temperature, and density profiles form across the HSS cross
  section close to the Sun and that these spatial profiles translate
  into corresponding temporal profiles in a given radial direction due
  to the solar rotation. These temporal distributions drive the stream
  interface to the preceding slow solar wind plasma and disperse with
  distance from the Sun. The HSS properties at 1 AU are then given by
  all HSS plasma parcels launched from the Sun that did not run into
  the stream interface at Earth distance. We show that the velocity
  plateau region of HSSs as seen at 1 AU, if apparent, originates from
  the center region of the HSS close to the Sun, whereas the velocity
  tail at 1 AU originates from the trailing boundary region. Small
  HSSs can be described to entirely consist of boundary region plasma,
  which intrinsically results in smaller peak velocities. The peak
  velocity of HSSs at Earth further depends on the longitudinal width
  of the HSS close to the Sun. The shorter the longitudinal width of
  an HSS close to the Sun, the more of its "fastest" HSS plasma parcels
  from the HSS core and trailing boundary region have impinged upon the
  stream interface with the preceding slow solar wind, and the smaller
  is the peak velocity of the HSS at Earth. As the longitudinal width
  is statistically correlated to the area of coronal holes, this also
  explains the well-known empirical relationship between coronal hole
  areas and HSS peak velocities. Further, the temperature and density
  of HSS plasma parcels at Earth depend on their radial expansion from
  the Sun to Earth. The radial expansion is determined by the velocity
  gradient across the HSS boundary region close to the Sun and gives
  the velocity-temperature and density-temperature relationships at
  Earth their specific shape. When considering a large number of HSSs,
  the assumed correlation between the HSS velocities and temperatures
  close to the Sun degrades only slightly up to 1 AU, but the correlation
  between the velocities and densities is strongly disrupted up to 1
  AU due to the radial expansion. Finally, we show how the number of
  particles of the piled-up slow solar wind in the stream interaction
  region depends on the velocities and densities of the HSS and preceding
  slow solar wind plasma.

---------------------------------------------------------
Title: Generic profile of a long-lived corotating interaction region
    and associated recurrent Forbush decrease
Authors: Dumbović, M.; Vršnak, B.; Temmer, M.; Heber, B.; Kühl, P.
2022A&A...658A.187D    Altcode: 2022arXiv220109623D
  Context. Corotating interaction regions (CIRs), formed by the
  interaction of slow solar wind and fast streams that originate from
  coronal holes (CHs), produce recurrent Forbush decreases, which are
  short-term depressions in the galactic cosmic ray (GCR) flux. <BR />
  Aims: Our aim is to prepare a reliable set of CIR measurements to be
  used as a textbook for modeling efforts. For that purpose, we observe
  and analyse a long-lived CIR, originating from a single CH, recurring
  in 27 consecutive Carrington rotations 2057-2083 in the time period
  from June 2007-May 2009. <BR /> Methods: We studied the in situ
  measurements of this long-lived CIR as well as the corresponding
  depression in the cosmic ray (CR) count observed by SOHO/EPHIN
  throughout different rotations. We performed a statistical analysis,
  as well as the superposed epoch analysis, using relative values of the
  key parameters: the total magnetic field strength, B, the magnetic
  field fluctuations, dBrms, plasma flow speed, v, plasma density, n,
  plasma temperature, T, and the SOHO/EPHIN F-detector particle count,
  and CR count. <BR /> Results: We find that the mirrored CR count-time
  profile is correlated with that of the flow speed, ranging from moderate
  to strong correlation, depending on the rotation. In addition, we
  find that the CR count dip amplitude is correlated to the peak in the
  magnetic field and flow speed of the CIR. These results are in agreement
  with previous statistical studies. Finally, using the superposed epoch
  analysis, we obtain a generic CIR example, which reflects the in situ
  properties of a typical CIR well. <BR /> Conclusions: Our results are
  better explained based on the combined convection-diffusion approach of
  the CIR-related GCR modulation. Furthermore, qualitatively, our results
  do not differ from those based on different CHs samples. This indicates
  that the change of the physical properties of the recurring CIR from one
  rotation to another is not qualitatively different from the change of
  the physical properties of CIRs originating from different CHs. Finally,
  the obtained generic CIR example, analyzed on the basis of superposed
  epoch analysis, can be used as a reference for testing future models.

---------------------------------------------------------
Title: Analytic modeling of recurrent Forbush decreases caused by
    corotating interaction regions
Authors: Vršnak, B.; Dumbović, M.; Heber, B.; Kirin, A.
2022A&A...658A.186V    Altcode: 2022arXiv220109619V
  Context. On scales of days, the galactic cosmic ray (GCR) flux is
  affected by coronal mass ejections and corotating interaction regions
  (CIRs), causing so-called Forbush decreases and recurrent Forbush
  decreases (RFDs), respectively. <BR /> Aims: We explain the properties
  and behavior of RFDs recorded at about 1 au that are caused by CIRs
  generated by solar wind high-speed streams (HSSs) that emanate from
  coronal holes. <BR /> Methods: We employed a convection-diffusion GCR
  propagation model based on the Fokker-Planck equation and applied it to
  solar wind and interplanetary magnetic field properties at 1 au. <BR />
  Results: Our analysis shows that the only two effects that are relevant
  for a plausible overall explanation of the observations are the enhanced
  convection effect caused by the increased velocity of the HSS and the
  reduced diffusion effect caused by the enhanced magnetic field and its
  fluctuations within the CIR and HSS structure. These two effects that
  we considered in the model are sufficient to explain not only the main
  signatures of RFDs, but also the sometimes observed "over-recovery"
  and secondary dips in RFD profiles. The explanation in terms of the
  convection-diffusion GCR propagation hypothesis is tested by applying
  our model to the observations of a long-lived CIR that recurred over 27
  rotations in 2007-2008. <BR /> Conclusions: Our analysis demonstrates
  a very good match of the model results and observations.

---------------------------------------------------------
Title: Influence of the CME Orientation on the ICME Propagation
Authors: Martinic, Karmen; Dumbovic, Mateja; Vrsnak, Bojan
2021AGUFMSH35B2057M    Altcode:
  Beyond certain distance the ICME propagation becomes mostly governed by
  the interaction of the ICME and the ambient solar wind. Configuration
  of the interplanetary magnetic field and features of the related
  ambient solar wind in the ecliptic and meridional plane are
  different. Therefore, one can expect that the inclination of the
  CME flux rope axis i.e. tilt, influences the propagation of the ICME
  itself. In order to study the relation between the tilt parameter and
  the ICME propagation we investigated isolated Earth-impacting CME-ICME
  evets in the time period from 2006. to 2014. We determined the CME
  tilt in the near-Sun environment from the 3D reconstruction of the CME,
  obtained by the Graduated Cylindrical Shell model using coronagraphic
  images provided by the STEREO and SOHO missions. We determined the
  tilt of the ICME in the near-Earth environment using in-situ data. We
  constrained our study to CME-ICME events that show no evidence of
  rotation while propagating, i.e. have a similar tilt in the near-Sun
  and near-Earth environment. For those events we also calculated the drag
  parameter to check the implications for space-weather forecasting using
  the drag based(ensemble) [DB(E)M] model of heliospheric propagation.

---------------------------------------------------------
Title: Earth-affecting solar transients: a review of progresses in
    solar cycle 24
Authors: Zhang, Jie; Temmer, Manuela; Gopalswamy, Nat; Malandraki,
   Olga; Nitta, Nariaki V.; Patsourakos, Spiros; Shen, Fang; Vršnak,
   Bojan; Wang, Yuming; Webb, David; Desai, Mihir I.; Dissauer, Karin;
   Dresing, Nina; Dumbović, Mateja; Feng, Xueshang; Heinemann, Stephan
   G.; Laurenza, Monica; Lugaz, Noé; Zhuang, Bin
2021PEPS....8...56Z    Altcode: 2020arXiv201206116Z
  This review article summarizes the advancement in the studies of
  Earth-affecting solar transients in the last decade that encompasses
  most of solar cycle 24. It is a part of the effort of the International
  Study of Earth-affecting Solar Transients (ISEST) project, sponsored
  by the SCOSTEP/VarSITI program (2014-2018). The Sun-Earth is an
  integrated physical system in which the space environment of the
  Earth sustains continuous influence from mass, magnetic field, and
  radiation energy output of the Sun in varying timescales from minutes to
  millennium. This article addresses short timescale events, from minutes
  to days that directly cause transient disturbances in the Earth's
  space environment and generate intense adverse effects on advanced
  technological systems of human society. Such transient events largely
  fall into the following four types: (1) solar flares, (2) coronal mass
  ejections (CMEs) including their interplanetary counterparts ICMEs,
  (3) solar energetic particle (SEP) events, and (4) stream interaction
  regions (SIRs) including corotating interaction regions (CIRs). In
  the last decade, the unprecedented multi-viewpoint observations of
  the Sun from space, enabled by STEREO Ahead/Behind spacecraft in
  combination with a suite of observatories along the Sun-Earth lines,
  have provided much more accurate and global measurements of the size,
  speed, propagation direction, and morphology of CMEs in both 3D and over
  a large volume in the heliosphere. Many CMEs, fast ones, in particular,
  can be clearly characterized as a two-front (shock front plus ejecta
  front) and three-part (bright ejecta front, dark cavity, and bright
  core) structure. Drag-based kinematic models of CMEs are developed to
  interpret CME propagation in the heliosphere and are applied to predict
  their arrival times at 1 AU in an efficient manner. Several advanced
  MHD models have been developed to simulate realistic CME events from
  the initiation on the Sun until their arrival at 1 AU. Much progress
  has been made on detailed kinematic and dynamic behaviors of CMEs,
  including non-radial motion, rotation and deformation of CMEs, CME-CME
  interaction, and stealth CMEs and problematic ICMEs. The knowledge
  about SEPs has also been significantly improved. An outlook of how to
  address critical issues related to Earth-affecting solar transients
  concludes this article.

---------------------------------------------------------
Title: Coronal Hole Detection and Open Magnetic Flux
Authors: Linker, Jon A.; Heinemann, Stephan G.; Temmer, Manuela;
   Owens, Mathew J.; Caplan, Ronald M.; Arge, Charles N.; Asvestari,
   Eleanna; Delouille, Veronique; Downs, Cooper; Hofmeister, Stefan J.;
   Jebaraj, Immanuel C.; Madjarska, Maria S.; Pinto, Rui F.; Pomoell,
   Jens; Samara, Evangelia; Scolini, Camilla; Vršnak, Bojan
2021ApJ...918...21L    Altcode: 2021arXiv210305837L
  Many scientists use coronal hole (CH) detections to infer open
  magnetic flux. Detection techniques differ in the areas that they
  assign as open, and may obtain different values for the open magnetic
  flux. We characterize the uncertainties of these methods, by applying
  six different detection methods to deduce the area and open flux of
  a near-disk center CH observed on 2010 September 19, and applying
  a single method to five different EUV filtergrams for this CH. Open
  flux was calculated using five different magnetic maps. The standard
  deviation (interpreted as the uncertainty) in the open flux estimate
  for this CH ≍ 26%. However, including the variability of different
  magnetic data sources, this uncertainty almost doubles to 45%. We
  use two of the methods to characterize the area and open flux for
  all CHs in this time period. We find that the open flux is greatly
  underestimated compared to values inferred from in situ measurements
  (by 2.2-4 times). We also test our detection techniques on simulated
  emission images from a thermodynamic MHD model of the solar corona. We
  find that the methods overestimate the area and open flux in the
  simulated CH, but the average error in the flux is only about 7%. The
  full-Sun detections on the simulated corona underestimate the model
  open flux, but by factors well below what is needed to account for
  the missing flux in the observations. Under-detection of open flux in
  coronal holes likely contributes to the recognized deficit in solar
  open flux, but is unlikely to resolve it.

---------------------------------------------------------
Title: Probabilistic Drag-Based Ensemble Model (DBEM) Evaluation
    for Heliospheric Propagation of CMEs
Authors: Čalogović, Jaša; Dumbović, Mateja; Sudar, Davor; Vršnak,
   Bojan; Martinić, Karmen; Temmer, Manuela; Veronig, Astrid M.
2021SoPh..296..114C    Altcode: 2021arXiv210706684C
  The Drag-based Model (DBM) is a 2D analytical model for heliospheric
  propagation of Coronal Mass Ejections (CMEs) in ecliptic plane
  predicting the CME arrival time and speed at Earth or any other given
  target in the solar system. It is based on the equation of motion and
  depends on initial CME parameters, background solar wind speed, w and
  the drag parameter γ . A very short computational time of DBM (&lt;
  0.01 s) allowed us to develop the Drag-Based Ensemble Model (DBEM)
  that takes into account the variability of model input parameters
  by making an ensemble of n different input parameters to calculate
  the distribution and significance of the DBM results. Thus the DBEM
  is able to calculate the most likely CME arrival times and speeds,
  quantify the prediction uncertainties and determine the confidence
  intervals. A new DBEMv3 version is described in detail and evaluated
  for the first time determining the DBEMv3 performance and errors by
  using various CME-ICME lists and it is compared with previous DBEM
  versions, ICME being a short-hand for interplanetary CME. The analysis
  to find the optimal drag parameter γ and ambient solar wind speed
  w showed that somewhat higher values (γ ≈0.3 ×10<SUP>−7</SUP>
  km<SUP>−1</SUP>, w ≈ 425 km s<SUP>−1</SUP>) for both of these DBEM
  input parameters should be used for the evaluation than the previously
  employed ones. Based on the evaluation performed for 146 CME-ICME pairs,
  the DBEMv3 performance with mean error (ME) of −11.3 h, mean absolute
  error (MAE) of 17.3 h was obtained. There is a clear bias towards
  the negative prediction errors where the fast CMEs are predicted to
  arrive too early, probably due to the model physical limitations and
  input errors (e.g. CME launch speed). This can be partially reduced by
  using larger values for γ resulting in smaller prediction errors (ME
  =−3.9 h, MAE = 14.5 h) but at the cost of larger prediction errors
  for single fast CMEs as well as larger CME arrival speed prediction
  errors. DBEMv3 showed also slight improvement in the performance for
  all calculated output parameters compared to the previous DBEM versions.

---------------------------------------------------------
Title: Drag-based model (DBM) tools for forecast of coronal mass
    ejection arrival time and speed
Authors: Dumbović, Mateja; Čalogović, Jaša; Martinić, Karmen;
   Vršnak, Bojan; Sudar, Davor; Temmer, Manuela; Veronig, Astrid
2021FrASS...8...58D    Altcode: 2021arXiv210314292D
  Forecasting the arrival time of coronal mass ejections (CMEs) and
  their associated shocks is one of the key aspects of space weather
  research and predictions. One of the commonly used models is, due
  to its simplicity and calculation speed, the analytical drag-based
  model (DBM) for heliospheric propagation of CMEs. DBM relies on
  the observational fact that slow CMEs accelerate whereas fast CMEs
  decelerate, and is based on the concept of MHD drag, which acts to
  adjust the CME speed to the ambient solar wind. Although physically
  DBM is applicable only to the CME magnetic structure, it is often used
  as a proxy for the shock arrival. In recent years, the DBM equation
  has been used in many studies to describe the propagation of CMEs
  and shocks with different geometries and assumptions. Here we give
  an overview of the five DBM versions currently available and their
  respective tools, developed at Hvar Observatory and frequently used
  by researchers and forecasters. These include: 1) basic 1D DBM, a 1D
  model describing the propagation of a single point (i.e. the apex of
  the CME) or concentric arc (where all points propagate identically); 2)
  advanced 2D self-similar cone DBM, a 2D model which combines basic DBM
  and cone geometry describing the propagation of the CME leading edge
  which evolves self-similarly; 3) 2D flattening cone DBM, a 2D model
  which combines basic DBM and cone geometry describing the propagation
  of the CME leading edge which does not evolve self-similarly; 4)
  DBEMv1, an ensemble version of the 2D flattening cone DBM which uses
  CME ensembles as an input and 5) DBEMv3, an ensemble version of the
  2D flattening cone DBM which creates CME ensembles based on the input
  uncertainties. All five versions have been tested and published in
  recent years and are available online or upon request. We provide an
  overview of these five tools, of their similarities and differences,
  as well as discuss and demonstrate their application.

---------------------------------------------------------
Title: Influence of the CME orientation on the ICME propagation
Authors: Martinić, Karmen; Dumbović, Mateja; Vršnak, Bojan
2021EGUGA..23.2526M    Altcode:
  Beyond certain distance the ICME propagation becomes mostly governed by
  the interaction of the ICME and the ambient solar wind. Configuration
  of the interplanetary magnetic field and features of the related
  ambient solar wind in the ecliptic and meridional plane are
  different. Therefore, one can expect that the inclination of the
  CME flux rope axis i.e. tilt, influences the propagation of the ICME
  itself. In order to study the relation between the tilt parameter and
  the ICME propagation we investigated isolated Earth-impacting CME-ICME
  evets in the time period from 2006. to 2014. We determined the CME tilt
  in the "near-Sun" environment from the 3D reconstruction of the CME,
  obtained by the Graduated Cylindrical Shell model using coronagraphic
  images provided by the STEREO and SOHO missions. We determined the tilt
  of the ICME in the "near-Earth" environment using in-situ data. We
  constrained our study to CME-ICME events that show no evidence of
  rotation while propagating, i.e. have a similar tilt in the "near-Sun"
  and "near-Earth" environment. We present preliminary results of our
  study and discuss their implications for space-weather forecasting using
  the drag-based(ensemble) [DB(E)M] model of heliospheric propagation.

---------------------------------------------------------
Title: Deriving CME volume and density from remote sensing data
Authors: Temmer, Manuela; Holzknecht, Lukas; Dumbovic, Mateja;
   Vrsnak, Bojan; Sachdeva, Nishtha; Heinemann, Stephan G.; Dissauer,
   Karin; Scolini, Camilla; Asvestari, Eleanna; Veronig, Astrid M.;
   Hofmeister, Stefan
2021EGUGA..23.2535T    Altcode:
  Using combined STEREO-SOHO white-light data, we present a method to
  determine the volume and density of a coronal mass ejection (CME) by
  applying the graduated cylindrical shell model (GCS) and deprojected
  mass derivation. Under the assumption that the CME mass is roughly
  equally distributed within a specific volume, we expand the CME
  self-similarly and calculate the CME density for distances close to the
  Sun (15-30 Rs) and at 1 AU. The procedure is applied on a sample of 29
  well-observed CMEs and compared to their interplanetary counterparts
  (ICMEs). Specific trends are derived comparing calculated and in-situ
  measured proton densities at 1 AU, though large uncertainties are
  revealed due to the unknown mass and geometry evolution: i) a moderate
  correlation for the magnetic structure having a mass that stays
  rather constant and ii) a weak correlation for the sheath density by
  assuming the sheath region is an extra mass - as expected for a mass
  pile-up process - that is in its amount comparable to the initial
  CME deprojected mass. High correlations are derived between in-situ
  measured sheath density and the solar wind density and solar wind speed
  as measured 24 hours ahead of the arrival of the disturbance. This
  gives additional confirmation that the sheath-plasma indeed stems from
  piled-up solar wind material. While the CME interplanetary propagation
  speed is not related to the sheath density, the size of the CME may
  play some role in how much material is piled up.

---------------------------------------------------------
Title: Validation of Global EUV Wave MHD Simulations and Observational
    Techniques
Authors: Downs, Cooper; Warmuth, Alexander; Long, David M.; Bloomfield,
   D. Shaun; Kwon, Ryun-Young; Veronig, Astrid M.; Vourlidas, Angelos;
   Vršnak, Bojan
2021ApJ...911..118D    Altcode:
  Global EUV waves remain a controversial phenomenon more than 20 yr
  after their discovery by SOHO/EIT. Although consensus is growing in the
  community that they are most likely large-amplitude waves or shocks,
  the wide variety of observations and techniques used to identify
  and analyze them have led to disagreements regarding their physical
  properties and interpretation. Here, we use a 3D magnetohydrodynamic
  (MHD) model of the solar corona to simulate an EUV wave event on 2009
  February 13 to enable a detailed validation of the various commonly used
  detection and analysis techniques of global EUV waves. The simulated
  event exhibits comparable behavior to that of a real EUV wave event,
  with similar kinematic behavior and plasma parameter evolution. The
  kinematics of the wave are estimated via visual identification and
  profile analysis, with both approaches providing comparable results. We
  find that projection effects can affect the derived kinematics of the
  wave, due to the variation in fast-mode wave speed with height in the
  corona. Coronal seismology techniques typically used for estimates
  of the coronal magnetic field are also tested and found to estimate
  fast-mode speeds comparable to those of the model. Plasma density
  and temperature variations of the wave front are also derived using
  a regularized inversion approach and found to be consistent with
  observed wave events. These results indicate that global waves are
  best interpreted as large-amplitude waves and that they can be used
  to probe the coronal medium using well-defined analysis techniques.

---------------------------------------------------------
Title: Analytical and empirical modelling of the origin and
    heliospheric propagation of coronal mass ejections, and space
    weather applications
Authors: Vršnak, Bojan
2021JSWSC..11...34V    Altcode:
  The focus is on the physical background and comprehension of the
  origin and the heliospheric propagation of interplanetary coronal
  mass ejections (ICMEs), which can cause most severe geomagnetic
  disturbances. The paper considers mainly the analytical modelling,
  providing useful insight into the nature of ICMEs, complementary
  to that provided by numerical MHD models. It is concentrated on
  physical processes related to the origin of CMEs at the Sun, their
  heliospheric propagation, up to the effects causing geomagnetic
  perturbations. Finally, several analytical and statistical forecasting
  tools for space weather applications are described.

---------------------------------------------------------
Title: Deriving CME Density From Remote Sensing Data and Comparison
    to In Situ Measurements
Authors: Temmer, M.; Holzknecht, L.; Dumbović, M.; Vršnak, B.;
   Sachdeva, N.; Heinemann, S. G.; Dissauer, K.; Scolini, C.; Asvestari,
   E.; Veronig, A. M.; Hofmeister, S. J.
2021JGRA..12628380T    Altcode: 2020arXiv201106880T
  We determine the three dimensional geometry and deprojected mass of 29
  well observed coronal mass ejections (CMEs) and their interplanetary
  counterparts (ICMEs) using combined Solar Terrestrial Relations
  Observatory Solar and Heliospheric Observatory white light data. From
  the geometry parameters, we calculate the volume of the CME for the
  magnetic ejecta (flux rope type geometry) and sheath structure (shell
  like geometry resembling the (I)CME frontal rim). Working under the
  assumption that the CME mass is roughly equally distributed within a
  specific volume, we expand the CME self similarly and calculate the CME
  density for distances close to the Sun (15-30 Rs) and at 1 AU. Specific
  trends are derived comparing calculated and in situ measured proton
  densities at 1 AU, though large uncertainties are revealed due to the
  unknown mass and geometry evolution: (1) a moderate correlation for
  the magnetic structure having a mass that stays rather constant (cc
  ≈ 0.56 - 0.59), and (2) a weak correlation for the sheath density (cc
  ≈ 0.26) by assuming the sheath region is an extra mass—as expected
  for a mass pile up process—that is in its amount comparable to the
  initial CME deprojected mass. High correlations are derived between in
  situ measured sheath density and the solar wind density (cc ≈ -0.73)
  and solar wind speed (cc ≈ 0.56) as measured 24 h ahead of the arrival
  of the disturbance. This gives additional confirmation that the sheath
  plasma indeed stems from piled up solar wind material. While the CME
  interplanetary propagation speed is not related to the sheath density,
  the size of the CME may play some role in how much material could be
  piled up.

---------------------------------------------------------
Title: Forecasting the arrival time of coronal mass ejections
Authors: Dumbovic, Mateja; Mays, M. Leila; Riley, Pete; Mierla,
   Marilena; Kay, Christina; Vrsnak, Bojan; Veronig, Astrid; Cremades,
   Hebe; Čalogović, Jaša; Verbeke, Christine; Temmer, Manuela; Sudar,
   Davor; Scolini, Camilla; Hinterreiter, Jürgen; Paouris, Evangelos;
   Palmerio, Erika; Balmaceda, Laura
2021cosp...43E1038D    Altcode:
  Forecasting the arrival time of coronal mass ejections (CMEs) and their
  associated shocks is one of the key aspects of space weather. In recent
  years many models have been developed by various research groups aiming
  to forecast CME arrival time. The models differ based on the input,
  approach, assumptions and complexity ranging from simple empirical and
  analytical to complex numerical and machine learning models. One of the
  commonly used models is, due to its simplicity and calculation speed,
  the analytical drag-based (ensemble) model [DB(E)M] for heliospheric
  propagation of CMEs. DB(E)M relies on the observational fact that
  slow CMEs accelerate whereas fast CMEs decelerate, and is based on
  the concept of MHD drag, which acts to adjust the CME speed to the
  ambient solar wind. However, regardless of the model, forecasting CME
  arrival time has proven to be exceedingly challenging. One of the major
  setbacks is the uncertainty of the CME observational input, which
  is still substantial despite state-of-the-art remote observational
  capacities such as high-resolution EUV imagers and stereoscopic
  observations. Another major setback is the uncertainty in the CME
  propagation itself, due to e.g. unrealistic background solar wind
  and/or complex interactions. These limits will be discussed in the
  scope of DB(E)M and the CME input analysis performed by the ISSI Bern
  team on the "Understanding Our Capabilities In Observing And Modeling
  Coronal Mass Ejections".

---------------------------------------------------------
Title: CME evolution and the corresponding Forbush decrease: modelling
    vs multi-spacecraft observation
Authors: Dumbovic, Mateja; Moestl, Christian; Podladchikova, Tatiana;
   Guo, Jingnan; Heber, Bernd; Vrsnak, Bojan; Dissauer, Karin; Veronig,
   Astrid; Amerstorfer, Tanja; Temmer, Manuela; Carcaboso, Fernando;
   Kirin, Anamarija
2021cosp...43E1747D    Altcode:
  One of the very common in-situ signatures of interplanetary coronal
  mass ejections (ICMEs), as well as other interplanetary transients are
  Forbush decreases (FDs), i.e. short-term reductions in the galactic
  cosmic ray (GCR) flux. FD phenomena are caused by the interaction
  of GCRs with a magnetic structure, therefore it is expected that
  different types of interplanetary substructures cause different types
  of GCR time profiles, allowing us to distinguish between shock/sheath,
  flux rope and SIR-type of FDs. Moreover, since the interaction of
  GCRs and CME magnetic structure (i.e. flux rope) occurs all the
  way from Sun to Earth, FDs reflect the evolutionary properties of
  CMEs. We apply modelling to different ICME regions in order to obtain
  a generic FD profile. We model the shock/sheath-related FD using the
  propagating diffusive barrier (PDB) model, the flux-rope-related FD
  using the diffusion model for the expanding flux rope (ForbMod),
  and the exponential time profile approximates the recovery after
  the event. The modeled generic FD profile qualitatively agrees with
  our current observation-based understanding of FDs. In addition, we
  test ForbMod against a set of multi-spacecraft observations of the
  same ICME. We find a reasonable agreement of the ForbMod model with
  multi-spacecraft measurements, indicating that modelled FDs reflect
  well the flux rope evolution.

---------------------------------------------------------
Title: Evolution of coronal mass ejections and the corresponding
Forbush decreases: modelling vs. multi-spacecraft observations
Authors: Dumbovic, M.; Vrsnak, B.; Guo, J.; Heber, B.; Dissauer, K.;
   Carcaboso-Morales, F.; Temmer, M.; Veronig, A.; Podladchikova, T.;
   Moestl, C.; Amerstorfer, T.; Kirin, A.
2020AGUFMSH046..08D    Altcode:
  One of the very common in situ signatures of interplanetary coronal
  mass ejections (ICMEs), as well as other interplanetary transients,
  are Forbush decreases (FDs), i.e. short-term reductions in the galactic
  cosmic ray (GCR) flux. A two-step FD is often regarded as a textbook
  example, which presumably owes its specific morphology to the fact that
  the measuring instrument passed through the ICME head-on, encountering
  first the shock front (if developed), then the sheath and finally the
  CME magnetic structure. The interaction of GCRs and the shock/sheath
  region, as well as the CME magnetic structure, occurs all the way from
  Sun to Earth, therefore, FDs are expected to reflect the evolutionary
  properties of CMEs and their sheaths. We apply modelling to different
  ICME regions in order to obtain a generic two-step FD profile, which
  qualitatively agrees with our current observation-based understanding of
  FDs. We next adapt the models for energy dependence to enable comparison
  with different GCR measurement instruments (as they measure in different
  particle energy ranges). We test these modelling efforts against a
  set of multi-spacecraft observations of the same event, using the
  Forbush decrease model for the expanding flux rope (ForbMod). We find
  a reasonable agreement of the ForbMod model for the GCR depression
  in the CME magnetic structure with multi-spacecraft measurements,
  indicating that modelled FDs reflect well the CME evolution.

---------------------------------------------------------
Title: Characteristics of a long-lived CIR and the corresponding
    depression in the GCR flux
Authors: Dumbovic, M.; Vrsnak, B.; Temmer, M.; Heber, B.
2020AGUFMSH0440026D    Altcode:
  We observe a long-lived CIR recurring in 27 consecutive Carrington
  rotations 2057-2083 in the time period from June 2007 - May 2009. We
  characterize the in situ measurements of this long-lived CIR as well as
  the corresponding depression in the GCR count observed by SOHO/EPHIN,
  and analyze them throughout different rotations. We find that the
  behavior of the flow speed peak roughly shows a rising phase and
  a declining phase. This is similar to the evolutionary profile of
  some observed coronal hole areas, but without a clear peak. The GCR
  count evolutionary profile roughly follows that of the flow speed
  peak, but moreover we find that the inverted GCR count time-profile
  matches very well with that of the flow speed throughout different
  rotations. We perform a statistical analysis and find the GCR count
  amplitude correlated to the peak in the magnetic field and flow
  speed, as expected based on previous statistical studies. In order
  to characterize a generic CIR profile for modelling purposes, we
  perform the superposed epoch analysis using relative values of the
  key parameters. Based on the observed properties we propose a simple
  analytical model starting from the basic Fokker-Planck equation.

---------------------------------------------------------
Title: Solar Flare-CME Coupling throughout Two Acceleration Phases
    of a Fast CME
Authors: Gou, Tingyu; Veronig, Astrid M.; Liu, Rui; Zhuang, Bin;
   Dumbović, Mateja; Podladchikova, Tatiana; Reid, Hamish A. S.; Temmer,
   Manuela; Dissauer, Karin; Vršnak, Bojan; Wang, Yuming
2020ApJ...897L..36G    Altcode: 2020arXiv200611707G
  Solar flares and coronal mass ejections (CMEs) are closely coupled
  through magnetic reconnection. CMEs are usually accelerated impulsively
  within the low solar corona, synchronized with the impulsive flare
  energy release. We investigate the dynamic evolution of a fast CME and
  its associated X2.8 flare occurring on 2013 May 13. The CME experiences
  two distinct phases of enhanced acceleration, an impulsive one with a
  peak value of ∼5 km s<SUP>-2</SUP>, followed by an extended phase with
  accelerations up to 0.7 km s<SUP>-2</SUP>. The two-phase CME dynamics
  is associated with a two-episode flare energy release. While the first
  episode is consistent with the "standard" eruption of a magnetic flux
  rope, the second episode of flare energy release is initiated by the
  reconnection of a large-scale loop in the aftermath of the eruption
  and produces stronger nonthermal emission up to γ-rays. In addition,
  this long-duration flare reveals clear signs of ongoing magnetic
  reconnection during the decay phase, evidenced by extended hard X-ray
  bursts with energies up to 100-300 keV and intermittent downflows
  of reconnected loops for &gt;4 hr. The observations reveal that the
  two-step flare reconnection substantially contributes to the two-phase
  CME acceleration, and the impulsive CME acceleration precedes the most
  intense flare energy release. The implications of this non-standard
  flare/CME observation are discussed.

---------------------------------------------------------
Title: Evolution of Coronal Mass Ejections and the Corresponding
Forbush Decreases: Modeling vs. Multi-Spacecraft Observations
Authors: Dumbović, Mateja; Vršnak, Bojan; Guo, Jingnan; Heber,
   Bernd; Dissauer, Karin; Carcaboso, Fernando; Temmer, Manuela; Veronig,
   Astrid; Podladchikova, Tatiana; Möstl, Christian; Amerstorfer, Tanja;
   Kirin, Anamarija
2020SoPh..295..104D    Altcode: 2020arXiv200602253D
  One of the very common in situ signatures of interplanetary coronal
  mass ejections (ICMEs), as well as other interplanetary transients,
  are Forbush decreases (FDs), i.e. short-term reductions in the galactic
  cosmic ray (GCR) flux. A two-step FD is often regarded as a textbook
  example, which presumably owes its specific morphology to the fact that
  the measuring instrument passed through the ICME head on, encountering
  first the shock front (if developed), then the sheath, and finally the
  CME magnetic structure. The interaction of GCRs and the shock/sheath
  region, as well as the CME magnetic structure, occurs all the way from
  Sun to Earth, therefore, FDs are expected to reflect the evolutionary
  properties of CMEs and their sheaths. We apply modeling to different
  ICME regions in order to obtain a generic two-step FD profile, which
  qualitatively agrees with our current observation-based understanding
  of FDs. We next adapt the models for energy dependence to enable
  comparison with different GCR measurement instruments (as they measure
  in different particle energy ranges). We test these modeling efforts
  against a set of multi-spacecraft observations of the same event, using
  the Forbush decrease model for the expanding flux rope (ForbMod). We
  find a reasonable agreement of the ForbMod model for the GCR depression
  in the CME magnetic structure with multi-spacecraft measurements,
  indicating that modeled FDs reflect well the CME evolution.

---------------------------------------------------------
Title: Sun-to-Earth Observations and Characteristics of Isolated
    Earth-Impacting Interplanetary Coronal Mass Ejections During 2008
    - 2014
Authors: Maričić, D.; Vršnak, B.; Veronig, A. M.; Dumbović, M.;
   Šterc, F.; Roša, D.; Karlica, M.; Hržina, D.; Romštajn, I.
2020SoPh..295...91M    Altcode: 2020arXiv200810265M
  A sample of isolated Earth-impacting interplanetary coronal mass
  ejections (ICMEs) that occurred in the period January 2008 to August
  2014 is analyzed to study in detail the ICME in situ signatures, with
  respect to the type of filament eruption related to the corresponding
  CME. Observations from different vantage points provided by the
  Solar and Heliospheric Observatory (SOHO) and the Solar Terrestrial
  Relations Observatory Ahead and Behind (STEREO-A and B) are used to
  determine whether each CME under study is Earth directed or not. For
  Earth-directed CMEs, a kinematical study was performed using the
  STEREO-A and B COR1 and COR2 coronagraphs and the Heliospheric Imagers
  (HI1), to estimate the CME arrival time at 1 AU and to link the CMEs
  with the corresponding in situ solar wind counterparts. Based on the
  extrapolated CME kinematics, we identified interacting CMEs, which
  were excluded from further analysis. Applying this approach, a set
  of 31 isolated Earth-impacting CMEs was unambiguously identified and
  related to the in situ measurements recorded by the Wind spacecraft. We
  classified the events into subsets with respect to the CME source
  location, as well as with respect to the type of the associated filament
  eruption. Hence, the events are divided into three subsamples: active
  region (AR) CMEs, disappearing filament (DSF) CMEs, and stealthy
  CMEs. The related three groups of ICMEs were further divided into
  two subsets: magnetic obstacle (MO) events (out of which four were
  stealthy), covering ICMEs that at least partly showed characteristics of
  flux ropes, and ejecta (EJ) events, not showing such characteristics. In
  this way, 14 MO-ICMEs and 17 EJ-ICMES were identified. The solar
  source regions of the non-stealthy MO-ICMEs are found to be located
  predominantly (9/10, 90%) within ±30<SUP>∘</SUP> from the solar
  central meridian, whereas EJ-ICMEs originate predominantly (16/17, 94%)
  from source regions that are outside ±30<SUP>∘</SUP>. In the next
  step, MO-events were analyzed in more detail, considering the magnetic
  field strength and the plasma characteristics in three different
  segments, defined as the turbulent sheath (TS), the frontal region
  (FR), and the MO itself. The analysis revealed various well-defined
  correlations for AR, DSF, and stealthy ICMEs, which we interpreted
  considering basic physical concepts. Our results support the hypothesis
  that ICMEs show different signatures depending on the in situ spacecraft
  trajectory, in terms of apex versus flank hits.

---------------------------------------------------------
Title: CME evolution and the corresponding Forbush decrease: modelling
    vs multi-spacecraft observation
Authors: Dumbovic, Mateja; Vrsnak, Bojan; Guo, Jingnan; Heber, Bernd;
   Dissauer, Karin; Carcaboso-Morales, Fernando; Temmer, Manuela; Veronig,
   Astrid; Podladchikova, Tatiana; Möstl, Christian; Amerstorfer, Tanja;
   Kirin, Anamarija
2020EGUGA..2210446D    Altcode:
  One of the very common in-situ signatures of ICMEs, as well as other
  interplanetary transients are Forbush decreases (FDs), i.e. short-term
  reductions in the galactic cosmic ray (GCR) flux. A two-step FD is
  often regarded as a textbook example, which presumably owns its specific
  morphology to the fact that the measuring instrument passed through the
  ICME head-on, encountering first the shock front (if developed), then
  the sheath and finally the magnetic structure. The interaction of GCRs
  and the shock/sheath region as well as CME magnetic structure occurs all
  the way from Sun to Earth, therefore, FDs are expected to reflect the
  evolutionary properties of CMEs and their sheaths. We apply modelling
  to different ICME regions in order to obtain a generic two-step FD
  profile, which qualitatively agrees with our current observation-based
  understanding of FDs. We next adapt the models for energy dependence
  to enable comparison with different GCR measurement instruments
  (as they measure in different particle energy ranges). We test these
  modelling efforts against a set of multi-spacecraft observations of
  the same event.

---------------------------------------------------------
Title: Relating CME density derived from remote sensing data to CME
    sheath solar wind plasma pile up as measured in-situ
Authors: Temmer, Manuela; Holzknecht, Lukas; Dumbovic, Mateja; Vrsnak,
   Bojan; Sachdeva, Nishtha; Heinemann, Stephan; Dissauer, Karin; Scolini,
   Camilla; Asvestari, Eleanna; Veronig, Astrid; Hofmeister, Stefan
2020EGUGA..22.3341T    Altcode:
  For better estimating the drag force acting on coronal mass ejections
  (CMEs) in interplanetary space and ram-pressure at planets, improved
  knowledge of the evolution of CME density/mass is highly valuable. We
  investigate a sample of 29 well observed CME-ICME events, for which
  we determine the de-projected 3D mass (STEREO-A and -B data), and the
  CME volume using GCS modeling (STEREO, SoHO). Expanding the volume to
  1AU distance, we derive the density and compare the results to in-situ
  proton density measurements separately for the ICME sheath and magnetic
  structure. A fair agreement between calculated and measured density is
  derived for the magnetic structure as well for the sheath if taking
  into account mass pile up of solar wind plasma. We give evidence and
  observational assessment that during the interplanetary propagation
  of a CME 1) the magnetic structure has rather constant mass and 2)
  the sheath region at the front of the driver is formed from piled-up
  mass that is rather depending on the solar wind density ahead of the
  CME, than on the CME speed.

---------------------------------------------------------
Title: On the Interaction of Galactic Cosmic Rays with Heliospheric
    Shocks During Forbush Decreases
Authors: Kirin, Anamarija; Vršnak, Bojan; Dumbović, Mateja; Heber,
   Bernd
2020SoPh..295...28K    Altcode: 2020arXiv200209454K
  Forbush decreases (FDs) are depletions in the galactic cosmic ray
  (GCR) count rate that last typically for about a week and can be
  caused by coronal mass ejections (CMEs) or corotating interacting
  regions (CIRs). Fast CMEs that drive shocks cause large FDs that
  often show a two-step decrease where the first step is attributed to
  the shock/sheath region, while the second step is attributed to the
  closed magnetic structure. Since the difference in size of shock and
  sheath region is significant, and since there are observed effects
  that can be related to shocks and not necessarily to the sheath region
  we expect that the physical mechanisms governing the interaction with
  GCRs in these two regions are different. We therefore aim to analyze
  interaction of GCRs with heliospheric shocks only. We approximate the
  shock by a structure where the magnetic field linearly changes with
  position within this structure. We assume protons of different energy,
  different pitch angle and different incoming direction. We also vary the
  shock parameters such as the magnetic field strength and orientation,
  as well as the shock thickness. The results demonstrate that protons
  with higher energies are less likely to be reflected. Also, thicker
  shocks and shocks with stronger field reflect protons more efficiently.

---------------------------------------------------------
Title: Genesis and impulsive evolution of the fast CME associated
    with the X8.2 flare on 2017 September 10
Authors: Veronig, A.; Podladchikova, T.; Dissauer, K.; Temmer, M.;
   Seaton, D. B.; Long, D.; Guo, J.; Vrsnak, B.; Harra, L. K.; Kliem, B.
2019AGUFMSH13A..02V    Altcode:
  The X8.2 event of 2017 September 10 provides unique observations to
  study the genesis, magnetic morphology, impulsive dynamics and shock
  formation in a very fast coronal mass ejection (CME). As will be
  discussed in this presentation, fundamental insight in the processes
  of magnetic reconnection, CME acceleration and shock formation are
  provided through EUV observations of the middle corona. <P />Combining
  the large field-of-view and high-cadence imagery from GOES-16/SUVI
  and SDO/AIA EUV, respectively, we identify a hot (T ≈ 10-15 MK)
  bright rim around a quickly expanding cavity, embedded inside a much
  larger CME shell (T ≈ 1-2 MK). The CME shell develops from a dense
  set of large AR loops (&gt;0.5Rs) and seamlessly evolves into the
  CME front observed in LASCO C2. The strong lateral overexpansion
  of the CME shell acts as a piston initiating the fast and globally
  propagating EUV shock wave. The hot cavity rim is demonstrated to be
  a manifestation of the dominantly poloidal flux and frozen-in plasma
  added to the rising flux rope by magnetic reconnection in the current
  sheet beneath. The same structure is later observed as the core of the
  white-light CME, challenging the traditional interpretation of the CME
  three-part morphology (Veronig et al. 2018). <P />The large amount of
  added magnetic flux suggested by these observations can explain the
  extreme accelerations of the radial and lateral expansion of the CME
  shell and cavity, all reaching values up to 5-10 km s<SUP>-2</SUP>. The
  acceleration peaks occur simultaneously with the first RHESSI 100-300
  keV hard X-ray burst of the associated flare, further underlining the
  importance of the reconnection process for the impulsive CME evolution
  in the low and middle corona.

---------------------------------------------------------
Title: Heliospheric Evolution of Magnetic Clouds
Authors: Vršnak, B.; Amerstorfer, T.; Dumbović, M.; Leitner, M.;
   Veronig, A. M.; Temmer, M.; Möstl, C.; Amerstorfer, U. V.; Farrugia,
   C. J.; Galvin, A. B.
2019ApJ...877...77V    Altcode: 2019arXiv190408266V
  The interplanetary evolution of 11 magnetic clouds (MCs) recorded by at
  least two radially aligned spacecraft is studied. The in situ magnetic
  field measurements are fitted to a cylindrically symmetric Gold-Hoyle
  force-free uniform-twist flux-rope configuration. The analysis
  reveals that in a statistical sense, the expansion of the studied
  MCs is compatible with self-similar behavior. However, individual
  events expose a large scatter of expansion rates, ranging from very
  weak to very strong expansion. Individually, only four events show an
  expansion rate compatible with isotropic self-similar expansion. The
  results indicate that the expansion has to be much stronger when
  the MCs are still close to the Sun than in the studied 0.47-4.8 au
  distance range. The evolution of the magnetic field strength shows a
  large deviation from the behavior expected for the case of isotropic
  self-similar expansion. In the statistical sense, as well as in most
  of the individual events, the inferred magnetic field decreases much
  slower than expected. Only three events show behavior compatible
  with self-similar expansion. There is also a discrepancy between the
  magnetic field decrease and the increase of the MC size, indicating that
  magnetic reconnection and geometrical deformations play a significant
  role in the MC evolution. About half of the events show a decay of the
  electric current as expected for self-similar expansion. Statistically,
  the inferred axial magnetic flux is broadly consistent with remaining
  constant. However, events characterized by a large magnetic flux show
  a clear tendency toward decreasing flux.

---------------------------------------------------------
Title: Genesis, magnetic morphology and impulsive evolution of
    the coronal mass ejection associated with the X8.2 flare on 2017
    September 10
Authors: Veronig, Astrid; Podladchikova, Tatiana; Dissauer, Karin;
   Temmer, Manuela; Seaton, Daniel; Long, David; Guo, Jingnan; Vrsnak,
   Bojan; Harra, Louise; Kliem, Bernhard
2019EGUGA..21.9243V    Altcode:
  The extreme X8.2 event of 2017 September 10 provides unique observations
  to study the genesis, magnetic morphology, impulsive dynamics and
  shock formation in a very fast coronal mass ejection (CME). Combining
  GOES-16/SUVI and SDO/AIA EUV imagery, we identify a hot (T ≈ 10-15
  MK) bright rim around a quickly expanding cavity, embedded inside a
  much larger CME shell (T ≈ 1-2 MK). The CME shell develops from a
  dense set of large AR loops (&gt;0.5Rs) and seamlessly evolves into
  the CME front observed in LASCO C2. The strong lateral overexpansion
  of the CME shell acts as a piston initiating the fast EUV shock
  wave. The hot cavity rim is demonstrated to be a manifestation of
  the dominantly poloidal flux and frozen-in plasma added to the rising
  flux rope by magnetic reconnection in the current sheet beneath. The
  same structure is later observed as the core of the white-light CME,
  challenging the traditional interpretation of the CME three-part
  morphology. The large amount of added magnetic flux suggested by these
  observations explains the extreme accelerations of the radial and
  lateral expansion of the CME shell and cavity, all reaching values
  up to 5-10 km s-2. The acceleration peaks occur simultaneously with
  the first RHESSI 100-300 keV hard X-ray burst of the associated flare,
  further underlining the importance of the reconnection process for the
  impulsive CME evolution. Finally, the much higher radial propagation
  speed of the flux rope in relation to the CME shell causes a distinct
  deformation of the white-light CME front and shock.

---------------------------------------------------------
Title: Observational assessment on CME mass pile up in interplanetary
    space
Authors: Temmer, Manuela; Holzknecht, Lukas; Dumbovic, Mateja;
   Vrsnak, Bojan
2019EGUGA..21.9578T    Altcode:
  Coronal mass ejections (CMEs) propagating in the heliosphere are
  exposed to a drag force due to the ambient solar wind. Mass pile-up
  in interplanetary space can have strong effects on the drag force,
  and with that on the CME propagation time and energy input to the
  magnetosphere. For a sample of well observed events, we determine
  the de-projected 3D mass and its evolution up to a distance range
  of about 15Rs using combined STEREO-SECCHI COR1 and COR2 data, for
  which no pile-up at the CME front is found (see also Bein et al.,
  2013). Applying the GCS forward fitting model (Thernisien et al., 2006,
  2009) on COR2 data, we obtain the volume of the CMEs. Working under the
  assumption that the CME mass is constant beyond 15Rs and that the CME
  undergoes self-similar expansion, we estimate the CME density at the
  distance of 1AU. The results are compared to in-situ proton density
  data measured for the associated ICME's sheath and magnetic structure
  for which we derive a trend towards a mass increase at the CME front.

---------------------------------------------------------
Title: Study of Interplanetary CMEs/Shocks During Solar Cycle 24
Using Drag-Based Model: The Role of Solar Wind
Authors: Suresh, K.; Prasanna Subramanian, S.; Shanmugaraju, A.;
   Vršnak, Bojan; Umapathy, S.
2019SoPh..294...47S    Altcode:
  In this paper we analyze a set of 27 fast interplanetary coronal mass
  ejections (ICMEs) observed during the period January 2010 - December
  2013 in Solar Cycle 24. The arrivals of interplanetary shocks and
  CMEs at 1 AU are found from OMNI spacecraft high resolution data
  and their travel times are compared with Empirical Shock Arrival
  (ESA; Gopalswamy et al. in Adv. Space Res.36, 2289, 2005) and Drag
  Based Model (DBM; Vršnak et al. in Solar Phys.285, 295, 2013). The
  analysis of the transit time, deceleration, and drag parameter is used
  to examine the role of the solar-wind characteristics in the dynamics
  of ICMEs. The obtained ICME parameters (deceleration, drag parameter)
  are compared with the decelerated events (34 of 91 events in Solar
  Cycle 23) from the study of Manoharan et al. (J. Geophy. Res.109,
  A06109, 2004). The interplanetary (IP) deceleration shows similar
  trend between the cycles. Though the Cycle 24 has weak solar wind,
  it does not affect the arrival time behavior. It is concluded that
  the solar-wind behavior is considered to be the same in Cycles 23
  and 24 for ICMEs. The IP drag parameter is linearly correlated with
  CME initial speed. The p-value between CME speed and drag parameter
  suggests that they are highly significant. The important result of the
  study is that the solar wind showed a similar kind of drag effect for
  the propagating CMEs in both cycles.

---------------------------------------------------------
Title: Multiple EUV wave reflection from a coronal hole
Authors: Podladchikova, Tatiana; Veronig, Astrid M.; Podladchikova,
   Olena; Dissauer, Karin; Vršnak, Bojan; Saqri, Jonas; Piantschitsch,
   Isabell; Temmer, Manuela
2019EGUGA..21.9793P    Altcode:
  EUV waves are large-scale propagating disturbances in the solar corona
  initiated by coronal mass ejections. We investigate the multiple EUV
  wave reflections at a coronal hole boundary, as observed by SDO/AIA on 1
  April 2017. The EUV wave originates from Active Region (AR) 12645 close
  to the disk center and propagates toward the south polar coronal hole
  with an average velocity of 430 km/s. The interaction of the EUV wave
  with the coronal hole, which represents a region of high Alfven speed,
  is observed as a splitting into two wave components: one continues
  propagation inside the coronal hole with an increased velocity of 850
  km/s (transmitted wave), while the other one moves back toward the AR,
  also with an increased velocity of 600 km/s (reflected wave). The
  reflected EUV wave is subsequently reflected again from the AR and
  propagates toward the coronal hole with an average velocity of 350
  km/s, where it is reflected for the second time at the coronal hole
  boundary and propagates again toward the AR with a velocity of 300
  km/s. These events are observed over an interval of 40 minutes. The
  high cadence SDO imagery allows us to study in detail the kinematics
  of the direct and multiple times reflected EUV wave. In addition, its
  multi-wavelength EUV imagery allows us to derive the plasma properties
  of the corona and the EUV wave pulse via Differential Emission Measure
  analysis. These results are used to compare the observed characteristics
  of the wave interaction with the coronal hole with simulations.

---------------------------------------------------------
Title: Gradual pre-eruptive phase of solar coronal eruptions
Authors: Vršnak, Bojan
2019FrASS...6...28V    Altcode:
  Physical background of the evolution of a coronal magnetic flux rope
  embedded in the magnetic arcade during the gradual-rise pre-eruptive
  stage is studied. It is assumed that this stage represents an
  externyly-driven evolution of the preeruptive structure through a
  series of quasi-equilibrium states, until a point when system losses
  equilibrium and erupts. In particular, three driving processes are
  considered: twisting motions of the flux-rope footpoints, emergence
  of new magnetic flux beneath the flux rope, and the mass leakage down
  the flux-rope legs. For that purpose, an analytical flux-rope model is
  employed, to inspect how fast the equilibrium height of the structure
  rises due to the increase of the poloidal-toaxial field ratio, the
  increase of axial electric current, and the decrease of mass. It is
  shown that the flux-rope twisting itself is not sufficient to reproduce
  the rising speeds observed during the pre-eruptive stage. Yet, it
  is essential for the loss-ofequilibrium process. On the other hand,
  the considered emerging flux and the mass loss processes reproduce
  well the rate at which the pre-eruptive structure rises before the
  main acceleration stage of the eruption sets in.

---------------------------------------------------------
Title: The Physical Processes of CME/ICME Evolution
Authors: Manchester, Ward, IV; Kilpua, Emilia K. J.; Liu, Ying D.;
   Lugaz, Noé; Riley, Pete; Török, Tibor; Vršnak, Bojan
2019sfsw.book..165M    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: The Origin, Early Evolution and Predictability of Solar
    Eruptions
Authors: Green, Lucie M.; Török, Tibor; Vršnak, Bojan; Manchester,
   Ward, IV; Veronig, Astrid
2019sfsw.book..113G    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Genesis and Impulsive Evolution of the 2017 September 10
    Coronal Mass Ejection
Authors: Veronig, Astrid M.; Podladchikova, Tatiana; Dissauer, Karin;
   Temmer, Manuela; Seaton, Daniel B.; Long, David; Guo, Jingnan; Vršnak,
   Bojan; Harra, Louise; Kliem, Bernhard
2018ApJ...868..107V    Altcode: 2018arXiv181009320V
  The X8.2 event of 2017 September 10 provides unique observations
  to study the genesis, magnetic morphology, and impulsive dynamics
  of a very fast coronal mass ejection (CME). Combining GOES-16/SUVI
  and SDO/AIA EUV imagery, we identify a hot (T ≈ 10-15 MK) bright
  rim around a quickly expanding cavity, embedded inside a much larger
  CME shell (T ≈ 1-2 MK). The CME shell develops from a dense set of
  large AR loops (≳0.5R <SUB> s </SUB>) and seamlessly evolves into
  the CME front observed in LASCO C2. The strong lateral overexpansion
  of the CME shell acts as a piston initiating the fast EUV wave. The
  hot cavity rim is demonstrated to be a manifestation of the dominantly
  poloidal flux and frozen-in plasma added to the rising flux rope by
  magnetic reconnection in the current sheet beneath. The same structure
  is later observed as the core of the white-light CME, challenging the
  traditional interpretation of the CME three-part morphology. The large
  amount of added magnetic flux suggested by these observations explains
  the extreme accelerations of the radial and lateral expansion of the CME
  shell and cavity, all reaching values of 5-10 km s<SUP>-2</SUP>. The
  acceleration peaks occur simultaneously with the first RHESSI 100-300
  keV hard X-ray burst of the associated flare, further underlining
  the importance of the reconnection process for the impulsive CME
  evolution. Finally, the much higher radial propagation speed of the
  flux rope in relation to the CME shell causes a distinct deformation
  of the white-light CME front and shock.

---------------------------------------------------------
Title: Evolution of flux rope, CME and associated EUV wave in the
    10-Sep-2018 X8.2 event
Authors: Podladchikova, Tatiana; Veronig, Astrid M.; Dissauer, Karin;
   Temmer, Manuela; Seaton, Daniel B.; Long, David; Guo, Jingnan; Vršnak,
   Bojan; Harra, Louise; Kliem, Bernhard
2018csc..confE..38P    Altcode:
  We combine the high-cadence and large field-of-view EUV imagery of
  the Atmospheric Imaging Assembly (AIA) onboard SDO and the Solar
  Ultraviolet Imager (SUVI) onboard GOES-16 to study the origin and
  impulsive evolution of the fast CME that originated in the September
  10th 2017 X8.2 event as well as the initiation of the associated EUV
  wave. In the LASCO field-of-view, the CME reveals speeds &gt;3000
  km/s. In the low-to-mid corona, it shows a distinct bubble in the EUV
  imagery that reveals a significant lateral overexpansion. In addition,
  is also shows a distinct expanding cavity that is interpreted as
  manifestation of the flux rope driving the eruption. We present a method
  to automatically identify and segment the CME bubble in SUVI images and
  to derive its radial and lateral evolution up to about 2 solar radii,
  in terms of velocity and acceleration. These measurements are set into
  context with the evolution of the embedded flux rope/cavity observed by
  AIA. The observations show clear signatures of new poloidal flux added
  to the flux rope by magnetic reconnection in the current sheet beneath
  the eruptive structure, which is important for the high accelerations
  observed in this event. The radial propagation of the CME shell revealed
  a peak value of the acceleration of about 5.3 km/s2, whereas the lateral
  expansion reached a peak value of 10.1 km/s2, which is the largest value
  reported so far. The flux rope/cavity reveals a radial acceleration of
  6.7 km/s2 and lateral acceleration of 5.3 km/s2. We note that at this
  early evolution phase, the speed of the cavity/flux rope is higher
  than that of the CME bubble (front). The EUV wave associated with
  this eruption was observed by AIA, SUVI and STEREO-A EUVI, which had
  a separation angle with Earth of 128°, and the common field of view
  of the spacecraft was 52°. AIA and SUVI images above the solar limb
  reveal the initiation of the EUV wave by the accelerating flanks of
  the CME bubble, followed by detachment and propagation of the wave
  with a speed of 1100 km/s. The EUV wave shows a global propagation
  over the full hemisphere visible to Earth view as well as into the
  STEREO-A field-of-view. We study the propagation and kinematics of
  the direct as well as the various reflected and refracted EUV wave
  components on the solar sphere, finding speeds in the range from 370
  to 1010 km/s. Finally, we note that this EUV wave is also distinct as
  it reveals propagation and transmission through the polar coronal holes.

---------------------------------------------------------
Title: Photospheric and chromospheric observations with solar
    telescope at Hvar Observatory
Authors: Calogovic, J.; Brajsa, Roman; Vrsnak, Bojan; Dumbovic,
   Mateja; Skokic, Ivica
2018cosp...42E.496C    Altcode:
  The double solar telescope at the Hvar Observatory consists of two
  Carl Zeiss refractors, one with 217 mm objective diameter used for
  photospheric observations and the second one with 130 mm objective used
  for chromospheric observations. Hvar solar telescope aims to produce
  the high-resolution and high-cadence imaging of active regions on the
  Sun using a field of view of about 11 arcmin for the photosphere and
  7 arcmin for the chromosphere. The modern Pulnix TM-4200GE 12-bit 4
  megapixel CCD cameras recording seven frames per second together with
  the software that automatically selects the sharpest frames allow
  to study the rapid changes on the Sun in great detail. High-cadence
  ground-based observations are an important tool to identify and study
  solar flares, filaments and other solar phenomena that are associated
  with coronal mass ejections and their propagation to the Earth. Aiming
  to improve the space weather forecasts using ground-based observations,
  we compiled the catalogue of Hvar solar telescope observations in the
  solar cycle 24. In addition, expansion of this catalogue in future
  will be used for comparison with ALMA-SSALMON observations. This work
  has been supported by the Croatian Science Foundation project 6212
  "Solar and Stellar Variability" (SOLSTEL).

---------------------------------------------------------
Title: The possible impact of solar activity on extratropical
    cyclone activity
Authors: Calogovic, J.; Vrsnak, Bojan; Dumbovic, Mateja; Rieder, Harald
2018cosp...42E.497C    Altcode:
  The mechanism based on the global electric circuit (GEC) flowing
  vertically from the ionosphere to the Earth's surface could potentially
  provide the link between the solar modulated energetic particles
  and Earth's weather and climate. Cosmic ray induced atmospheric
  ionization modulates the vertical current density (Jz) and introduces
  the changes in GEC that could alter the microphysical properties of
  the clouds (Tinsley, 2008). Due to the complexity and scale of the
  GEC and its feedbacks, possible implications and importance of this
  mechanism are still mostly unknown. One of the possible feedbacks
  to GEC alteration could be the proces of storm invigoration and
  occurrence of extratropical cyclones. Using 6-hourly sea level pressure
  (SLP) fields from the ERA-Interim data, extratropical cyclones are
  identified by tracking their low-pressure centers. Daily timescale
  epoch-superpositional (composite) analysis is performed to analyze
  the occurrence of extratropical cyclones during the biggest Forbush
  decrease events in the last three solar cycles. Since autocorrelations
  are the common feature of geophysical data, to test the significance
  of results we use robust Monte Carlo significance testing. This work
  has been supported by the Croatian Science Foundation project 6212
  "Solar and Stellar Variability" (SOLSTEL).

---------------------------------------------------------
Title: Forbush decrease model for expanding CMEs (ForbMod)
Authors: Dumbovic, Mateja; Möstl, Christian; Guo, Jingnan; Heber,
   Bernd; Vrsnak, Bojan; Temmer, Manuela
2018cosp...42E.917D    Altcode:
  Forbush decreases (FDs) can be used as one of the "signatures" of an
  ICME passage. An analytical diffusion-expansion FD model (ForbMod) was
  developed that is based on the widely used approach of an initially
  empty, closed magnetic structure (i.e. flux rope) that fills up
  slowly with particles by diffusion perpendicular to the magnetic
  field of the flux rope. In our approach the FD amplitude is not only
  determined by the diffusion process but also by the expansion of the
  flux rope. While the first process leads to a smaller amplitude the
  second one leads again to a larger effect. Remote CME observations
  and 3D reconstruction is used to constrain initial and boundary
  conditions. CME evolutionary properties are taken into account by
  incorporating the flux rope expansion. Several options of flux rope
  expansion are regarded as competing mechanism to diffusion, which can
  lead to different FD characteristics, and forward modelling is used
  to analyse flux rope expansion and further constrain the model. In
  testing the model, a number of spacecraft and planetary observation is
  utilised, including those by the Radiation Assessment Detector aboard
  the Mars Rover Curiosity. This project has received funding from the
  European Union's Horizon 2020 research and innovation programme under
  the Marie Sk_odowska-Curie grant agreement No 745782.

---------------------------------------------------------
Title: Type II solar radio burst band-splitting: Measure of coronal
    magnetic field strength
Authors: Mahrous, Ayman; Alielden, Khaled; Vršnak, Bojan; Youssef,
   Mohamed
2018JASTP.172...75M    Altcode:
  Studies of the relationship between solar radio bursts and CMEs are
  essential for understanding of the nature of type II bursts. In this
  study, we examine the type II solar radio burst recorded on 16 March
  2016 by the Learmonth radio spectrograph and compare its characteristics
  with the kinematics of the associated CMEs observed by STEREO and
  SOHO spacecraft. The burst showed a well-defined band-split, which was
  used to estimate the magnetic field strength in the solar corona. The
  magnetic field decreases from ≈ 4 G at R ≈ 2.6 R<SUB>⊙</SUB> to
  0.62 G at R ≈ 3.77 R<SUB>⊙</SUB> depending on the coronal electron
  density model employed. We found that two CMEs occurred successively in
  a 4-h interval. During this interval, a type II radio burst occurred,
  lasting for about 10 min. Tracking of the shock that produced type II
  burst and comparison with the CMEs heights as observed by STEREO and
  SOHO spacecraft help us to deduce the driver of the shock. According
  to the analysis, the type II burst occurrence was associated with the
  interaction of the shock driven by the second CME with a streamer
  located south of the first CME, since that the type II band-split
  significantly increased during the shock-streamer interaction. Our
  results show that the analysis of the type II burst band-split
  supplemented by the coronagraphic observations of the corona is an
  important tool for the understanding of the coronal eruptive processes.

---------------------------------------------------------
Title: Drag-based ensemble model (DBEM)
Authors: Dumbovic, Mateja; Möstl, Christian; Mays, M. Leila; Vrsnak,
   Bojan; Veronig, Astrid; Salogovic, Jara; Piantschitsch, Isabell;
   Amerstorfer, Tanja; Temmer, Manuela; Sudar, Davor
2018cosp...42E.918D    Altcode:
  The drag-based model (DBM) for heliospheric propagation of ICMEs is
  a widely used simple analytical model which can predict ICME arrival
  time and speed at a given heliospheric distance (Vr_nak et al.,
  2013, SolPhys). It is based on the assumption that the heliospheric
  propagation of ICMEs, is solely under the influence of MHD drag,
  where ICME propagation is determined based on CME properties as
  well as the properties of the ambient solar wind. The current
  version of the DBM is operational as part of ESA's SSA programme
  (http://swe.ssa.esa.int/web/guest/graz-dbm-federated). The DBM takes
  into account the ICME geometry to track the whole leading edge of an
  ICME, it can estimate whether or not an ICME will reach the observer
  and calculate the transit time and impact speed. To estimate the
  uncertainty for a single event, Drag-Based Ensemble Model (DBEM) was
  developed (Dumbovic et al., 2018, ApJ) which utilizes an ensemble of the
  observation-based CME input and synthetic values of the ambient solar
  wind speed and drag parameter. Using multiple runs with different input
  parameters, distributions of predicted arrival times and speeds are
  obtained allowing to forecast the confidence in the likelihood of the
  ICME arrival. The DBEM was further developed to an on-line application
  to provide the real-time CME forecast, which is currently in a test
  phase, and will soon be a part of ESA-SSA Heliospheric Weather Expert
  Service Group (http://swe.ssa.esa.int/heliospheric-weather). We test
  the model and the on-line application using observations and compare
  the performance with other CME propagation models.

---------------------------------------------------------
Title: An Analytical Diffusion-Expansion Model for Forbush Decreases
    Caused by Flux Ropes
Authors: Dumbović, Mateja; Heber, Bernd; Vršnak, Bojan; Temmer,
   Manuela; Kirin, Anamarija
2018ApJ...860...71D    Altcode: 2018arXiv180500916D
  We present an analytical diffusion-expansion Forbush decrease (FD)
  model ForbMod, which is based on the widely used approach of an
  initially empty, closed magnetic structure (i.e., flux rope) that
  fills up slowly with particles by perpendicular diffusion. The model
  is restricted to explaining only the depression caused by the magnetic
  structure of the interplanetary coronal mass ejection (ICME). We use
  remote CME observations and a 3D reconstruction method (the graduated
  cylindrical shell method) to constrain initial boundary conditions
  of the FD model and take into account CME evolutionary properties by
  incorporating flux rope expansion. Several flux rope expansion modes
  are considered, which can lead to different FD characteristics. In
  general, the model is qualitatively in agreement with observations,
  whereas quantitative agreement depends on the diffusion coefficient and
  the expansion properties (interplay of the diffusion and expansion). A
  case study was performed to explain the FD observed on 2014 May 30. The
  observed FD was fitted quite well by ForbMod for all expansion modes
  using only the diffusion coefficient as a free parameter, where the
  diffusion parameter was found to correspond to an expected range of
  values. Our study shows that, in general, the model is able to explain
  the global properties of an FD caused by a flux rope and can thus be
  used to help understand the underlying physics in case studies.

---------------------------------------------------------
Title: Numerical Simulation of Coronal Waves Interacting with Coronal
    Holes. III. Dependence on Initial Amplitude of the Incoming Wave
Authors: Piantschitsch, Isabell; Vršnak, Bojan; Hanslmeier, Arnold;
   Lemmerer, Birgit; Veronig, Astrid; Hernandez-Perez, Aaron; Čalogović,
   Jaša
2018ApJ...860...24P    Altcode: 2018arXiv181112735P
  We performed 2.5D magnetohydrodynamic (MHD) simulations showing the
  propagation of fast-mode MHD waves of different initial amplitudes and
  their interaction with a coronal hole (CH), using our newly developed
  numerical code. We find that this interaction results in, first, the
  formation of reflected, traversing, and transmitted waves (collectively,
  secondary waves) and, second, in the appearance of stationary features
  at the CH boundary. Moreover, we observe a density depletion that
  is moving in the opposite direction of the incoming wave. We find a
  correlation between the initial amplitude of the incoming wave and
  the amplitudes of the secondary waves as well as the peak values of
  the stationary features. Additionally, we compare the phase speed of
  the secondary waves and the lifetime of the stationary features to
  observations. Both effects obtained in the simulation, the evolution
  of secondary waves, as well as the formation of stationary fronts at
  the CH boundary, strongly support the theory that coronal waves are
  fast-mode MHD waves.

---------------------------------------------------------
Title: Using Forbush decreases to derive the transit time of ICMEs
    propagating from 1 AU to Mars
Authors: von Forstner, Johan; Guo, Jingnan; Wimmer-Schweingruber,
   Robert F.; Hassler, Donald M.; Temmer, Manuela; Dumbović, Mateja;
   Jian, Lan K.; Appel, Jan K.; Čalogović, Jaša; Ehresmann, Bent;
   Heber, Bernd; Lohf, Henning; Posner, Arik; Vršnak, Bojan; Zeitlin,
   Cary J.
2018EGUGA..20.9306V    Altcode:
  The propagation of 15 interplanetary coronal mass ejections (ICMEs) from
  Earth's orbit (1 AU) to Mars (∼1.5 AU) has been studied with their
  propagation speed estimated from both measurements and simulations. The
  enhancement of magnetic fields related to ICMEs and their shock fronts
  cause the so-called Forbush decrease, which can be detected as a
  reduction of galactic cosmic ray (GCR) intensity measured on-ground
  or on a spacecraft. This effect can be used to detect the passage of
  ICMEs at various locations in the heliosphere, for example at Earth
  (using neutron monitors), the STEREO A and B spacecraft (HET) as well
  the on the surface of Mars using the Radiation Assessment Detector
  (RAD) instrument on the Mars Science Laboratory (MSL) rover. A set of
  ICME events has been selected during the periods when Earth (or STEREO
  A or B) and Mars locations were nearly aligned on the same side of the
  Sun in the ecliptic plane (so-called opposition phase). Such lineups
  allow us to estimate the ICMEs' transit times between 1 and 1.5 AU by
  determining the time delay between the corresponding Forbush decreases
  measured at each location. We investigate the evolution of the ICME
  propagation speeds before and after passing Earth's orbit and find
  that their deceleration due to interaction with the ambient solar
  wind may continue beyond 1 AU. We also find a substantial variance of
  the speed evolution among different events revealing the dynamic and
  diverse nature of eruptive solar events. Furthermore, the results are
  compared to simulation data obtained from two CME propagation models,
  namely the Drag-Based Model and ENLIL plus cone model.

---------------------------------------------------------
Title: Forbush decrease model for expanding CMEs (ForbMod)
Authors: Dumbovic, Mateja; Temmer, Manuela; Guo, Jingnan; Heber,
   Bernd; Möstl, Christian; Vrsnak, Bojan
2018EGUGA..2015396D    Altcode:
  The Project ForbMod aims to unravel how galactic cosmic rays are
  influenced by solar storms in the inner solar system (Sun to Mars)
  by developing a new model and utilizing a number of spacecraft and
  planetary observation, including those by the Radiation Assessment
  Detector aboard the Mars Rover Curiosity. The project focuses on
  Forbush decreases (FDs) in the galactic cosmic ray flux, which can
  be used as one of the "signatures" of an ICME passage. An analytical
  diffusion-expansion FD model was developed that is based on the
  widely used approach of an initially empty, closed magnetic structure
  (i.e. flux rope) that fills up slowly with particles by perpendicular
  diffusion. Remote CME observations and 3D reconstruction is used to
  constrain initial and boundary conditions. CME evolutionary properties
  are taken into account by incorporating the flux rope expansion. Several
  options of flux rope expansion are regarded as competing mechanism
  to diffusion, which can lead to different FD characteristics. This
  project has received funding from the European Union's Horizon 2020
  research and innovation programme under the Marie Skłodowska-Curie
  grant agreement No 745782.

---------------------------------------------------------
Title: Numerical Simulation of Coronal Waves Interacting with Coronal
    Holes. II. Dependence on Alfvén Speed Inside the Coronal Hole
Authors: Piantschitsch, Isabell; Vršnak, Bojan; Hanslmeier, Arnold;
   Lemmerer, Birgit; Veronig, Astrid; Hernandez-Perez, Aaron; Čalogović,
   Jaša
2018ApJ...857..130P    Altcode: 2018arXiv181112726P
  We used our newly developed magnetohydrodynamic (MHD) code to perform
  2.5D simulations of a fast-mode MHD wave interacting with coronal holes
  (CHs) of varying Alfvén speed that result from assuming different
  CH densities. We find that this interaction leads to effects like
  reflection, transmission, stationary fronts at the CH boundary,
  and the formation of a density depletion that moves in the opposite
  direction to the incoming wave. We compare these effects with regard
  to the different CH densities and present a comprehensive analysis of
  morphology and kinematics of the associated secondary waves. We find
  that the density value inside the CH influences the phase speed and
  the amplitude values of density and magnetic field for all different
  secondary waves. Moreover, we observe a correlation between the
  CH density and the peak values of the stationary fronts at the CH
  boundary. The findings of reflection and transmission on the one hand
  and the formation of stationary fronts caused by the interaction of
  MHD waves with CHs on the other hand strongly support the theory that
  large-scale disturbances in the corona are fast-mode MHD waves.

---------------------------------------------------------
Title: The Dependence of the Peak Velocity of High-Speed Solar Wind
    Streams as Measured in the Ecliptic by ACE and the STEREO satellites
    on the Area and Co-latitude of Their Solar Source Coronal Holes
Authors: Hofmeister, Stefan J.; Veronig, Astrid; Temmer, Manuela;
   Vennerstrom, Susanne; Heber, Bernd; Vršnak, Bojan
2018JGRA..123.1738H    Altcode: 2018arXiv180409579H
  We study the properties of 115 coronal holes in the time range
  from August 2010 to March 2017, the peak velocities of the
  corresponding high-speed streams as measured in the ecliptic at 1
  AU, and the corresponding changes of the Kp index as marker of their
  geoeffectiveness. We find that the peak velocities of high-speed streams
  depend strongly on both the areas and the co-latitudes of their solar
  source coronal holes with regard to the heliospheric latitude of
  the satellites. Therefore, the co-latitude of their source coronal
  hole is an important parameter for the prediction of the high-speed
  stream properties near the Earth. We derive the largest solar wind
  peak velocities normalized to the coronal hole areas for coronal holes
  located near the solar equator and that they linearly decrease with
  increasing latitudes of the coronal holes. For coronal holes located
  at latitudes ≳60°, they turn statistically to zero, indicating
  that the associated high-speed streams have a high chance to miss the
  Earth. Similarly, the Kp index per coronal hole area is highest for the
  coronal holes located near the solar equator and strongly decreases
  with increasing latitudes of the coronal holes. We interpret these
  results as an effect of the three-dimensional propagation of high-speed
  streams in the heliosphere; that is, high-speed streams arising from
  coronal holes near the solar equator propagate in direction toward and
  directly hit the Earth, whereas solar wind streams arising from coronal
  holes at higher solar latitudes only graze or even miss the Earth.

---------------------------------------------------------
Title: The Origin, Early Evolution and Predictability of Solar
    Eruptions
Authors: Green, Lucie M.; Török, Tibor; Vršnak, Bojan; Manchester,
   Ward; Veronig, Astrid
2018SSRv..214...46G    Altcode: 2018arXiv180104608G
  Coronal mass ejections (CMEs) were discovered in the early 1970s
  when space-borne coronagraphs revealed that eruptions of plasma
  are ejected from the Sun. Today, it is known that the Sun produces
  eruptive flares, filament eruptions, coronal mass ejections and failed
  eruptions; all thought to be due to a release of energy stored in
  the coronal magnetic field during its drastic reconfiguration. This
  review discusses the observations and physical mechanisms behind this
  eruptive activity, with a view to making an assessment of the current
  capability of forecasting these events for space weather risk and impact
  mitigation. Whilst a wealth of observations exist, and detailed models
  have been developed, there still exists a need to draw these approaches
  together. In particular more realistic models are encouraged in order
  to asses the full range of complexity of the solar atmosphere and the
  criteria for which an eruption is formed. From the observational side,
  a more detailed understanding of the role of photospheric flows and
  reconnection is needed in order to identify the evolutionary path that
  ultimately means a magnetic structure will erupt.

---------------------------------------------------------
Title: The Drag-based Ensemble Model (DBEM) for Coronal Mass Ejection
    Propagation
Authors: Dumbović, Mateja; Čalogović, Jaša; Vršnak, Bojan; Temmer,
   Manuela; Mays, M. Leila; Veronig, Astrid; Piantschitsch, Isabell
2018ApJ...854..180D    Altcode: 2018arXiv180107473D
  The drag-based model for heliospheric propagation of coronal mass
  ejections (CMEs) is a widely used analytical model that can predict
  CME arrival time and speed at a given heliospheric location. It is
  based on the assumption that the propagation of CMEs in interplanetary
  space is solely under the influence of magnetohydrodynamical drag,
  where CME propagation is determined based on CME initial properties
  as well as the properties of the ambient solar wind. We present
  an upgraded version, the drag-based ensemble model (DBEM), that
  covers ensemble modeling to produce a distribution of possible ICME
  arrival times and speeds. Multiple runs using uncertainty ranges for
  the input values can be performed in almost real-time, within a few
  minutes. This allows us to define the most likely ICME arrival times
  and speeds, quantify prediction uncertainties, and determine forecast
  confidence. The performance of the DBEM is evaluated and compared
  to that of ensemble WSA-ENLIL+Cone model (ENLIL) using the same
  sample of events. It is found that the mean error is ME = -9.7 hr,
  mean absolute error MAE = 14.3 hr, and root mean square error RMSE =
  16.7 hr, which is somewhat higher than, but comparable to ENLIL errors
  (ME = -6.1 hr, MAE = 12.8 hr and RMSE = 14.4 hr). Overall, DBEM and
  ENLIL show a similar performance. Furthermore, we find that in both
  models fast CMEs are predicted to arrive earlier than observed, most
  likely owing to the physical limitations of models, but possibly also
  related to an overestimation of the CME initial speed for fast CMEs.

---------------------------------------------------------
Title: Properties and relationship between solar eruptive flares and
    Coronal Mass Ejections during rising phase of Solar Cycles 23 and 24
Authors: Syed Ibrahim, M.; Shanmugaraju, A.; Moon, Y. -J.; Vrsnak,
   B.; Umapathy, S.
2018AdSpR..61..540S    Altcode:
  Statistical relationship between major flares and the associated CMEs
  during rising phases of Solar Cycles 23 and 24 are studied. Totally
  more than 6000 and 10,000 CMEs were observed by SOHO/LASCO (Solar
  and Heliospheric Observatory/Large Angle Spectrometric Coronagraph)
  during 23rd [May 1996-June 2002] and 24th [December 2008-December 2014]
  solar cycles, respectively. In particular, we studied the relationship
  between properties of flares and CMEs using the limb events (longitude
  70-85°) to avoid projection effects of CMEs and partial occultation of
  flares that occurred near 90°. After selecting a sample of limb flares,
  we used certain spatial and temporal constraints to find the flare-CME
  pairs. Using these constraints, we compiled 129 events in Solar Cycle 23
  and 92 events in Solar Cycle 24. We compared the flare-CME relationship
  in the two solar cycles and no significant differences are found between
  the two cycles. We only found out that the CME mean width was slightly
  larger and the CME mean acceleration was slightly higher in cycle 24,
  and that there was somewhat a better relation between flare flux and
  CME deceleration in cycle 24 than in cycle 23.

---------------------------------------------------------
Title: Using Forbush Decreases to Derive the Transit Time of ICMEs
    Propagating from 1 AU to Mars
Authors: Freiherr von Forstner, Johan L.; Guo, Jingnan;
   Wimmer-Schweingruber, Robert F.; Hassler, Donald M.; Temmer, Manuela;
   Dumbović, Mateja; Jian, Lan K.; Appel, Jan K.; Čalogović, Jaša.;
   Ehresmann, Bent; Heber, Bernd; Lohf, Henning; Posner, Arik; Steigies,
   Christian T.; Vršnak, Bojan; Zeitlin, Cary J.
2018JGRA..123...39F    Altcode: 2017arXiv171207301V
  The propagation of 15 interplanetary coronal mass ejections (ICMEs) from
  Earth's orbit (1 AU) to Mars (∼1.5 AU) has been studied with their
  propagation speed estimated from both measurements and simulations. The
  enhancement of magnetic fields related to ICMEs and their shock fronts
  causes the so-called Forbush decrease, which can be detected as a
  reduction of galactic cosmic rays measured on ground. We have used
  galactic cosmic ray (GCR) data from in situ measurements at Earth, from
  both STEREO A and STEREO B as well as GCR measurements by the Radiation
  Assessment Detector (RAD) instrument on board Mars Science Laboratory
  on the surface of Mars. A set of ICME events has been selected during
  the periods when Earth (or STEREO A or STEREO B) and Mars locations
  were nearly aligned on the same side of the Sun in the ecliptic plane
  (so-called opposition phase). Such lineups allow us to estimate the
  ICMEs' transit times between 1 and 1.5 AU by estimating the delay time
  of the corresponding Forbush decreases measured at each location. We
  investigate the evolution of their propagation speeds before and after
  passing Earth's orbit and find that the deceleration of ICMEs due to
  their interaction with the ambient solar wind may continue beyond 1
  AU. We also find a substantial variance of the speed evolution among
  different events revealing the dynamic and diverse nature of eruptive
  solar events. Furthermore, the results are compared to simulation data
  obtained from two CME propagation models, namely the Drag-Based Model
  and ENLIL plus cone model.

---------------------------------------------------------
Title: CME volume calculation from 3D GCS reconstruction
Authors: Holzknecht, L.; Temmer, M.; Dumbović, M.; Wellenzohn, S.;
   Krikova, K.; Heinemann, S. G.; Rodari, M.; Vršnak, B.; Veronig, A. M.
2018CEAB...42....3H    Altcode: 2019arXiv190411418H
  The mass evolution of a coronal mass ejection (CME) is an important
  parameter characterizing the drag force acting on a CME as it propagates
  through interplanetary space. Spacecraft measure in-situ plasma
  densities of CMEs during crossing events, but for investigating the
  mass evolution, we also need to know the CME geometry, more specific,
  its volume. Having derived the CME volume and mass from remote sensing
  data using 3D reconstructed CME geometry, we can calculate the CME
  density and compare it with in-situ proton density measurements near
  Earth. From that we may draw important conclusions on a possible
  mass increase as the CME interacts with the ambient solar wind in the
  heliosphere. In this paper we will describe in detail the method for
  deriving the CME volume using the graduated cylindrical shell (GCS)
  model tep[][see \ref{fig:GCSModel}]{thernisien06,thernisien09}. We show
  that, assuming self-similar expansion, one can derive the volume of the
  CME from two GCS parameters and that it furthermore can be expressed
  as a function of distance.

---------------------------------------------------------
Title: Multi-spacecraft observations of ICMEs propagating beyond
    Earth orbit during MSL/RAD flight and surface phases
Authors: von Forstner, J.; Guo, J.; Wimmer-Schweingruber, R. F.;
   Hassler, D.; Temmer, M.; Vrsnak, B.; Čalogović, J.; Dumbovic, M.;
   Lohf, H.; Appel, J. K.; Heber, B.; Steigies, C. T.; Zeitlin, C.;
   Ehresmann, B.; Jian, L. K.; Boehm, E.; Boettcher, S. I.; Burmeister,
   S.; Martin-Garcia, C.; Brinza, D. E.; Posner, A.; Reitz, G.; Matthiae,
   D.; Rafkin, S. C.; weigle, G., II; Cucinotta, F.
2017AGUFMSH53A2543V    Altcode:
  The propagation of interplanetary coronal mass ejections (ICMEs)
  between Earth's orbit (1 AU) and Mars ( 1.5 AU) has been studied
  with their propagation speed estimated from both measurements and
  simulations. The enhancement of the magnetic fields related to ICMEs
  and their shock fronts cause so-called Forbush decreases, which can
  be detected as a reduction of galactic cosmic rays measured on-ground
  or on a spacecraft. We have used galactic cosmic ray (GCR) data from
  in-situ measurements at Earth, from both STEREO A and B as well
  as the GCR measurement by the Radiation Assessment Detector (RAD)
  instrument onboard Mars Science Laboratory (MSL) on the surface of
  Mars as well as during its flight to Mars in 2011-2012. A set of ICME
  events has been selected during the periods when Earth (or STEREO A
  or B) and MSL locations were nearly aligned on the same side of the
  Sun in the ecliptic plane (so-called opposition phase). Such lineups
  allow us to estimate the ICMEs' transit times between 1 AU and the
  MSL location by estimating the delay time of the corresponding Forbush
  decreases measured at each location. We investigate the evolution of
  their propagation speeds after passing Earth's orbit and find that the
  deceleration of ICMEs due to their interaction with the ambient solar
  wind continues beyond 1 AU. The results are compared to simulation data
  obtained from two CME propagation models, namely the Drag-Based Model
  (DBM) and the WSA-ENLIL plus cone model.

---------------------------------------------------------
Title: A Numerical Simulation of Coronal Waves Interacting with
    Coronal Holes. I. Basic Features
Authors: Piantschitsch, Isabell; Vršnak, Bojan; Hanslmeier, Arnold;
   Lemmerer, Birgit; Veronig, Astrid; Hernandez-Perez, Aaron; Čalogović,
   Jaša; Žic, Tomislav
2017ApJ...850...88P    Altcode: 2018arXiv181112073P
  We have developed a new numerical code that is able to perform 2.5D
  simulations of a magnetohydrodynamic (MHD) wave propagation in the
  corona, and its interaction with a low-density region, such as a
  coronal hole (CH). We show that the impact of the wave on the CH
  leads to different effects, such as reflection and transmission of the
  incoming wave, stationary features at the CH boundary, or formation
  of a density depletion. We present a comprehensive analysis of the
  morphology and kinematics of primary and secondary waves, I.e.,
  we describe in detail the temporal evolution of density, magnetic
  field, plasma flow velocity, phase speed, and position of the wave
  amplitude. Effects like reflection, refraction, and transmission of
  the wave strongly support the theory that large-scale disturbances
  in the corona are fast MHD waves and distinguish that theory from the
  competing pseudo-wave theory. The formation of stationary bright fronts
  was one of the main reasons for the development of pseudo-waves. Here,
  we show that stationary bright fronts can be produced by interactions
  of an MHD wave with a CH. We find secondary waves that are traversing
  through the CH and we show that one part of these traversing waves
  leaves the CH again, while another part is being reflected at the CH
  boundary inside the CH. We observe a density depletion that is moving
  in the opposite direction of the primary wave propagation. We show
  that the primary wave pushes the CH boundary to the right, caused by
  the wave front exerting dynamic pressure on the CH.

---------------------------------------------------------
Title: The Physical Processes of CME/ICME Evolution
Authors: Manchester, Ward; Kilpua, Emilia K. J.; Liu, Ying D.; Lugaz,
   Noé; Riley, Pete; Török, Tibor; Vršnak, Bojan
2017SSRv..212.1159M    Altcode: 2017SSRv..tmp...90M
  As observed in Thomson-scattered white light, coronal mass ejections
  (CMEs) are manifest as large-scale expulsions of plasma magnetically
  driven from the corona in the most energetic eruptions from the
  Sun. It remains a tantalizing mystery as to how these erupting magnetic
  fields evolve to form the complex structures we observe in the solar
  wind at Earth. Here, we strive to provide a fresh perspective on the
  post-eruption and interplanetary evolution of CMEs, focusing on the
  physical processes that define the many complex interactions of the
  ejected plasma with its surroundings as it departs the corona and
  propagates through the heliosphere. We summarize the ways CMEs and
  their interplanetary CMEs (ICMEs) are rotated, reconfigured, deformed,
  deflected, decelerated and disguised during their journey through the
  solar wind. This study then leads to consideration of how structures
  originating in coronal eruptions can be connected to their far removed
  interplanetary counterparts. Given that ICMEs are the drivers of most
  geomagnetic storms (and the sole driver of extreme storms), this work
  provides a guide to the processes that must be considered in making
  space weather forecasts from remote observations of the corona.

---------------------------------------------------------
Title: Geomagnetic Effects of Corotating Interaction Regions
Authors: Vršnak, Bojan; Dumbović, Mateja; Čalogović, Jaša;
   Verbanac, Giuliana; Poljančić Beljan, Ivana
2017SoPh..292..140V    Altcode:
  We present an analysis of the geoeffectiveness of corotating interaction
  regions (CIRs), employing the data recorded from 25 January to 5 May
  2005 and throughout 2008. These two intervals in the declining phase
  of Solar Cycle 23 are characterised by a particularly low number of
  interplanetary coronal mass ejections (ICMEs). We study in detail how
  four geomagnetic-activity parameters (the Dst, Ap, and AE indices,
  as well as the Dst time derivative, dDst /d t ) are related to three
  CIR-related solar wind parameters (flow speed, V , magnetic field, B ,
  and the convective electric field based on the southward Geocentric
  solar magnetospheric (GSM) magnetic field component, VB<SUB>s</SUB>)
  on a three-hour time resolution. In addition, we quantify statistical
  relationships between the mentioned geomagnetic indices. It is found
  that Dst is correlated best to V , with a correlation coefficient of cc
  ≈0.6 , whereas there is no correlation between dDst /d t and V . The
  Ap and AE indices attain peaks about half a day before the maximum of V
  , with correlation coefficients ranging from cc ≈0.6 to cc ≈0.7 ,
  depending on the sample used. The best correlations of Ap and AE are
  found with VB<SUB>s</SUB> with a delay of 3 h, being characterised
  by cc ≳0.6 . The Dst derivative dDst /d t is also correlated with
  VB<SUB>s</SUB>, but the correlation is significantly weaker cc
  ≈0.4 - 0.5, with a delay of 0 - 3 h, depending on the employed
  sample. Such low values of correlation coefficients indicate that
  there are other significant effects that influence the relationship
  between the considered parameters. The correlation of all studied
  geomagnetic parameters with B are characterised by considerably lower
  correlation coefficients, ranging from cc =0.3 in the case of dDst /d
  t up to cc =0.56 in the case of Ap. It is also shown that peak values
  of geomagnetic indices depend on the duration of the CIR-related
  structures. The Dst is closely correlated with Ap and AE (cc =0.7 ),
  Dst being delayed for about 3 h. On the other hand, dDst /d t peaks
  simultaneously with Ap and AE, with correlation coefficients of 0.48
  and 0.56, respectively. The highest correlation (cc =0.81 ) is found
  for the relationship between Ap and AE.

---------------------------------------------------------
Title: Validation of the CME Geomagnetic Forecast Alerts Under the
    COMESEP Alert System
Authors: Dumbović, Mateja; Srivastava, Nandita; Rao, Yamini K.;
   Vršnak, Bojan; Devos, Andy; Rodriguez, Luciano
2017SoPh..292...96D    Altcode:
  Under the European Union 7th Framework Programme (EU FP7) project
  Coronal Mass Ejections and Solar Energetic Particles (COMESEP,
  http://comesep.aeronomy.be), an automated space weather alert system has
  been developed to forecast solar energetic particles (SEP) and coronal
  mass ejection (CME) risk levels at Earth. The COMESEP alert system
  uses the automated detection tool called Computer Aided CME Tracking
  (CACTus) to detect potentially threatening CMEs, a drag-based model
  (DBM) to predict their arrival, and a CME geoeffectiveness tool (CGFT)
  to predict their geomagnetic impact. Whenever CACTus detects a halo or
  partial halo CME and issues an alert, the DBM calculates its arrival
  time at Earth and the CGFT calculates its geomagnetic risk level. The
  geomagnetic risk level is calculated based on an estimation of the
  CME arrival probability and its likely geoeffectiveness, as well as an
  estimate of the geomagnetic storm duration. We present the evaluation
  of the CME risk level forecast with the COMESEP alert system based on a
  study of geoeffective CMEs observed during 2014. The validation of the
  forecast tool is made by comparing the forecasts with observations. In
  addition, we test the success rate of the automatic forecasts (without
  human intervention) against the forecasts with human intervention using
  advanced versions of the DBM and CGFT (independent tools available at
  the Hvar Observatory website, http://oh.geof.unizg.hr). The results
  indicate that the success rate of the forecast in its current form is
  unacceptably low for a realistic operation system. Human intervention
  improves the forecast, but the false-alarm rate remains unacceptably
  high. We discuss these results and their implications for possible
  improvement of the COMESEP alert system.

---------------------------------------------------------
Title: Investigation on M-class Flare-Associated Coronal Mass
    Ejections with and Without DH Type II Radio Bursts
Authors: Selvarani, G.; Shanmugaraju, A.; Vrsnak, Bojan; Lawrance,
   M. Bendict
2017SoPh..292...74S    Altcode:
  We perform a statistical analysis on 157 M-class soft X-ray flares
  observed during 1997 - 2014 with and without deca-hectometric (DH)
  type II radio bursts aiming at the reasons for the non-occurrence
  of DH type II bursts in certain events. All the selected events are
  associated with halo Coronal Mass Ejections (CMEs) detected by the
  Solar and Heliospheric Observatory (SOHO) / Large Angle Spectrometric
  and COronograph (LASCO). Out of 157 events, 96 (61%; "Group I")
  events are associated with a DH type II burst observed by the Radio
  and Plasma Wave (WAVES) experiment onboard the Wind spacecraft and 61
  (39%; "Group II") events occur without a DH type II burst. The mean
  CME speed of Group I is 1022 km/s and that of Group II is 647 km/s. It
  is also found that the properties of the selected M-class flares such
  as flare intensity, rise time, duration and decay time are greater
  for the DH associated flares than the non-DH flares. Group I has a
  slightly larger number (56%) of western events than eastern events
  (44%), whereas Group II has a larger number of eastern events (62%)
  than western events (38%). We also compare this analysis with the
  previous study by Lawrance, Shanmugaraju, and Vršnak (Solar Phys.290,
  3365L, 2015) concerning X-class flares and confirm that high-intensity
  flares (X-class and M-class) have the same trend in the CME and flare
  properties. Additionally we consider aspects like acceleration and the
  possibility of CME-streamer interaction. The average deceleration of
  CMEs with DH type II bursts is weaker (a =−4.39 m/s<SUP>2</SUP>) than
  that of CMEs without a type II burst (a =−12.21 m/s<SUP>2</SUP>). We
  analyze the CME-streamer interactions for Group I events using the
  model proposed by Mancuso and Raymond (Astron. Astrophys.413, 363,
  2004) and find that the interaction regions are the most probable
  source regions for DH type II radio bursts.

---------------------------------------------------------
Title: Validation of the CME Geomagnetic forecast alerts under
    COMESEP alert system
Authors: Dumbovic, Mateja; Srivastava, Nandita; Khodia, Yamini;
   Vršnak, Bojan; Devos, Andy; Rodriguez, Luciano
2017EGUGA..1914917D    Altcode:
  An automated space weather alert system has been developed under the
  EU FP7 project COMESEP (COronal Mass Ejections and Solar Energetic
  Particles: http://comesep.aeronomy.be) to forecast solar energetic
  particles (SEP) and coronal mass ejection (CME) risk levels at
  Earth. COMESEP alert system uses automated detection tool CACTus
  to detect potentially threatening CMEs, drag-based model (DBM)
  to predict their arrival and CME geo-effectiveness tool (CGFT) to
  predict their geomagnetic impact. Whenever CACTus detects a halo or
  partial halo CME and issues an alert, DBM calculates its arrival time
  at Earth and CGFT calculates its geomagnetic risk level. Geomagnetic
  risk level is calculated based on an estimation of the CME arrival
  probability and its likely geo-effectiveness, as well as an estimate
  of the geomagnetic-storm duration. We present the evaluation of the
  CME risk level forecast with COMESEP alert system based on a study
  of geo-effective CMEs observed during 2014. The validation of the
  forecast tool is done by comparing the forecasts with observations. In
  addition, we test the success rate of the automatic forecasts (without
  human intervention) against the forecasts with human intervention using
  advanced versions of DBM and CGFT (self standing tools available at Hvar
  Observatory website: http://oh.geof.unizg.hr). The results implicate
  that the success rate of the forecast is higher with human intervention
  and using more advanced tools. This work has received funding from the
  European Commission FP7 Project COMESEP (263252). We acknowledge the
  support of Croatian Science Foundation under the project 6212 „Solar
  and Stellar Variability".

---------------------------------------------------------
Title: Characteristics of Low-latitude Coronal Holes near the Maximum
    of Solar Cycle 24
Authors: Hofmeister, Stefan J.; Veronig, Astrid; Reiss, Martin A.;
   Temmer, Manuela; Vennerstrom, Susanne; Vršnak, Bojan; Heber, Bernd
2017ApJ...835..268H    Altcode: 2017arXiv170202050H
  We investigate the statistics of 288 low-latitude coronal holes
  extracted from SDO/AIA-193 filtergrams over the time range of
  2011 January 01-2013 December 31. We analyze the distribution of
  characteristic coronal hole properties, such as the areas, mean AIA-193
  intensities, and mean magnetic field densities, the local distribution
  of the SDO/AIA-193 intensity and the magnetic field within the coronal
  holes, and the distribution of magnetic flux tubes in coronal holes. We
  find that the mean magnetic field density of all coronal holes under
  study is 3.0 ± 1.6 G, and the percentaged unbalanced magnetic flux
  is 49 ± 16%. The mean magnetic field density, the mean unsigned
  magnetic field density, and the percentaged unbalanced magnetic flux of
  coronal holes depend strongly pairwise on each other, with correlation
  coefficients cc &gt; 0.92. Furthermore, we find that the unbalanced
  magnetic flux of the coronal holes is predominantly concentrated in
  magnetic flux tubes: 38% (81%) of the unbalanced magnetic flux of
  coronal holes arises from only 1% (10%) of the coronal hole area,
  clustered in magnetic flux tubes with field strengths &gt;50 G (10
  G). The average magnetic field density and the unbalanced magnetic
  flux derived from the magnetic flux tubes correlate with the mean
  magnetic field density and the unbalanced magnetic flux of the overall
  coronal hole (cc &gt; 0.93). These findings give evidence that the
  overall magnetic characteristics of coronal holes are governed by the
  characteristics of the magnetic flux tubes.

---------------------------------------------------------
Title: Understanding the Physical Nature of Coronal "EIT Waves"
Authors: Long, D. M.; Bloomfield, D. S.; Chen, P. F.; Downs, C.;
   Gallagher, P. T.; Kwon, R. -Y.; Vanninathan, K.; Veronig, A. M.;
   Vourlidas, A.; Vršnak, B.; Warmuth, A.; Žic, T.
2017SoPh..292....7L    Altcode: 2016arXiv161105505L
  For almost 20 years the physical nature of globally propagating waves in
  the solar corona (commonly called "EIT waves") has been controversial
  and subject to debate. Additional theories have been proposed over the
  years to explain observations that did not agree with the originally
  proposed fast-mode wave interpretation. However, the incompatibility
  of observations made using the Extreme-ultraviolet Imaging Telescope
  (EIT) onboard the Solar and Heliospheric Observatory with the fast-mode
  wave interpretation was challenged by differing viewpoints from the twin
  Solar Terrestrial Relations Observatory spacecraft and data with higher
  spatial and temporal resolution from the Solar Dynamics Observatory. In
  this article, we reexamine the theories proposed to explain EIT waves
  to identify measurable properties and behaviours that can be compared
  to current and future observations. Most of us conclude that the
  so-called EIT waves are best described as fast-mode large-amplitude
  waves or shocks that are initially driven by the impulsive expansion
  of an erupting coronal mass ejection in the low corona.

---------------------------------------------------------
Title: Solar eruptions: The CME-flare relationship
Authors: Vršnak, B.
2016AN....337.1002V    Altcode:
  Coronal mass ejections (CMEs), caused by large-scale eruptions of the
  coronal magnetic field, often are accompanied by a more localized
  energy release in the form of flares, as a result of dissipative
  magnetic-field reconfiguration. Morphology and evolution of such
  flares, also denoted as dynamical flares are often explained as a
  consequence of reconnection of the arcade magnetic field, taking place
  below the erupting magnetic flux rope. A close relationship of the
  CME acceleration and the flare energy release is evidenced by various
  statistical correlations between parameters describing CMEs and flares,
  as well as by the synchronization of the CME acceleration phase with
  the impulsive phase of the associated flare. Such behavior implies
  that there must be a feedback relation between the dynamics of the CME
  and the flare-associated reconnection process. From the theoretical
  standpoint, magnetic reconnection affects the CME dynamics in several
  ways. First, it reduces the tension of the overlying arcade magnetic
  field and increases the magnetic pressure below the flux rope, and
  in this way enhances the CME acceleration. Furthermore, it supplies
  the poloidal magnetic flux to the flux rope, which helps sustaining
  the electric current in the rope and prolonging the action of the
  driving Lorentz force to large distances. The role of these processes,
  directly relating solar flares and CMEs, is illustrated by employing a
  simple model, where the erupting structure is represented by a curved
  flux rope anchored at both sides in the dense/inert photosphere,
  being subject to the kink and torus instability. It is shown that
  in most strongly accelerated ejections, where values on the order of
  10 km s<SUP>-2</SUP> are attained, the poloidal flux supplied to the
  erupting rope has to be several times larger than was the initial flux.

---------------------------------------------------------
Title: Understanding the Physical Nature of Coronal "EIT Waves"
Authors: Long, D. M.; Bloomfield, D. S.; Chen, P. -F.; Downs,
   C.; Gallagher, P. T.; Kwon, R. -Y.; Vanninathan, K.; Veronig, A.;
   Vourlidas, A.; Vrsnak, B.; Warmuth, A.; Zic, T.
2016usc..confE..24L    Altcode:
  For almost 20 years the physical nature of globally-propagating waves
  in the solar corona (commonly called "EIT waves") has been controversial
  and subject to debate. Additional theories have been proposed throughout
  the years to explain observations that did not fit with the originally
  proposed fast-mode wave interpretation. However, the incompatibility
  of observations made using the Extreme-ultraviolet Imaging Telescope
  (EIT) on the Solar and Heliospheric Observatory with the fast-mode
  wave interpretation have been challenged by differing viewpoints
  from the Solar Terrestrial Relations Observatory spacecraft and higher
  spatial/temporal resolution data from the Solar Dynamics Observatory. In
  this paper, we reexamine the theories proposed to explain "EIT waves"
  to identify measurable properties and behaviours that can be compared
  to current and future observations. Most of us conclude that "EIT
  waves" are best described as fast-mode large-amplitude waves/shocks,
  which are initially driven by the impulsive expansion of an erupting
  coronal mass ejection in the low corona.

---------------------------------------------------------
Title: On the propagation of a geoeffective coronal mass ejection
    during 15-17 March 2015
Authors: Wang, Yuming; Zhang, Quanhao; Liu, Jiajia; Shen, Chenglong;
   Shen, Fang; Yang, Zicai; Zic, T.; Vrsnak, B.; Webb, D. F.; Liu, Rui;
   Wang, S.; Zhang, Jie; Hu, Qiang; Zhuang, Bin
2016JGRA..121.7423W    Altcode: 2016arXiv160707750W
  The largest geomagnetic storm so far, called 2015 St. Patrick's Day
  event, in the solar cycle 24 was produced by a fast coronal mass
  ejection (CME) originating on 15 March 2015. It was an initially
  west-oriented CME and expected to only cause a weak geomagnetic
  disturbance. Why did this CME finally cause such a large geomagnetic
  storm? We try to find some clues by investigating its propagation from
  the Sun to 1 AU. First, we reconstruct the CME's kinematic properties
  in the corona from the SOHO and Solar Dynamics Observatory imaging
  data with the aid of the graduated cylindrical shell model. It is
  suggested that the CME propagated to the west ∼33°±10° away from
  the Sun-Earth line with a speed of about 817 km s<SUP>-1</SUP> before
  leaving the field of view of the SOHO/Large Angle and Spectrometric
  Coronagraph (LASCO) C3 camera. A magnetic cloud (MC) corresponding
  to this CME was measured in situ by the Wind spacecraft 2 days after
  the CME left LASCO's field of view. By applying two MC reconstruction
  methods, we infer the configuration of the MC as well as some kinematic
  information, which implies that the CME possibly experienced an
  eastward deflection on its way to 1 AU. However, due to the lack of
  observations from the STEREO spacecraft, the CME's kinematic evolution
  in interplanetary space is not clear. In order to fill this gap, we
  utilize numerical MHD simulation, drag-based CME propagation model
  (DBM) and the model for CME deflection in interplanetary space (DIPS)
  to recover the propagation process, especially the trajectory, of
  the CME from 30R<SUB>S</SUB> to 1 AU under the constraints of the
  derived CME's kinematics near the Sun and at 1 AU. It is suggested
  that the trajectory of the CME was deflected toward the Earth by
  about 12°, consistent with the implication from the MC reconstruction
  at 1 AU. This eastward deflection probably contributed to the CME's
  unexpected geoeffectiveness by pushing the center of the initially
  west-oriented CME closer to the Earth.

---------------------------------------------------------
Title: VizieR Online Data Catalog: Predicting coronal mass ejections
    transit times (Sudar+, 2016)
Authors: Sudar, D.; Vrsnak, B.; Dumbovic, M.
2016yCat..74561542S    Altcode:
  We compiled a list of 153 CMEs for which their ICME counterparts were
  detected and their TT to Earth was measured. We used only the events
  for which the CME source position could be determined. All CME-ICME
  pairings were taken from the catalogue provided by Richardson &amp;
  Cane (2010, Sol. Phys., 264, 189). <P />(1 data file).

---------------------------------------------------------
Title: Detailed Analysis of Solar Data Related to Historical Extreme
Geomagnetic Storms: 1868 - 2010
Authors: Lefèvre, Laure; Vennerstrøm, Susanne; Dumbović, Mateja;
   Vršnak, Bojan; Sudar, Davor; Arlt, Rainer; Clette, Frédéric;
   Crosby, Norma
2016SoPh..291.1483L    Altcode: 2016SoPh..tmp...64L
  An analysis of historical Sun-Earth connection events in the context
  of the most extreme space weather events of the last ∼150 years
  is presented. To identify the key factors leading to these extreme
  events, a sample of the most important geomagnetic storms was selected
  based mainly on the well-known aa index and on geomagnetic parameters
  described in the accompanying paper (Vennerstrøm et al., Solar Phys. in
  this issue, 2016, hereafter Paper I). This part of the analysis focuses
  on associating and characterizing the active regions (sunspot groups)
  that are most likely linked to these major geomagnetic storms.

---------------------------------------------------------
Title: Extreme Geomagnetic Storms - 1868 - 2010
Authors: Vennerstrom, S.; Lefevre, L.; Dumbović, M.; Crosby, N.;
   Malandraki, O.; Patsou, I.; Clette, F.; Veronig, A.; Vršnak, B.;
   Leer, K.; Moretto, T.
2016SoPh..291.1447V    Altcode: 2016SoPh..tmp...73V
  We present the first large statistical study of extreme geomagnetic
  storms based on historical data from the time period 1868 - 2010. This
  article is the first of two companion papers. Here we describe how the
  storms were selected and focus on their near-Earth characteristics. The
  second article presents our investigation of the corresponding solar
  events and their characteristics. The storms were selected based
  on their intensity in the aa index, which constitutes the longest
  existing continuous series of geomagnetic activity. They are analyzed
  statistically in the context of more well-known geomagnetic indices,
  such as the Kp and Dcx/Dst index. This reveals that neither Kp nor
  Dcx/Dst provide a comprehensive geomagnetic measure of the extreme
  storms. We rank the storms by including long series of single magnetic
  observatory data. The top storms on the rank list are the New York
  Railroad storm occurring in May 1921 and the Quebec storm from March
  1989. We identify key characteristics of the storms by combining
  several different available data sources, lists of storm sudden
  commencements (SSCs) signifying occurrence of interplanetary shocks,
  solar wind in-situ measurements, neutron monitor data, and associated
  identifications of Forbush decreases as well as satellite measurements
  of energetic proton fluxes in the near-Earth space environment. From
  this we find, among other results, that the extreme storms are very
  strongly correlated with the occurrence of interplanetary shocks (91 -
  100 %), Forbush decreases (100 %), and energetic solar proton events
  (70 %). A quantitative comparison of these associations relative to less
  intense storms is also presented. Most notably, we find that most often
  the extreme storms are characterized by a complexity that is associated
  with multiple, often interacting, solar wind disturbances and that they
  frequently occur when the geomagnetic activity is already elevated. We
  also investigate the semiannual variation in storm occurrence and
  confirm previous findings that geomagnetic storms tend to occur less
  frequently near solstices and that this tendency increases with storm
  intensity. However, we find that the semiannual variation depends on
  both the solar wind source and the storm level. Storms associated
  with weak SSC do not show any semiannual variation, in contrast to
  weak storms without SSC.

---------------------------------------------------------
Title: Forbush Decrease Prediction Based on Remote Solar Observations
Authors: Dumbovic, Mateja; Vrsnak, Bojan; Calogovic, Jasa
2016EGUGA..18.6369D    Altcode:
  We study the relation between remote observations of coronal mass
  ejections (CMEs), their associated solar flares and short-term
  depressions in the galactic cosmic-ray flux (so called Forbush
  decreases). Statistical relations between Forbush decrease magnitude
  and several CME/flare parameters are examined. In general we find
  that Forbush decrease magnitude is larger for faster CMEs with larger
  apparent width, which is associated with stronger flares that originate
  close to the center of the solar disk and are (possibly) involved in
  a CME-CME interaction. The statistical relations are quantified and
  employed to forecast expected Forbush decrease magnitude range based
  on the selected remote solar observations of the CME and associated
  solar flare. Several verification measures are used to evaluate
  the forecast method. We find that the forecast is most reliable
  in predicting whether or not a CME will produce a Forbush decrease
  with a magnitude &gt;3 %. The main advantage of the method is that
  it provides an early prediction, 1-4 days in advance. Based on the
  presented research, an online forecast tool was developed (Forbush
  Decrease Forecast Tool, FDFT) available at Hvar Observatory web page:
  http://oh.geof.unizg.hr/FDFT/fdft.php. We acknowledge the support of
  Croatian Science Foundation under the project 6212 "Solar and Stellar
  Variability" and of European social fond under the project "PoKRet".

---------------------------------------------------------
Title: Forecasting the Arrival of Coronal Mass Ejections: The
    Drag-Based Model
Authors: Vršnak, B.; Temmer, M.; Zic, T.; Dumbović, M.; Čalogović,
   J.
2016ASPC..504..209V    Altcode:
  Arrival-time predictions based on the numerical "WSA-ENLIL+Cone model"
  and the analytical "Drag-based model" (DBM) are analyzed, employing
  a sample of 50 well observed CMEs. The best match between the two
  models is obtained if the background solar-wind speed of w = 400 km
  s<SUP>-1</SUP> is applied in DBM. It is also demonstrated that both
  models show similar prediction accuracy.

---------------------------------------------------------
Title: Predicting coronal mass ejections transit times to Earth with
    neural network
Authors: Sudar, D.; Vršnak, B.; Dumbović, M.
2016MNRAS.456.1542S    Altcode: 2015arXiv151107620S
  Predicting transit times (TT) of coronal mass ejections (CMEs) from
  their initial parameters is a very important subject, not only from the
  scientific perspective, but also because CMEs represent a hazard for
  human technology. We used a neural network (NN) to analyse TT for 153
  events with only two input parameters: initial velocity of the CME, v,
  and central meridian distance, CMD, of its associated flare. We found
  that transit time dependence on v is showing a typical drag-like pattern
  in the solar wind. The results show that the speed at which acceleration
  by drag changes to deceleration is v ≈ 500 km s<SUP>-1</SUP>. TT are
  also found to be shorter for CMEs associated with flares on the western
  hemisphere than those originating on the eastern side of the Sun. We
  attribute this difference to the eastward deflection of CMEs on their
  path to 1 AU. The average error of the NN prediction in comparison to
  observations is ≈12 h which is comparable to other studies on the
  same subject.

---------------------------------------------------------
Title: Forbush Decrease Prediction Based on Remote Solar Observations
Authors: Dumbović, M.; Vršnak, B.; Čalogović, J.
2016SoPh..291..285D    Altcode: 2015SoPh..tmp..169D; 2015arXiv151003282D
  We employ remote observations of coronal mass ejections (CMEs)
  and the associated solar flares to forecast the CME-related Forbush
  decreases, i.e. short-term depressions in the galactic cosmic-ray
  flux. The relation between the Forbush effect at Earth and remote
  observations of CMEs and associated solar flares is studied via a
  statistical analysis. Relations between Forbush decrease magnitude and
  several CME/flare parameters were found: the initial CME speed, apparent
  width, source position, associated solar-flare class, and the effect of
  successive-CME occurrence. Based on the statistical analysis, remote
  solar observations are employed to forecast a Forbush-decrease. For
  this purpose, an empirical probabilistic model is constructed that
  uses selected remote solar observations of the CME and associated solar
  flare as input and gives the expected Forbush-decrease magnitude range
  as output. The forecast method is evaluated using several verification
  measures, indicating that as the forecast tends to be more specific, it
  is less reliable, which is its main drawback. However, the advantages
  of the method are that it provides an early prediction and that the
  input does not necessarily depend on using a spacecraft.

---------------------------------------------------------
Title: Formation of Coronal Large-Amplitude Waves and the
    Chromospheric Response
Authors: Vršnak, B.; Žic, T.; Lulić, S.; Temmer, M.; Veronig, A. M.
2016SoPh..291...89V    Altcode: 2015SoPh..tmp..175V
  An in-depth analysis of numerical simulations is performed to obtain
  a deeper insight into the nature of various phenomena occurring in the
  solar atmosphere as a consequence of the eruption of unstable coronal
  structures. Although the simulations take into account only the most
  basic characteristics of a flux-rope eruption, the simulation analysis
  reveals important information on various eruption-related effects. It
  quantifies the relation between the eruption dynamics and the evolution
  of the large-amplitude coronal magnetohydrodynamic wave and the
  associated chromospheric downward-propagating perturbation. We show that
  the downward propagation of the chromospheric Moreton-wave disturbance
  can be approximated by a constant-amplitude switch-on shock that moves
  through a medium of rapidly decreasing Alfvén velocity. The presented
  analysis reveals the nature of secondary effects that are observed
  as coronal upflows, secondary shocks, various forms of wave-trains,
  delayed large-amplitude slow disturbances, transient coronal depletions,
  etc. We also show that the eruption can cause an observable Moreton
  wave and a secondary coronal front only if it is powerful enough and
  is preferably characterized by significant lateral expansion. In weaker
  eruptions, only the coronal and transition-region signatures of primary
  waves are expected to be observed. In powerful events, the primary
  wave moves at an Alfvén Mach number significantly larger than 1 and
  steepens into a shock that is due to the nonlinear evolution of the
  wavefront. After the eruption-driven phase, the perturbation evolves
  as a freely propagating simple wave, characterized by a significant
  deceleration, amplitude decrease, and wave-profile broadening. In weak
  events the coronal wave does not develop into a shock and propagates
  at a speed close to the ambient magnetosonic speed.

---------------------------------------------------------
Title: Flare-CME Models: An Observational Perspective (Invited Review)
Authors: Schmieder, B.; Aulanier, G.; Vršnak, B.
2015SoPh..290.3457S    Altcode: 2015SoPh..tmp...64S
  Eruptions, flares, and coronal mass ejection (CMEs) are due to physical
  phenomena mainly driven by an initially force-free current-carrying
  magnetic field. We review some key observations relevant to the
  current theoretical trigger mechanisms of the eruption and to the
  energy release via reconnection. Sigmoids observed in X-rays and UV,
  as well as the pattern (double J-shaped) of electric currents in
  the photosphere show clear evidence of the existence of currents
  parallel to the magnetic field and can be the signature of a flux
  rope that is detectable in CMEs. The magnetic helicity of filaments
  and active regions is an interesting indirectly measurable parameter
  because it can quantify the twist of the flux rope. On the other hand,
  the magnetic helicity of the solar structures allows us to associate
  solar eruptions and magnetic clouds in the heliosphere. The magnetic
  topology analysis based on the 3D magnetic field extrapolated from
  vector magnetograms is a good tool for identifying the reconnection
  locations (null points and/or the 3D large volumes - hyperbolic flux
  tube, HFT). Flares are associated more with quasi-separatrix layers
  (QSLs) and HFTs than with a single null point, which is a relatively
  rare case. We review various mechanisms that have been proposed to
  trigger CMEs and their observable signatures: by "breaking" the field
  lines overlying the flux rope or by reconnection below the flux rope
  to reduce the magnetic tension, or by letting the flux rope to expand
  until it reaches a minimum threshold height (loss of equilibrium or
  torus instability). Additional mechanisms are commonly operating in
  the solar atmosphere. Examples of observations are presented throughout
  the article and are discussed in this framework.

---------------------------------------------------------
Title: Investigation of X-class Flare-Associated Coronal Mass
    Ejections with and without DH Type II Radio Bursts
Authors: Lawrance, M. Bendict; Shanmugaraju, A.; Vršnak, Bojan
2015SoPh..290.3365L    Altcode: 2015SoPh..tmp..163L
  A statistical analysis of 135 out of 141 X-class flares observed during
  1997 - 2012 with and without deca-hectometric (DH) type II radio bursts
  has been performed. It was found that 79 events (X-class flares and
  coronal mass ejections - Group I) were associated with DH type II radio
  bursts and 62 X-class flare events were not. Out of these 62 events
  without DH type IIs, 56 events (Group II) have location information,
  and they were selected for this study. Of these 56 events, only 32
  were associated with CMEs. Most of the DH-associated X-class events
  (∼79 % ) were halo CMEs, in contrast to 14 % in Group II. The
  average CME speed of the X-class flares associated with DH type IIs
  is 1555 km s<SUP>−1</SUP>, which is nearly twice that of the X-class
  flare-associated CMEs without DH event (744 km s<SUP>−1</SUP>). The
  X-class flares associated with DH radio bursts have a mean flare
  intensity (3.63 ×10<SUP>−4</SUP>Wm−<SUP>2</SUP>) that is 38 %
  greater than that of X-class flares without DH radio bursts (2.23
  ×10<SUP>−4</SUP>Wm−<SUP>2</SUP>). In addition to the greater
  intensity, it is also found that the the duration and rise time of
  flares associated with DH radio emission (DH flares) is more than
  twice than that of the flares without DH radio emission. When the
  events were further divided into two categories with respect to their
  source locations in eastern and western regions, 65 % of the events
  in the radio-loud category (with DH radio bursts) are from the western
  hemisphere and the remaining 35 % are from the eastern hemisphere. On
  the other hand, in the radio-quiet category (without DH radio bursts),
  nearly 60 % of the events are from the eastern hemisphere in contrast to
  those of the radio-loud category. It is found that 81 % of the events
  from eastern regions have flare durations &gt; 30 min in the DH-flare
  category, in contrast to a nearly equal number from the western side
  for flare durations longer/shorter than 30 min. Similarly, the eastern
  events in the DH-flare category have a longer average rise-time of
  34 min, while the western events have an average flare rise-time of
  26 min. On the other hand, the CME speed and flare strength are found
  to be nearly equal among east and west side events, except that both
  these parameters are greater for events with DH type IIs.

---------------------------------------------------------
Title: Division II: Commission 10: Solar Activity
Authors: van Driel-Gesztelyi, Lidia; Scrijver, Karel J.; Klimchuk,
   James A.; Charbonneau, Paul; Fletcher, Lyndsay; Hasan, S. Sirajul;
   Hudson, Hugh S.; Kusano, Kanya; Mandrini, Cristina H.; Peter, Hardi;
   Vršnak, Bojan; Yan, Yihua
2015IAUTB..28..106V    Altcode:
  The Business Meeting of Commission 10 was held as part of the Business
  Meeting of Division II (Sun and Heliosphere), chaired by Valentin
  Martínez-Pillet, the President of the Division. The President of
  Commission 10 (C10; Solar activity), Lidia van Driel-Gesztelyi, took
  the chair for the business meeting of C10. She summarised the activities
  of C10 over the triennium and the election of the incoming OC.

---------------------------------------------------------
Title: Heliospheric Propagation of Coronal Mass Ejections: Drag-based
    Model Fitting
Authors: Žic, T.; Vršnak, B.; Temmer, M.
2015ApJS..218...32Z    Altcode: 2015arXiv150608582Z
  The so-called drag-based model (DBM) simulates analytically the
  propagation of coronal mass ejections (CMEs) in interplanetary space
  and allows the prediction of their arrival times and impact speeds at
  any point in the heliosphere (“target”). The DBM is based on the
  assumption that beyond a distance of about 20 solar radii from the
  Sun, the dominant force acting on CMEs is the “aerodynamic” drag
  force. In the standard form of DBM, the user provisionally chooses
  values for the model input parameters, by which the kinematics of the
  CME over the entire Sun-“target” distance range is defined. The
  choice of model input parameters is usually based on several previously
  undertaken statistical studies. In other words, the model is used
  by ad hoc implementation of statistics-based values of the input
  parameters, which are not necessarily appropriate for the CME under
  study. Furthermore, such a procedure lacks quantitative information
  on how well the simulation reproduces the coronagraphically observed
  kinematics of the CME, and thus does not provide an estimate of the
  reliability of the arrival prediction. In this paper we advance the DBM
  by adopting it in a form that employs the CME observations over a given
  distance range to evaluate the most suitable model input parameters
  for a given CME by means of least-squares fitting. Furthermore, the
  new version of the model automatically responds to any significant
  change of the conditions in the ambient medium (solar wind speed,
  density, CME-CME interactions, etc.) by changing the model input
  parameters according to changes in the CME kinematics. The advanced
  DBM is shaped in a form that can be readily employed in an operational
  system for real-time space-weather forecasting by promptly adjusting
  to a successively expanding observational data set, thus providing a
  successively improving prediction of the CME arrival.

---------------------------------------------------------
Title: Strong coronal channelling and interplanetary evolution of
    a solar storm up to Earth and Mars
Authors: Möstl, Christian; Rollett, Tanja; Frahm, Rudy A.; Liu,
   Ying D.; Long, David M.; Colaninno, Robin C.; Reiss, Martin A.;
   Temmer, Manuela; Farrugia, Charles J.; Posner, Arik; Dumbović,
   Mateja; Janvier, Miho; Démoulin, Pascal; Boakes, Peter; Devos, Andy;
   Kraaikamp, Emil; Mays, Mona L.; Vršnak, Bojan
2015NatCo...6.7135M    Altcode: 2015arXiv150602842M; 2015NatCo...6E7135M
  The severe geomagnetic effects of solar storms or coronal mass
  ejections (CMEs) are to a large degree determined by their propagation
  direction with respect to Earth. There is a lack of understanding of
  the processes that determine their non-radial propagation. Here we
  present a synthesis of data from seven different space missions of a
  fast CME, which originated in an active region near the disk centre
  and, hence, a significant geomagnetic impact was forecasted. However,
  the CME is demonstrated to be channelled during eruption into a
  direction +37+/-10° (longitude) away from its source region, leading
  only to minimal geomagnetic effects. In situ observations near Earth
  and Mars confirm the channelled CME motion, and are consistent with
  an ellipse shape of the CME-driven shock provided by the new Ellipse
  Evolution model, presented here. The results enhance our understanding
  of CME propagation and shape, which can help to improve space weather
  forecasts.

---------------------------------------------------------
Title: Real-Time Solar Wind Prediction Based on SDO/AIA Coronal
    Hole Data
Authors: Rotter, T.; Veronig, A. M.; Temmer, M.; Vršnak, B.
2015SoPh..290.1355R    Altcode: 2015arXiv150106697R; 2015SoPh..tmp...37R
  We present an empirical model based on the visible area covered by
  coronal holes close to the central meridian with the aim to predict
  the solar wind speed at 1 AU with a lead time of up to four days in
  advance with a time resolution of one hour. Linear prediction functions
  are used to relate coronal hole areas to solar wind speed. The function
  parameters are automatically adapted by using the information from the
  previous three Carrington Rotations. Thus the algorithm automatically
  reacts to the changes of the solar wind speed during different phases
  of the solar cycle. The adaptive algorithm was applied to and tested
  on SDO/AIA-193 Å observations and ACE measurements during the years
  2011 - 2013, covering 41 Carrington Rotations. The solar wind needs
  on average 4.02±0.5 days to reach Earth. The algorithm produces good
  predictions for the 156 solar wind high-speed streams peak amplitudes
  with correlation coefficients of cc≈0.60. For 80 % of the peaks,
  the predicted arrival matches the ACE in situ measurements within a
  time window of 0.5 days. The same algorithm, using linear predictions,
  was also applied to predict the magnetic field strength in wind streams
  originating from coronal hole areas, but it did not give reliable
  predictions (cc≈0.15).

---------------------------------------------------------
Title: Strong coronal deflection of a CME and its interplanetary
    evolution to Earth and Mars
Authors: Möstl, Christian; Rollett, Tanja; Frahm, Rudy A.; Liu, Ying
   D.; Long, David M.; Colaninno, Robin C.; Reiss, Martin A.; Temmer,
   Manuela; Farrugia, Charles J.; Posner, Arik; Dumbovic, Mateja; Janvier,
   Miho; Demoulin, Pascal; Boakes, Peter; Devos, Andy; Kraaikamp, Emil;
   Mays, Mona L.; Vrsnak, Bojan
2015EGUGA..17.1366M    Altcode:
  We discuss multipoint imaging and in situ observations of the coronal
  mass ejection (CME) on January 7 2014 which resulted in a major false
  alarm. While the source region was almost at disk center facing Earth,
  the eruption was strongly deflected in the corona, and in conjunction
  with its particular orientation this CME missed Earth almost entirely,
  leading to no significant geomagnetic effects. We demonstrate this
  by a synthesis of data from 7 different heliospheric and planetary
  space missions (STEREO-A/B, SOHO, SDO, Wind, Mars Express, Mars
  Science Laboratory). The CMEs ecliptic part was deflected by 37
  ± 10° in heliospheric longitude, a value larger than previously
  thought. Multipoint in situ observations at Earth and Mars confirm
  the deflection, and are consistent with an elliptical interplanetary
  shock shape of aspect ratio 1.4 ± 0.4. We also discuss our new method,
  the Ellipse Evolution (ElEvo) model, which allows us to optimize the
  global shape of the CME shock with multipoint in situ observations of
  the interplanetary CME arrival. ElEvo, which is an extension to the
  Drag-Based-Model by Vrsnak et al., may also be used for real time space
  weather forecasting. The presented results enhance our understanding
  of CME deflection and shape, which are fundamental ingredients for
  improving space weather forecasts.

---------------------------------------------------------
Title: Geoeffectiveness of Coronal Mass Ejections in the SOHO Era
Authors: Dumbović, M.; Devos, A.; Vršnak, B.; Sudar, D.; Rodriguez,
   L.; Ruždjak, D.; Leer, K.; Vennerstrøm, S.; Veronig, A.
2015SoPh..290..579D    Altcode: 2014arXiv1410.3303D
  The main objective of the study is to determine the probability
  distributions of the geomagnetic Dst index as a function of the
  coronal mass ejection (CME) and solar flare parameters for the purpose
  of establishing a probabilistic forecast tool for the intensity of
  geomagnetic storms. We examined several CME and flare parameters as well
  as the effect of successive CME occurrence in changing the probability
  for a certain range of Dst index values. The results confirm some
  previously known relationships between remotely observed properties of
  solar eruptive events and geomagnetic storms: the importance of the
  initial CME speed, apparent width, source position, and the class of
  the associated solar flare. We quantify these relationships in a form
  that can be used for future space-weather forecasting. The results of
  the statistical study are employed to construct an empirical statistical
  model for predicting the probability of the geomagnetic storm intensity
  based on remote solar observations of CMEs and flares.

---------------------------------------------------------
Title: Initiation and Evolution of Global Coronal Waves
Authors: Vršnak, B.; Muhr, N.; Žic, T.; Lulić, S.; Kienreich,
   I. W.; Temmer, M.; Veronig, A. M.
2015CEAB...39...65V    Altcode:
  Some essential outcomes of a detailed analysis of the formation and
  evolution of the coronal EUV wave of 15 February 2011 are presented,
  focused on the relationship between the source region expansion, wave
  kinematics, and the evolution of the wave amplitude. The observations
  are explained in terms of the results of the numerical MHD simulations,
  providing new insights into the physical background of coronal waves,
  especially considering the nature of the relationship of the wave
  amplitude and propagation velocity in different phases of the wave
  evolution.

---------------------------------------------------------
Title: Forbush decreases associated to Stealth Coronal Mass Ejections
Authors: Heber, B.; Wallmann, C.; Galsdorf, D.; Herbst K.; Kühl,
   P.; Dumbovic, M.; Vršnak, B.; Veronig, A.; Temmer, M.; Möstl, C.;
   Dalla, S.
2015CEAB...39...75H    Altcode:
  Interplanetary coronal mass ejections (ICMEs) are structures in the
  solar wind that are the counterparts of coronal mass ejections (CMEs)
  at the Sun. It is commonly believed that enhanced magnetic fields
  in interplanetary shocks and solar ejecta as well as the increased
  turbulence in the solar wind sheath region are the cause of Forbush
  decreases (FDs) representing decreases of galactic cosmic ray (GCR)
  intensities. Recently, stealth CMEs i.e.~CMEs with no apparent solar
  surface association have become a subject in recent studies of solar
  activity. Whether all of such stealth CMEs can drive a FD is difficult
  to investigate on the basis of neutron monitor NM measurements because
  these measurements not only reflect the GCR intensity variation in
  interplanetary space but also the variation of the geomagnetic field as
  well as the conditions in the Earth atmosphere. Single detector counter
  from spacecraft instrumentation, here SOHO and Chandra EPHIN, exceed
  counting statistic of NMs allowing to determine intensity variation of
  less than 1 permil in interplanetary space on the basis of 30 minute
  count rate averages. Here we present the ongoing analysis of eleven
  stealth CMEs.

---------------------------------------------------------
Title: Statistical Analysis of Large-Scale EUV Waves Observed by
    STEREO/EUVI
Authors: Muhr, N.; Veronig, A. M.; Kienreich, I. W.; Vršnak, B.;
   Temmer, M.; Bein, B. M.
2014SoPh..289.4563M    Altcode: 2014arXiv1408.2513M; 2014SoPh..tmp..126M
  We statistically analyzed the kinematical evolution and wave pulse
  characteristics of 60 strong large-scale EUV wave events that
  occurred during January 2007 to February 2011 with the STEREO
  twin spacecraft. For the start velocity, the arithmetic mean
  is 312±115 km s<SUP>−1</SUP> (within a range of 100 - 630 km
  s<SUP>−1</SUP>). For the mean (linear) velocity, the arithmetic
  mean is 254±76 km s<SUP>−1</SUP> (within a range of 130 - 470
  km s<SUP>−1</SUP>). 52 % of all waves under study show a distinct
  deceleration during their propagation (a≤−50 m s<SUP>−2</SUP>),
  the other 48 % are consistent with a constant speed within the
  uncertainties (−50≤a≤50 m s<SUP>−2</SUP>). The start velocity
  and the acceleration are strongly anticorrelated with c≈−0.8,
  i.e. initially faster events undergo stronger deceleration than
  slower events. The (smooth) transition between constant propagation
  for slow events and deceleration in faster events occurs at an EUV wave
  start-velocity of v≈230 km s<SUP>−1</SUP>, which corresponds well to
  the fast-mode speed in the quiet corona. These findings provide strong
  evidence that the EUV waves under study are indeed large-amplitude
  fast-mode MHD waves. This interpretation is also supported by the
  correlations obtained between the peak velocity and the peak amplitude,
  impulsiveness, and build-up time of the disturbance. We obtained
  the following association rates of EUV wave events with other solar
  phenomena: 95 % are associated with a coronal mass ejection (CME),
  74 % to a solar flare, 15 % to interplanetary type II bursts, and 22
  % to coronal type II bursts. These findings are consistent with the
  interpretation that the associated CMEs are the driving agents of the
  EUV waves.

---------------------------------------------------------
Title: Interaction Between Two CMEs During 14 - 15 February 2011
    and Their Unusual Radio Signature
Authors: Shanmugaraju, A.; Prasanna Subramanian, S.; Vrsnak, Bojan;
   Ibrahim, M. Syed
2014SoPh..289.4621S    Altcode: 2014SoPh..tmp..125S
  We report a detailed analysis of an interaction between two coronal
  mass ejections (CMEs) that were observed on 14 - 15 February 2011
  and the corresponding radio enhancement, which was similar to the
  "CME cannibalism" reported by Gopalswamy et al. (Astrophys. J.548,
  L91, 2001). A primary CME, with a mean field-of-view velocity of 669 km
  s<SUP>−1</SUP> in the Solar and Heliospheric Observatory (SOHO)/Large
  Angle Spectrometric Coronagraph (LASCO), was more than as twice as
  fast as the slow CME preceding it (326 km s<SUP>−1</SUP>), which
  indicates that the two CMEs interacted. A radio-enhancement signature
  (in the frequency range 1 MHz - 400 kHz) due to the CME interaction
  was analyzed and interpreted using the CME data from LASCO and from
  the Solar Terrestrial Relations Observatory (STEREO) HI-1, radio data
  from Wind/Radio and Plasma Wave Experiment (WAVES), and employing known
  electron-density models and kinematic modeling. The following results
  are obtained: i) The CME interaction occurred around 05:00 - 10:00 UT
  in a height range 20 - 25 R<SUB>⊙</SUB>. An unusual radio signature
  is observed during the time of interaction in the Wind/WAVES dynamic
  radio spectrum. ii) The enhancement duration shows that the interaction
  segment might be wider than 5 R<SUB>⊙</SUB>. iii) The shock height
  estimated using density models for the radio enhancement region is
  10 - 30 R<SUB>⊙</SUB>. iv) Using kinematic modeling and assuming a
  completely inelastic collision, the decrease of kinetic energy based on
  speeds from LASCO data is determined to be 0.77×10<SUP>23</SUP> J, and
  3.67×10<SUP>23</SUP> J if speeds from STEREO data are considered. vi)
  The acceleration, momentum, and force are found to be a=−168 m
  s<SUP>−2</SUP>, I=6.1×10<SUP>18</SUP> kg m s<SUP>−1</SUP>, and
  F=1.7×10<SUP>15</SUP> N, respectively, using STEREO data.

---------------------------------------------------------
Title: Heliospheric Propagation of Coronal Mass Ejections: Comparison
    of Numerical WSA-ENLIL+Cone Model and Analytical Drag-based Model
Authors: Vršnak, B.; Temmer, M.; Žic, T.; Taktakishvili, A.;
   Dumbović, M.; Möstl, C.; Veronig, A. M.; Mays, M. L.; Odstrčil, D.
2014ApJS..213...21V    Altcode:
  Real-time forecasting of the arrival of coronal mass ejections (CMEs) at
  Earth, based on remote solar observations, is one of the central issues
  of space-weather research. In this paper, we compare arrival-time
  predictions calculated applying the numerical "WSA-ENLIL+Cone
  model" and the analytical "drag-based model" (DBM). Both models use
  coronagraphic observations of CMEs as input data, thus providing an
  early space-weather forecast two to four days before the arrival of
  the disturbance at the Earth, depending on the CME speed. It is shown
  that both methods give very similar results if the drag parameter Γ =
  0.1 is used in DBM in combination with a background solar-wind speed
  of w = 400 km s<SUP>-1</SUP>. For this combination, the mean value
  of the difference between arrival times calculated by ENLIL and DBM
  is \overline{Δ }=0.09+/- 9.0 hr with an average of the absolute-value
  differences of \overline{\vert Δ \vert }=7.1 hr. Comparing the observed
  arrivals (O) with the calculated ones (C) for ENLIL gives O - C = -0.3
  ± 16.9 hr and, analogously, O - C = +1.1 ± 19.1 hr for DBM. Applying
  Γ = 0.2 with w = 450 km s<SUP>-1</SUP> in DBM, one finds O - C =
  -1.7 ± 18.3 hr, with an average of the absolute-value differences
  of 14.8 hr, which is similar to that for ENLIL, 14.1 hr. Finally,
  we demonstrate that the prediction accuracy significantly degrades
  with increasing solar activity.

---------------------------------------------------------
Title: Combined Multipoint Remote and in situ Observations of the
    Asymmetric Evolution of a Fast Solar Coronal Mass Ejection
Authors: Rollett, T.; Möstl, C.; Temmer, M.; Frahm, R. A.; Davies,
   J. A.; Veronig, A. M.; Vršnak, B.; Amerstorfer, U. V.; Farrugia,
   C. J.; Žic, T.; Zhang, T. L.
2014ApJ...790L...6R    Altcode: 2014arXiv1407.4687R
  We present an analysis of the fast coronal mass ejection (CME) of 2012
  March 7, which was imaged by both STEREO spacecraft and observed in
  situ by MESSENGER, Venus Express, Wind, and Mars Express. Based on
  detected arrivals at four different positions in interplanetary space,
  it was possible to strongly constrain the kinematics and the shape of
  the ejection. Using the white-light heliospheric imagery from STEREO-A
  and B, we derived two different kinematical profiles for the CME
  by applying the novel constrained self-similar expansion method. In
  addition, we used a drag-based model to investigate the influence of
  the ambient solar wind on the CME's propagation. We found that two
  preceding CMEs heading in different directions disturbed the overall
  shape of the CME and influenced its propagation behavior. While the
  Venus-directed segment underwent a gradual deceleration (from ~2700 km
  s<SUP>-1</SUP> at 15 R <SUB>⊙</SUB> to ~1500 km s<SUP>-1</SUP> at 154
  R <SUB>⊙</SUB>), the Earth-directed part showed an abrupt retardation
  below 35 R <SUB>⊙</SUB> (from ~1700 to ~900 km s<SUP>-1</SUP>). After
  that, it was propagating with a quasi-constant speed in the wake of
  a preceding event. Our results highlight the importance of studies
  concerning the unequal evolution of CMEs. Forecasting can only be
  improved if conditions in the solar wind are properly taken into
  account and if attention is also paid to large events preceding the
  one being studied.

---------------------------------------------------------
Title: Shock ahead ICMEs analyzed from in situ data
Authors: Maricic, D.; Rosa, D.; Karlica, M.; Dumbovic, M.; Vrsnak,
   B.; Hrzina, D.; Romstajn, I.
2014simi.conf....7M    Altcode:
  We analyzed solar wind disturbances recorded by WIND satellite
  which can be connected with corresponding ICMEs recorded in Solar
  Terrestrial Relations Observatory (STEREO) data, in the period from
  2008 to 2013. Detailed analysis of the in situ data reveals complex and
  different internal structures of the disturbances, where signatures
  of the initially independent ICMEs could be recognized. Separating
  the disturbances in different types, we focus on the disturbances
  in which we can analyze shock ahead the ICMEs. Correlations of the
  magnetic field strength, solar-wind speed, proton density and thermal
  velocity are presented. Finally, we employ the ground-based cosmic
  ray observations and Dst index, to investigate the connection between
  CME manifestations with the Forbush decrease (FD) and its influence
  on the Earth's magnetic field. The results presented provide a better
  understanding of the ICME morphology and reveal effects that should
  be taken into account in forecasting of the arrival of such compound
  structures.

---------------------------------------------------------
Title: Connecting Speeds, Directions and Arrival Times of 22 Coronal
    Mass Ejections from the Sun to 1 AU
Authors: Möstl, C.; Amla, K.; Hall, J. R.; Liewer, P. C.; De Jong,
   E. M.; Colaninno, R. C.; Veronig, A. M.; Rollett, T.; Temmer, M.;
   Peinhart, V.; Davies, J. A.; Lugaz, N.; Liu, Y. D.; Farrugia, C. J.;
   Luhmann, J. G.; Vršnak, B.; Harrison, R. A.; Galvin, A. B.
2014ApJ...787..119M    Altcode: 2014arXiv1404.3579M
  Forecasting the in situ properties of coronal mass ejections (CMEs)
  from remote images is expected to strongly enhance predictions of
  space weather and is of general interest for studying the interaction
  of CMEs with planetary environments. We study the feasibility of using
  a single heliospheric imager (HI) instrument, imaging the solar wind
  density from the Sun to 1 AU, for connecting remote images to in situ
  observations of CMEs. We compare the predictions of speed and arrival
  time for 22 CMEs (in 2008-2012) to the corresponding interplanetary
  coronal mass ejection (ICME) parameters at in situ observatories
  (STEREO PLASTIC/IMPACT, Wind SWE/MFI). The list consists of front-
  and backsided, slow and fast CMEs (up to 2700 km s<SUP>-1</SUP>). We
  track the CMEs to 34.9 ± 7.1 deg elongation from the Sun with J maps
  constructed using the SATPLOT tool, resulting in prediction lead times
  of -26.4 ± 15.3 hr. The geometrical models we use assume different
  CME front shapes (fixed-Φ, harmonic mean, self-similar expansion) and
  constant CME speed and direction. We find no significant superiority
  in the predictive capability of any of the three methods. The absolute
  difference between predicted and observed ICME arrival times is 8.1 ±
  6.3 hr (rms value of 10.9 hr). Speeds are consistent to within 284 ±
  288 km s<SUP>-1</SUP>. Empirical corrections to the predictions enhance
  their performance for the arrival times to 6.1 ± 5.0 hr (rms value
  of 7.9 hr), and for the speeds to 53 ± 50 km s<SUP>-1</SUP>. These
  results are important for Solar Orbiter and a space weather mission
  positioned away from the Sun-Earth line.

---------------------------------------------------------
Title: Morphology of an ICME-event derived by Multi-point in Situ
    and Heliospheric Imaging Data
Authors: Rollett, Tanja; Möstl, Christian; Temmer, Manuela; Veronig,
   Astrid M.; Frahm, Rudy A.; Davies, Jackie A.; Vrsnak, Bojan; Farrugia,
   Charles J.; Amerstorfer, Ute V.
2014EGUGA..1610892R    Altcode:
  We show the analysis of an outstanding fast interplanetary coronal
  mass ejection (ICME) of 07 March 2012, which has been observed
  stereoscopically from both STEREO spacecraft. Assuming self-similar
  expansion and constant direction of motion we derive the kinematical
  profiles for the eastern and the western part of the roughly
  Earth-directed ICME. As additional constraints we use the huge
  advantage of in situ measurements at various locations during the
  ICME's propagation, namely from Venus Express, Messenger, Wind and
  Mars Express. We found that the eastern part of the ICME had a much
  higher propagation speed than its western part. Using the drag-based
  model, a model for the propagation of ICMEs in the inner heliosphere,
  we analyzed the influence of the drag on both sides of the ICME due
  to the surrounding solar wind conditions. These different solar wind
  conditions could have been the reason for the differing velocities
  and therefore for a distortion of the ICME front. These studies are
  fundamental in order to deepen the understanding of ICME evolution
  and to enhance existing forecasting methods.

---------------------------------------------------------
Title: Connecting speeds, directions and arrival times of 22 coronal
    mass ejections from the Sun to 1 AU
Authors: Möstl, Christian; Amla, Keshav; Hall, Jeff R.; Liewer,
   Paulett C.; DeJong, Eric M.; Colaninno, Robin C.; Veronig, Astrid M.;
   Rollett, Tanja; Temmer, Manuela; Peinhart, Vanessa; Davies, Jackie
   A.; Lugaz, Noé; Liu, Ying; Farrugia, Charles J.; Luhmann, Janet G.;
   Vrsnak, Bojan; Harrison, Richard A.; Galvin, Antoinette B.
2014EGUGA..16.1755M    Altcode:
  Forecasting in situ properties of coronal mass ejections (CMEs) from
  remote images is expected to strongly enhance predictions of space
  weather, and is of general interest for studying the interaction of
  the solar wind with planetary environments. We study the feasibility of
  using a heliospheric imager (HI) instrument, which is able to image the
  solar wind density along the full Sun to 1 AU distance, for connecting
  remote images to in situ observations of CMEs. Such an instrument
  is currently in operation on each of the two STEREO spacecraft. We
  compare the predictions for speed and arrival time for 22 different
  CME events (between 2008-2012), each observed remotely by one STEREO
  spacecraft, to the interplanetary coronal mass ejection (ICME) speed and
  arrival time observed at in situ observatories (STEREO PLASTIC/IMPACT,
  Wind SWE/MFI). We use croissant modeling for STEREO/COR2, and with a
  single-spacecraft STEREO/HI instrument, we track each CME to 34.9 ± 7.1
  degree elongation from the Sun with J-maps constructed with the SATPLOT
  tool. We then fit geometrical models to each track, assuming different
  CME front shapes (Fixed-Φ, Harmonic Mean, Self-Similar Expansion),
  and constant CME speed and direction. We find no significant preference
  in the predictive capability for any of the three geometrical modeling
  methods used on the full event list, consisting of front- and backsided,
  slow and fast CMEs (up to 2700 km s-1). The absolute difference between
  predicted and observed ICME arrival times is 8.1 ± 6.4 hours (rms
  value of 10.9h), and speeds are consistent within 284 ± 291 km s-1,
  including the geometric effects of CME apex or flank encounters. We
  derive new empirical corrections to the imaging results, enhancing
  the performance of the arrival time predictions to 6.1 ± 5.0 hours
  (rms value of 7.9h), and the speed predictions to 53 ± 50 km s-1,
  for this particular set of events. The prediction lead time is around
  1 day (-26.4 ± 15.3h). CME directions given by the HI methods differ
  considerably, and biases are found on the order of 30-50 degree in
  heliospheric longitude, consistent with theoretical expectations. These
  results are of interest concerning future missions such as Solar Orbiter
  or a dedicated space weather mission positioned remotely from the Earth.

---------------------------------------------------------
Title: Asymmetry in the CME-CME Interaction Process for the Events
    from 2011 February 14-15
Authors: Temmer, M.; Veronig, A. M.; Peinhart, V.; Vršnak, B.
2014ApJ...785...85T    Altcode: 2014arXiv1402.6891T
  We present a detailed study of the interaction process of two coronal
  mass ejections (CMEs) successively launched on 2011 February 14 (CME1)
  and 2011 February 15 (CME2). Reconstructing the three-dimensional
  shape and evolution of the flux ropes, we verify that the two CMEs
  interact. The frontal structure of both CMEs, measured along different
  position angles (PAs) over the entire latitudinal extent, reveals
  differences in the kinematics for the interacting flanks and the
  apexes. The interaction process is strongly PA-dependent in terms of
  timing as well as kinematical evolution. The central interaction occurs
  along PA-100°, which shows the strongest changes in kinematics. During
  interaction, CME1 accelerates from ~400 km s<SUP>-1</SUP> to ~700 km
  s<SUP>-1</SUP> and CME2 decelerates from ~1300 km s<SUP>-1</SUP> to ~600
  km s<SUP>-1</SUP>. Our results indicate that a simplified scenario such
  as inelastic collision may not be sufficient to describe the CME-CME
  interaction. The magnetic field structures of the intertwining flux
  ropes and the momentum transfer due to shocks each play an important
  role in the interaction process.

---------------------------------------------------------
Title: Investigation of the Coronal Magnetic Field Using a Type II
    Solar Radio Burst
Authors: Vasanth, V.; Umapathy, S.; Vršnak, Bojan; Žic, Tomislav;
   Prakash, O.
2014SoPh..289..251V    Altcode: 2013arXiv1305.1760V
  The type II solar radio burst recorded on 13 June 2010 by the Hiraiso
  Solar Observatory Radio Spectrograph was employed to estimate
  the magnetic-field strength in the solar corona. The burst was
  characterized by a well-pronounced band splitting, which we used to
  estimate the density jump at the shock and Alfvén Mach number using the
  Rankine-Hugoniot relation. We convert the plasma frequency of the type
  II burst into height [R] in solar radii using an appropriate density
  model, and then we estimated the shock speed [V<SUB>s</SUB>], coronal
  Alfvén velocity [V<SUB>A</SUB>], and the magnetic-field strength at
  different heights. The relative bandwidth of the band splitting was
  found to be in the range 0.2 - 0.25, corresponding to a density jump
  of X=1.44 - 1.56, and an Alfvén Mach number of M<SUB>A</SUB>=1.35 -
  1.45. The inferred mean shock speed was on the order of V≈667 km
  s<SUP>−1</SUP>. From the dependencies V(R) and M<SUB>A</SUB>(R)
  we found that the Alfvén speed slightly decreases at R≈1.3 - 1.5
  R<SUB>⊙</SUB>. The magnetic-field strength decreases from a value
  between 2.7 and 1.7 G at R≈1.3 - 1.5 R<SUB>⊙</SUB>, depending on
  the coronal-density model employed. Our results are in good agreement
  with the empirical scaling by Dulk and McLean (Solar Phys. 57, 279,
  1978) and Gopalswamy et al. (Astrophys. J.744, 72, 2012). Our results
  show that the type II band-splitting method is an important tool for
  inferring the coronal magnetic field, especially when independent
  measurements are made from white-light observations.

---------------------------------------------------------
Title: Transit Time of Coronal Mass Ejections under Different Ambient
    Solar Wind Conditions
Authors: Shanmugaraju, A.; Vršnak, Bojan
2014SoPh..289..339S    Altcode:
  The speed [v(R)] of coronal mass ejections (CMEs) at various distances
  from the Sun is modeled (as proposed by Vršnak and Gopalswamy in
  J. Geophys. Res. 107, 2002, doi:10.1029/2001/JA000120) by using the
  equation of motion a<SUB>drag</SUB>=γ(v−w) and its quadratic form
  a<SUB>drag</SUB>=γ(v−w)|v−w|, where v and w are the speeds of
  the CME and solar wind, respectively. We assume that the parameter γ
  can be expressed as γ=αR<SUP>β</SUP>, where R is the heliocentric
  distance, and α and β are constants. We extend the analysis of
  Vršnak and Gopalswamy to obtain a more detailed insight into the
  dependence of the CME Sun-Earth transit time on the CME speed and the
  ambient solar-wind speed, for different combinations of α and β. In
  such a parameter-space analysis, the results obtained confirm that
  the CME transit time depends strongly on the state of the ambient
  solar wind. Specifically, we found that: i) for a particular set
  of values of α and β, a difference in the solar-wind speed causes
  larger transit-time differences at low CME speeds [v<SUB>0</SUB>],
  than at high v<SUB>0</SUB>; ii) the difference between transit times of
  slow and fast CMEs is larger at low solar-wind speed [w<SUB>0</SUB>]
  than at high w<SUB>0</SUB>; iii) transit times of fast CMEs are
  only slightly influenced by the solar-wind speed. The last item is
  especially important for space-weather forecasting, since it reduces
  the number of key parameters that determine the arrival time of fast
  CMEs, which tend to be more geo-effective than the slow ones. Finally,
  we compared the drag-based model results with the observational data
  for two CME samples, consisting of non-interacting and interacting
  CMEs (Manoharan et al. in J. Geophys. Res.109, 2004). The comparison
  reveals that the model results are in better agreement with the
  observations for non-interacting events than for the interacting
  events. It was also found that for slow CMEs (v<SUB>0</SUB>&lt;500
  km s<SUP>−1</SUP>), there is a deviation between the observations
  and the model if slow-wind speeds (≈ 300 - 400 km s<SUP>−1</SUP>)
  are taken for the model input. On the other hand, the model values and
  the observed data agree for both the slow and the fast CMEs if higher
  solar-wind speeds are assumed. It is also found that the quadratic
  form of the drag equation reproduces the observed transit times of
  fast CMEs better than the linear drag model.

---------------------------------------------------------
Title: Kinematics of Interacting ICMEs and Related Forbush Decrease:
    Case Study
Authors: Maričić, D.; Vršnak, B.; Dumbović, M.; Žic, T.; Roša,
   D.; Hržina, D.; Lulić, S.; Romštajn, I.; Bušić, I.; Salamon, K.;
   Temmer, M.; Rollett, T.; Veronig, A.; Bostanjyan, N.; Chilingarian,
   A.; Mailyan, B.; Arakelyan, K.; Hovhannisyan, A.; Mujić, N.
2014SoPh..289..351M    Altcode:
  We study heliospheric propagation and some space weather aspects of
  three Earth-directed interplanetary coronal mass ejections (ICMEs),
  successively launched from the active region AR 11158 in the period
  13 - 15 February 2011. From the analysis of the ICME kinematics,
  morphological evolution, and in situ observations, we infer that the
  three ICMEs interacted on their way to Earth, arriving together at 1
  AU as a single interplanetary disturbance. Detailed analysis of the
  in situ data reveals complex internal structure of the disturbance,
  where signatures of the three initially independent ICMEs could be
  recognized. The analysis also reveals compression and heating of the
  middle ICME, as well as ongoing magnetic reconnection between the
  leading and the middle ICME. We present evidence showing that the
  propagation of these two, initially slower ICMEs, was boosted by the
  fastest, third ICME. Finally, we employ the ground-based cosmic ray
  observations, to show that this complex disturbance produced a single
  cosmic ray event, i.e., a simple Forbush decrease (FD). The results
  presented provide a better understanding of the ICME interactions and
  reveal effects that should be taken into account in forecasting of
  the arrival of such compound structures.

---------------------------------------------------------
Title: Initiation of Coronal Mass Ejections by Sunspot Rotation
Authors: Valori, G.; Török, T.; Temmer, M.; Veronig, A. M.; van
   Driel-Gesztelyi, L.; Vršnak, B.
2014IAUS..300..201V    Altcode:
  We report observations of a filament eruption, two-ribbon flare, and
  coronal mass ejection (CME) that occurred in Active Region NOAA 10898
  on 6 July 2006. The filament was located South of a strong sunspot that
  dominated the region. In the evolution leading up to the eruption, and
  for some time after it, a counter-clockwise rotation of the sunspot of
  about 30 degrees was observed. We suggest that the rotation triggered
  the eruption by progressively expanding the magnetic field above the
  filament. To test this scenario, we study the effect of twisting
  the initially potential field overlying a pre-existing flux rope,
  using three-dimensional zero-β MHD simulations. We consider a magnetic
  configuration whose photospheric flux distribution and coronal structure
  is guided by the observations and a potential field extrapolation. We
  find that the twisting leads to the expansion of the overlying field. As
  a consequence of the progressively reduced magnetic tension, the flux
  rope quasi-statically adapts to the changed environmental field, rising
  slowly. Once the tension is sufficiently reduced, a distinct second
  phase of evolution occurs where the flux rope enters an unstable regime
  characterized by a strong acceleration. Our simulation thus suggests
  a new mechanism for the triggering of eruptions in the vicinity of
  rotating sunspots.

---------------------------------------------------------
Title: The Wave-Driver System of the Off-Disk Coronal Wave of 17
    January 2010
Authors: Temmer, M.; Vrsnak, B.; Veronig, A. M.
2013SoPh..287..441T    Altcode: 2012arXiv1207.2857T; 2012SoPh..tmp..194T
  We study the 17 January 2010 flare-CME-wave event by using
  STEREO/SECCHI-EUVI and -COR1 data. The observational study is combined
  with an analytic model that simulates the evolution of the coronal wave
  phenomenon associated with the event. From EUV observations, the wave
  signature appears to be dome shaped having a component propagating
  on the solar surface (\overline{v}≈280~km s^{-1}) as well as one
  off-disk (\overline{v}≈ 600~km s^{-1}) away from the Sun. The off-disk
  dome of the wave consists of two enhancements in intensity, which
  conjointly develop and can be followed up to white-light coronagraph
  images. Applying an analytic model, we derive that these intensity
  variations belong to a wave-driver system with a weakly shocked wave,
  initially driven by expanding loops, which are indicative of the early
  evolution phase of the accompanying CME. We obtain the shock standoff
  distance between wave and driver from observations as well as from
  model results. The shock standoff distance close to the Sun (&lt; 0.3
  R<SUB>⊙</SUB> above the solar surface) is found to rapidly increase
  with values of ≈ 0.03 - 0.09 R<SUB>⊙</SUB>, which gives evidence
  of an initial lateral (over)expansion of the CME. The kinematical
  evolution of the on-disk wave could be modeled using input parameters
  that require a more impulsive driver (duration t=90 s, acceleration
  a=1.7 km s<SUP>−2</SUP>) compared to the off-disk component (duration
  t=340 s, acceleration a=1.5 km s<SUP>−2</SUP>).

---------------------------------------------------------
Title: Comparison of geoeffectiveness of coronal mass ejections and
    corotating interaction regions
Authors: Verbanac, G.; Živković, S.; Vršnak, B.; Bandić, M.;
   Hojsak, T.
2013A&A...558A..85V    Altcode:
  Context. A detailed comparison of the geomagnetic responses to
  interplanetary coronal mass ejection (ICMEs) and corotating interaction
  regions (CIRs) during solar cycle 23 was performed using geomagnetic
  indices Dst, Ap, and AE. <BR /> Aims: We aim to find out if there
  are relative differences in the response of various magnetospheric
  current systems to the impact of ICMEs and CIRs. In addition, we are
  exploring the possibility of forecasting geomagnetic activity using the
  coronagraphic observations of the ICME take-off. <BR /> Methods: The
  peak values of the plasma characteristics of ICMEs and CIRs (velocity V,
  magnetic field B, and BV related to the electric field), and geomagnetic
  indices were investigated by applying the linear and power-law cross
  correlation analysis. The influence of the time-resolution on the
  results was performed for two time resolutions obtained by one-hour
  (three-hour for Ap) and six-hour data averaging. <BR /> Results:
  For ICMEs the power-law fits are found to be important only for the
  relationships between BV and geomagnetic indices. For Ap and Dst, there
  is no difference between the one-hour (three-hour for Ap) and six-hour
  option. For AE, the one-hour data distribution shows more clearly the
  non-linear dependence on BV. Our data set shows that below BV ~ 5 mV
  m<SUP>-1</SUP> ICMEs have practically no geomagnetic effect at low and
  mid latitudes, but at high latitudes at least some geomagnetic activity
  will be triggered. For all HSS/CIRs dependencies, a power law is found
  to better describe the data than the linear fit. The data distributions
  show that BV has to reach ~4 mV m<SUP>-1</SUP> in order to drive at
  least some geomagnetic activity at all latitudes. We observed that
  there are fast CMEs that have almost no geomagnetic effect at low and
  mid latitudes. On the other hand, at high latitudes, fast CMEs always
  trigger some geomagnetic activity. This might be have implications
  for space weather forecasting. <BR /> Conclusions: Magnetospheric
  response to both solar drivers (ICMEs and CIRs) is different at various
  latitudes, thus results in different development of various current
  systems within the Earth's magnetosphere and ionosphere. Furthermore,
  we show that ICMEs and CIRs cause different geomagnetic activity. In
  the case of ICMEs equatorial current system responses in a linear
  manner, while the response of the polar-current system is likely to
  be non-linear. For HSS/CIRs, apparently all current systems respond
  in a non-linear way, especially the polar current system.

---------------------------------------------------------
Title: Initiation of Coronal Mass Ejections by Sunspot Rotation
Authors: Török, T.; Temmer, M.; Valori, G.; Veronig, A. M.; van
   Driel-Gesztelyi, L.; Vršnak, B.
2013SoPh..286..453T    Altcode: 2014arXiv1401.2922T
  We study a filament eruption, two-ribbon flare, and coronal mass
  ejection (CME) that occurred in NOAA Active Region 10898 on 6 July
  2006. The filament was located South of a strong sunspot that dominated
  the region. In the evolution leading up to the eruption, and for some
  time after it, a counter-clockwise rotation of the sunspot of about
  30 degrees was observed. We suggest that the rotation triggered the
  eruption by progressively expanding the magnetic field above the
  filament. To test this scenario, we study the effect of twisting
  the initially potential field overlying a pre-existing flux-rope,
  using three-dimensional zero-β MHD simulations. We first consider
  a relatively simple and symmetric system, and then study a more
  complex and asymmetric magnetic configuration, whose photospheric-flux
  distribution and coronal structure are guided by the observations and a
  potential field extrapolation. In both cases, we find that the twisting
  leads to the expansion of the overlying field. As a consequence of the
  progressively reduced magnetic tension, the flux-rope quasi-statically
  adapts to the changed environmental field, rising slowly. Once the
  tension is sufficiently reduced, a distinct second phase of evolution
  occurs where the flux-rope enters an unstable regime characterised by
  a strong acceleration. Our simulations thus suggest a new mechanism
  for the triggering of eruptions in the vicinity of rotating sunspots.

---------------------------------------------------------
Title: Formation of Coronal Shock Waves
Authors: Lulić, S.; Vršnak, B.; Žic, T.; Kienreich, I. W.; Muhr,
   N.; Temmer, M.; Veronig, A. M.
2013SoPh..286..509L    Altcode: 2013arXiv1303.2786L
  Magnetosonic wave formation driven by an expanding cylindrical
  piston is numerically simulated to obtain better physical insight
  into the initiation and evolution of large-scale coronal waves caused
  by coronal eruptions. Several very basic initial configurations are
  employed to analyze intrinsic characteristics of MHD wave formation
  that do not depend on specific properties of the environment. It turns
  out that these simple initial configurations result in piston/wave
  morphologies and kinematics that reproduce common characteristics of
  coronal waves. In the initial stage, the wave and the expanding source
  region cannot be clearly resolved; i.e. a certain time is needed before
  the wave detaches from the piston. Thereafter, it continues to travel
  as what is called a "simple wave." During the acceleration stage of the
  source region inflation, the wave is driven by the piston expansion, so
  its amplitude and phase-speed increase, whereas the wavefront profile
  steepens. At a given point, a discontinuity forms in the wavefront
  profile; i.e. the leading edge of the wave becomes shocked. The
  time/distance required for the shock formation is shorter for a more
  impulsive source-region expansion. After the piston stops, the wave
  amplitude and phase speed start to decrease. During the expansion,
  most of the source region becomes strongly rarefied, which reproduces
  the coronal dimming left behind the eruption. However, the density
  increases at the source-region boundary, and stays enhanced even after
  the expansion stops, which might explain stationary brightenings
  that are sometimes observed at the edges of the erupted coronal
  structure. Also, in the rear of the wave a weak density depletion
  develops, trailing the wave, which is sometimes observed as weak
  transient coronal dimming. Finally, we find a well-defined relationship
  between the impulsiveness of the source-region expansion and the wave
  amplitude and phase speed. The results for the cylindrical piston are
  also compared with the outcome for a planar wave that is formed by a
  one-dimensional piston, to find out how different geometries affect
  the evolution of the wave.

---------------------------------------------------------
Title: Solar TErrestrial Relations Observatory-A (STEREO-A) and
    PRoject for On-Board Autonomy 2 (PROBA2) Quadrature Observations of
    Reflections of Three EUV Waves from a Coronal Hole
Authors: Kienreich, I. W.; Muhr, N.; Veronig, A. M.; Berghmans, D.;
   De Groof, A.; Temmer, M.; Vršnak, B.; Seaton, D. B.
2013SoPh..286..201K    Altcode: 2012SoPh..tmp..138K
  We investigate the interaction of three consecutive large-scale coronal
  waves with a polar coronal hole, simultaneously observed on-disk by the
  Solar TErrestrial Relations Observatory (STEREO)-A spacecraft and on
  the limb by the PRoject for On-Board Autonomy 2 (PROBA2) spacecraft on
  27 January 2011. All three extreme ultraviolet (EUV) waves originate
  from the same active region, NOAA 11149, positioned at N30E15 in the
  STEREO-A field of view and on the limb in PROBA2. For the three primary
  EUV waves, we derive starting velocities in the range of ≈ 310 km
  s<SUP>−1</SUP> for the weakest up to ≈ 500 km s<SUP>−1</SUP>
  for the strongest event. Each large-scale wave is reflected at the
  border of the extended coronal hole at the southern polar region. The
  average velocities of the reflected waves are found to be smaller than
  the mean velocities of their associated direct waves. However, the
  kinematical study also reveals that in each case the ending velocity
  of the primary wave matches the initial velocity of the reflected
  wave. In all three events, the primary and reflected waves obey the
  Huygens-Fresnel principle, as the incident angle with ≈ 10° to
  the normal is of the same magnitude as the angle of reflection. The
  correlation between the speed and the strength of the primary EUV waves,
  the homologous appearance of both the primary and the reflected waves,
  and in particular the EUV wave reflections themselves suggest that the
  observed EUV transients are indeed nonlinear large-amplitude MHD waves.

---------------------------------------------------------
Title: Propagation of Interplanetary Coronal Mass Ejections: The
    Drag-Based Model
Authors: Vršnak, B.; Žic, T.; Vrbanec, D.; Temmer, M.; Rollett, T.;
   Möstl, C.; Veronig, A.; Čalogović, J.; Dumbović, M.; Lulić, S.;
   Moon, Y. -J.; Shanmugaraju, A.
2013SoPh..285..295V    Altcode: 2012SoPh..tmp..124V
  We present the "Drag-Based Model" (DBM) of heliospheric propagation
  of interplanetary coronal mass ejections (ICMEs). The DBM is based on
  the hypothesis that the driving Lorentz force, which launches a CME,
  ceases in the upper corona and that beyond a certain distance the
  dynamics becomes governed solely by the interaction of the ICME and
  the ambient solar wind. In particular, we consider the option where
  the drag acceleration has a quadratic dependence on the ICME relative
  speed, which is expected in a collisionless environment, where the
  drag is caused primarily by emission of magnetohydrodynamic (MHD)
  waves. In this paper we present the simplest version of DBM, where
  the equation of motion can be solved analytically, providing explicit
  solutions for the Sun-Earth ICME transit time and impact speed. This
  offers easy handling and straightforward application to real-time
  space-weather forecasting. Beside presenting the model itself, we
  perform an analysis of DBM performances, applying a statistical and
  case-study approach, which provides insight into the advantages and
  drawbacks of DBM. Finally, we present a public, DBM-based, online
  forecast tool.

---------------------------------------------------------
Title: Evolution of CMEs in the inner heliosphere - observations
    versus models
Authors: Temmer, Manuela; Vrsnak, Bojan; Möstl, Christian; Veronig,
   Astrid; Rollett, Tanja; Bein, Bianca
2013EGUGA..15.1328T    Altcode:
  With the SECCHI instrument suite aboard STEREO, coronal mass ejections
  (CMEs) can be observed from multiple vantage points during their entire
  propagation all the way from the Sun to 1 AU. The propagation behavior
  of CMEs in the interplanetary space is mainly influenced by the ambient
  solar wind flow. CMEs that are faster than the ambient solar wind get
  decelerated, whereas slower ones are accelerated until the CME speed
  is finally adjusted to the solar wind speed. On a statistical basis,
  empirical models taking into account the drag force acting on CMEs,
  are able to describe the observed kinematical behaviors. For several
  well observed events, we will present a comparative study showing
  the kinematical evolution of CMEs derived from remote sensing and
  in situ data, as well as from empirical models using 2D and 3D input
  parameters. From this we aim to obtain the distance regime at which
  the solar wind drag force is dominating the CME propagation.

---------------------------------------------------------
Title: Radial evolution of magnetic cloud properties
Authors: Rollett, Tanja; Veronig, Astrid M.; Leitner, Martin; Vrsnak,
   Bojan; Möstl, Christian; Farrugia, Charles J.; Temmer, Manuela
2013EGUGA..15.2710R    Altcode:
  Magnetic clouds (MCs) are characterized as intervals of enhanced,
  smoothly rotating interplanetary magnetic field, low plasma beta and
  temperature in spacecraft in situ data and can be part of ICMEs. In
  this study we analyze the radial evolution of MCs using a sample of
  events detected by radial aligned spacecrafts at different heliocentric
  distances. The data-sets are fitted with a force-free, constant-alpha
  flux rope model. Using the outcome of this fitting model we calculate
  the estimated cross section diameter (assuming a cylindrical flux tube),
  the poloidal and the axial magnetic field, the current, the magnetic
  flux and the inductance. All these parameter are further studied as a
  function of heliocentric distance. Strong variations of the current or
  the magnetic flux could be a hint for magnetic reconnection between
  the MC and the solar wind. This work has received funding from the
  European Commission FP7 Project COMESEP (263252).

---------------------------------------------------------
Title: The chaotic solar cycle. II. Analysis of cosmogenic
    <SUP>10</SUP>Be data
Authors: Hanslmeier, A.; Brajša, R.; Čalogović, J.; Vršnak,
   B.; Ruždjak, D.; Steinhilber, F.; MacLeod, C. L.; Ivezić, Ž.;
   Skokić, I.
2013A&A...550A...6H    Altcode: 2014arXiv1402.2776H
  Context. The variations of solar activity over long time intervals using
  a solar activity reconstruction based on the cosmogenic radionuclide
  <SUP>10</SUP>Be measured in polar ice cores are studied. <BR /> Aims:
  The periodicity of the solar activity cycle is studied. The solar
  activity cycle is governed by a complex dynamo mechanism. Methods
  of nonlinear dynamics enable us to learn more about the regular
  and chaotic behavior of solar activity. In this work we compare
  our earlier findings based on <SUP>14</SUP>C data with the results
  obtained using <SUP>10</SUP>Be data. <BR /> Methods: By applying
  methods of nonlinear dynamics, the solar activity cycle is studied
  using solar activity proxies that have been reaching into the past
  for over 9300 years. The complexity of the system is expressed by
  several parameters of nonlinear dynamics, such as embedding dimension
  or false nearest neighbors, and the method of delay coordinates is
  applied to the time series. We also fit a damped random walk model,
  which accurately describes the variability of quasars, to the solar
  <SUP>10</SUP>Be data and investigate the corresponding power spectral
  distribution. The periods in the data series were searched by the
  Fourier and wavelet analyses. <BR /> Results: The solar activity on the
  long-term scale is found to be on the edge of chaotic behavior. This
  can explain the observed intermittent period of longer lasting solar
  activity minima. Filtering the data by eliminating variations below
  a certain period (the periods of 380 yr and 57 yr were used) yields a
  far more regular behavior of solar activity. A comparison between the
  results for the <SUP>10</SUP>Be data with the <SUP>14</SUP>C data shows
  many similarities. Both cosmogenic isotopes are strongly correlated
  mutually and with solar activity. Finally, we find that a series of
  damped random walk models provides a good fit to the <SUP>10</SUP>Be
  data with a fixed characteristic time scale of 1000 years, which is
  roughly consistent with the quasi-periods found by the Fourier and
  wavelet analyses. <BR /> Conclusions: The time series of solar activity
  proxies used here clearly shows that solar activity behaves differently
  from random data. The unfiltered data exhibit a complex dynamics that
  becomes more regular when filtering the data. The results indicate
  that solar activity proxies are also influenced by other than solar
  variations and reflect solar activity only on longer time scales.

---------------------------------------------------------
Title: The Successive CME on 13th; 14th and 15th February 2011 and
    Forbush decrease on 18 February 2011
Authors: Maričić, D.; Bostasyan, N.; Dumbović, M.; Chilingarian,
   A.; Mailyan, B.; Rostomyan, H.; Arakelyan, K.; Vršnak, B.; Roša,
   D.; Hržina, D.; Romštajn, I.; Veronig, A.
2013JPhCS.409a2158M    Altcode:
  Aims. We analyze the kinematics of three interplanetary coronal mass
  ejections (ICMEs) that occurred on 13th, 14th and 15th February
  2011 in the active region AR 11155 and have shown that they
  appeared at the Earth orbit on February, 18th and caused Forbush
  decrease (FD). Methods. The solar coordinates of flares are (S19W03),
  (S20W14) and (S21W18). The kinematic curves were obtained using STEREO
  (A&amp;B) data. Additionally, we explore the possibility of the CME-CME
  interaction for these three events. We compare obtained estimates of
  ICME arrival with the in-situ measurements from WIND satellite at
  L1 point and with ground-based cosmic ray data obtained from SEVAN
  network. Results. The acceleration of each CME is highly correlated
  with the associated SXR flares energy release. CMEs that erupted at 13
  and 14 Feb 2011 are not associated with prominence eruption; maximum
  velocity was v<SUB>max</SUB>550 ± 50 km/s and v<SUB>max</SUB>400
  ± 50 km/s, respectively. However, 15 Feb 2011 CME is connected with
  much more violent eruption associated with a prominence, with maximum
  velocity of v<SUB>max</SUB> 1400 ± 50 km/s. The last overtakes 13th
  and 14th Feb CMEs at distances of 32 and 160 Rsolar, respectively.

---------------------------------------------------------
Title: Solar eruptive filament studies at USO for the COMESEP project
Authors: Srivastava, N.; Crosby, N.; Veronig, A.; Robrrecht, E.;
   Vršnak, B.; Vennerstrom, S.; Malandraki, O.; Dalla, S.; Rodriguez,
   L.; Hesse, M.; Odstrcil, D.
2013ASInC..10...67S    Altcode:
  The Coronal Mass Ejections and Solar Energetic Particles (COMESEP)
  project is developing tools for forecasting geomagnetic storms and solar
  energetic particle (SEP) radiation storms. By analysis of historical
  solar and interplanetary data, complemented with the extensive data
  coverage of solar cycle 23, the key ingredients that lead to geomagnetic
  storms, SEP events and the factors that are responsible for false
  alarms are being identified. Based on the insights gained, and making
  use of algorithms for the automated detection of CMEs, forecasting
  tools for geomagnetic and SEP radiation storms will be developed and
  optimised. Validation and implementation of the developed tools into
  an operational Space Weather Alert system will be performed. COMESEP
  is a unique cross collaboration effort and bridges the gap between the
  SEP, CME and terrestrial effects scientific communities. The role of
  the Udaipur Solar Observatory (USO) in addressing some of the goals
  of this project are highlighted in this paper. In particular, USO is
  engaged in studying the CMEs associated with eruptive filaments. We
  describe the studies undertaken to understand space weather effects
  related to these CMEs.

---------------------------------------------------------
Title: Relation Between Coronal Hole Areas on the Sun and the Solar
    Wind Parameters at 1 AU
Authors: Rotter, T.; Veronig, A. M.; Temmer, M.; Vršnak, B.
2012SoPh..281..793R    Altcode: 2012SoPh..tmp..202R
  We analyze the relationship between the coronal hole (CH)
  characteristics on the Sun (area, position, and intensity levels)
  and the corresponding solar wind parameters (solar wind speed v,
  proton temperature T, proton density n, and magnetic field strength B)
  measured in situ at 1 AU with a 6-h time resolution. We developed a
  histogram-based intensity thresholding method to obtain fractional CH
  areas from SOHO/EIT 195 Å images. The algorithm was applied to 6-h
  cadence EIT 195 Å images for the year 2005, which were characterized
  by a low solar activity. In calculating well-defined peaks of the solar
  wind parameters corresponding to the peaks in CH area, we found that the
  solar wind speed v shows a high correlation with correlation coefficient
  cc=0.78, medium correlation for T and B with cc=0.41 and cc=0.41. No
  significant correlation was found with the proton density n. Applying
  an intensity-weighted CH area did not improve the relations, since
  the size and the mean intensity of the CH areas are not independent
  parameters but strongly correlated (cc=− 0.72). Comparison of the
  fractional CH areas derived from GOES/SXI and SOHO/EIT and the related
  solar wind predictions shows no systematic differences (cc=0.79).

---------------------------------------------------------
Title: Coronal Mass Ejection of 26 February 2000: Complete analysis
    of the three-part CME structure
Authors: Maričić, D.; Vršnak, B.; Roša, D.; Hržina, D.
2012SunGe...7...85M    Altcode:
  We analyze the kinematics and morphology of the limb coronal mass
  ejection (CME) of 26 February 2000, utilizing observations from Mauna
  Loa Solar Observatory (MLSO), the Solar and Heliospheric Observatory
  (SOHO) and the Geostationary Operational Environmental Satellite
  (GOES). Also, we analyze the relation between dynamics of the CME and
  the energy release in the associated flare. <P />An intricate structure
  (prominence, prominence-like absorbing feature, cavity and bright
  overlying arcade) is clearly recognizable in the low corona during
  the pre-eruption phase of slow rise. This provided measurements of
  kinematics of verious features from the very beginning of the eruption
  up to the post-acceleration phase which was followed up to 32 solar
  radii. Such events are observed only occasionaly, and are of great
  importance for the comprehension of the nature of forces driving
  CMEs. The acceleration maximum was attained at the radial distance
  of 2.4 solar radii from the solar center and ceased beyond 12 solar
  radii. The time profiles of the acceleration of various features
  of CME are showing "self-similar" expansion and implying a common
  driver. The acceleration phase was synchronized to a certain degree with
  the impulsive phase of the associated two-ribbon flare. Observations
  provide clear evidence that CME eruption caused a global restructuring
  of the magnetic field in the outer and inner corona. Furthermore,
  kinematics and morphological properties of this CME show possibility
  that in some events the prominence can evolve into a structure which
  looks like three-part structure CME, i.e. where the frontal rim is
  just a part of helically twisted prominence.

---------------------------------------------------------
Title: Impulsive Acceleration of Coronal Mass Ejections. II. Relation
    to Soft X-Ray Flares and Filament Eruptions
Authors: Bein, B. M.; Berkebile-Stoiser, S.; Veronig, A. M.; Temmer,
   M.; Vršnak, B.
2012ApJ...755...44B    Altcode: 2012arXiv1206.2144B
  Using high time cadence images from the STEREO EUVI, COR1, and COR2
  instruments, we derived detailed kinematics of the main acceleration
  stage for a sample of 95 coronal mass ejections (CMEs) in comparison
  with associated flares and filament eruptions. We found that CMEs
  associated with flares reveal on average significantly higher peak
  accelerations and lower acceleration phase durations, initiation
  heights, and heights, at which they reach their peak velocities and peak
  accelerations. This means that CMEs that are associated with flares are
  characterized by higher and more impulsive accelerations and originate
  from lower in the corona where the magnetic field is stronger. For CMEs
  that are associated with filament eruptions we found only for the CME
  peak acceleration significantly lower values than for events that were
  not associated with filament eruptions. The flare rise time was found
  to be positively correlated with the CME acceleration duration and
  negatively correlated with the CME peak acceleration. For the majority
  of the events the CME acceleration starts before the flare onset (for
  75% of the events) and the CME acceleration ends after the soft X-ray
  (SXR) peak time (for 77% of the events). In ~60% of the events, the
  time difference between the peak time of the flare SXR flux derivative
  and the peak time of the CME acceleration is smaller than ±5 minutes,
  which hints at a feedback relationship between the CME acceleration and
  the energy release in the associated flare due to magnetic reconnection.

---------------------------------------------------------
Title: Forecasting Geomagnetic Storms and Solar Energetic Particle
Events: the COMESEP Project
Authors: Crosby, N.; Veronig, A.; Robbrecht, E.; Vrsnak, B.;
   Vennerstrøm, S.; Malandraki, O.; Dalla, S.; Srivastava, N.; Hesse,
   M.; Odstrcil, D.
2012EGUGA..1412544C    Altcode:
  COMESEP (COronal Mass Ejections and Solar Energetic Particles),
  funded by the European Union Framework 7 programme, is a three-year
  collaborative project that has been running for one year. Tools for
  forecasting geomagnetic storms and solar energetic particle (SEP)
  radiation storms are being developed under the project. By analysis
  of historical data, complemented by the extensive data coverage of
  solar cycle 23, the key ingredients that lead to magnetic storms and
  SEP events and the factors that are responsible for false alarms are
  being identified. To enhance our understanding of the 3D kinematics
  and interplanetary propagation of coronal mass ejections (CMEs), the
  structure, propagation and evolution of CMEs are being investigated. In
  parallel, the sources and propagation of SEPs are being examined and
  modeled. Based on the insights gained, and making use of algorithms for
  the automated detection of CMEs, forecasting tools for geomagnetic and
  SEP radiation storms are being developed and optimised. Validation and
  implementation of the produced tools into an operational Space Weather
  Alert system will be performed. Geomagnetic and SEP radiation storm
  alerts will be based on the COMESEP definition of risk. COMESEP is a
  unique cross-collaboration effort and bridges the gap between the SEP
  and CME scientific communities. For more information about the project,
  see the COMESEP website http://www.comesep.eu/ . This work has received
  funding from the European Commission FP7 Project COMESEP (263252).

---------------------------------------------------------
Title: STEREO-A and PROBA2 Quadrature Observations of Reflections
    of three EUV Waves from a Coronal Hole
Authors: Kienreich, Ines Waltraud; Muhr, Nicole; Veronig, Astrid;
   Berghmans, David; de Groof, Anik; Temmer, Manuela; Vršnak, Bojan;
   Seaton, Dan
2012arXiv1204.6472K    Altcode: 2012arXiv1204.6472W
  We investigate the interaction of three consecutive large-scale coronal
  waves with a polar coronal hole, simultaneously observed on-disk by the
  Solar TErrestrial Relations Observatory (STEREO)-A spacecraft and on
  the limb by the PRoject for On-Board Autonomy 2 (PROBA2) spacecraft on
  January 27, 2011. All three extreme-ultraviolet(EUV) waves originate
  from the same active region NOAA 11149 positioned at N30E15 in the
  STEREO-A field-of-view and on the limb in PROBA2. We derive for the
  three primary EUV waves start velocities in the range of ~310 km/s for
  the weakest up to ~500 km/s for the strongest event. Each large-scale
  wave is reflected at the border of the extended coronal hole at the
  southern polar region. The average velocities of the reflected waves
  are found to be smaller than the mean velocities of their associated
  direct waves. However, the kinematical study also reveals that in each
  case the end velocity of the primary wave matches the initial velocity
  of the reflected wave. In all three events the primary and reflected
  waves obey the Huygens-Fresnel principle, as the incident angle with
  ~10° to the normal is of the same size as the angle of reflection. The
  correlation between the speed and the strength of the primary EUV waves,
  the homologous appearance of both the primary and the reflected waves,
  and in particular the EUV wave reflections themselves implicate that the
  observed EUV transients are indeed nonlinear large-amplitude MHD waves.

---------------------------------------------------------
Title: Commission 10: Solar Activity
Authors: van Driel-Gesztelyi, Lidia; Schrijver, Carolus J.; Klimchuk,
   James A.; Charbonneau, Paul; Fletcher, Lyndsay; Hasan, S. Sirajul;
   Hudson, Hugh S.; Kusano, Kanya; Mandrini, Cristina H.; Peter, Hardi;
   Vršnak, Bojan; Yan, Yihua
2012IAUTA..28...69V    Altcode:
  Commission 10 of the International Astronomical Union has more than
  650 members who study a wide range of activity phenomena produced by
  our nearest star, the Sun. Solar activity is intrinsically related
  to solar magnetic fields and encompasses events from the smallest
  energy releases (nano- or even picoflares) to the largest eruptions
  in the Solar System, coronal mass ejections (CMEs), which propagate
  into the Heliosphere reaching the Earth and beyond. Solar activity is
  manifested in the appearance of sunspot groups or active regions, which
  are the principal sources of activity phenomena from the emergence of
  their magnetic flux through their dispersion and decay. The period
  2008-2009 saw an unanticipated extended solar cycle minimum and
  unprecedentedly weak polar-cap and heliospheric field. Associated with
  that was the 2009 historical maximum in galactic cosmic rays flux since
  measurements begun in the middle of the 20th Century. Since then Cycle
  24 has re-started solar activity producing some spectacular eruptions
  observed with a fleet of spacecraft and ground-based facilities. In
  the last triennium major advances in our knowledge and understanding
  of solar activity were due to continuing success of space missions as
  SOHO, Hinode, RHESSI and the twin STEREO spacecraft, further enriched
  by the breathtaking images of the solar atmosphere produced by the
  Solar Dynamic Observatory (SDO) launched on 11 February 2010 in the
  framework of NASA's Living with a Star program. In August 2012, at the
  time of the IAU General Assembly in Beijing when the mandate of this
  Commission ends, we will be in the unique position to have for the
  first time a full 3-D view of the Sun and solar activity phenomena
  provided by the twin STEREO missions about 120 degrees behind and
  ahead of Earth and other spacecraft around the Earth and ground-based
  observatories. These new observational insights are continuously
  posing new questions, inspiring and advancing theoretical analysis
  and modelling, improving our understanding of the physics underlying
  magnetic activity phenomena. Commission 10 reports on a vigorously
  evolving field of research produced by a large community. The number
  of refereed publications containing `Sun', `heliosphere', or a synonym
  in their abstracts continued the steady growth seen over the preceding
  decades, reaching about 2000 in the years 2008-2010, with a total of
  close to 4000 unique authors. This report, however, has its limitations
  and it is inherently incomplete, as it was prepared jointly by the
  members of the Organising Committee of Commission 10 (see the names
  of the primary contributors to the sections indicated in parentheses)
  reflecting their fields of expertise and interest. Nevertheless, we
  believe that it is a representative sample of significant new results
  obtained during the last triennium in the field of solar activity.

---------------------------------------------------------
Title: CME-CME interaction during the 2010 August 1 events
Authors: Temmer, M.; Vrsnak, B.; Rollett, T.; Bein, B.; deKoning,
   C. A.; Liu, Y.; Bosman, E.; Davies, J. A.; Möstl, C.; Zic, T.;
   Veronig, A. M.; Bothmer, V.; Harrison, R.; Nitta, N.; Bisi, M.; Flor,
   O.; Eastwood, J.; Odstrcil, D.; Forsyth, R.
2012EGUGA..14.1677T    Altcode:
  We study a CME-CME interaction that occurred during the 2010 August 1
  events using STEREO/SECCHI data (COR and HI). The CMEs were Earth
  directed where clear signatures of magnetic flux ropes could be
  measured from in situ Wind data. To give evidence of the actual
  interaction we derive the direction of motion for both CMEs applying
  several independent methods. From this we obtain that both CMEs head
  into similar directions enabling us to actually observe the merging
  in the HI1 field-of-view (and rule out the possibility that this is
  just a line of sight effect). The full de-projected kinematics of the
  faster CME from Sun to Earth is derived when combining data points from
  remote observations with in situ parameters of the ICME measured at
  1 AU. We study the evolution of the kinematical profile of the faster
  CME by applying a drag based model.

---------------------------------------------------------
Title: Characteristics of Kinematics of a Coronal Mass Ejection
    during the 2010 August 1 CME-CME Interaction Event
Authors: Temmer, Manuela; Vršnak, Bojan; Rollett, Tanja; Bein, Bianca;
   de Koning, Curt A.; Liu, Ying; Bosman, Eckhard; Davies, Jackie A.;
   Möstl, Christian; Žic, Tomislav; Veronig, Astrid M.; Bothmer, Volker;
   Harrison, Richard; Nitta, Nariaki; Bisi, Mario; Flor, Olga; Eastwood,
   Jonathan; Odstrcil, Dusan; Forsyth, Robert
2012ApJ...749...57T    Altcode: 2012arXiv1202.0629T
  We study the interaction of two successive coronal mass ejections (CMEs)
  during the 2010 August 1 events using STEREO/SECCHI COR and heliospheric
  imager (HI) data. We obtain the direction of motion for both CMEs by
  applying several independent reconstruction methods and find that the
  CMEs head in similar directions. This provides evidence that a full
  interaction takes place between the two CMEs that can be observed in the
  HI1 field of view. The full de-projected kinematics of the faster CME
  from Sun to Earth is derived by combining remote observations with in
  situ measurements of the CME at 1 AU. The speed profile of the faster
  CME (CME2; ~1200 km s<SUP>-1</SUP>) shows a strong deceleration over
  the distance range at which it reaches the slower, preceding CME (CME1;
  ~700 km s<SUP>-1</SUP>). By applying a drag-based model we are able
  to reproduce the kinematical profile of CME2, suggesting that CME1
  represents a magnetohydrodynamic obstacle for CME2 and that, after
  the interaction, the merged entity propagates as a single structure
  in an ambient flow of speed and density typical for quiet solar wind
  conditions. Observational facts show that magnetic forces may contribute
  to the enhanced deceleration of CME2. We speculate that the increase
  in magnetic tension and pressure, when CME2 bends and compresses the
  magnetic field lines of CME1, increases the efficiency of drag.

---------------------------------------------------------
Title: Flare-generated Type II Burst without Associated Coronal
    Mass Ejection
Authors: Magdalenić, J.; Marqué, C.; Zhukov, A. N.; Vršnak, B.;
   Veronig, A.
2012ApJ...746..152M    Altcode:
  We present a study of the solar coronal shock wave on 2005 November
  14 associated with the GOES M3.9 flare that occurred close to the
  east limb (S06° E60°). The shock signature, a type II radio burst,
  had an unusually high starting frequency of about 800 MHz, indicating
  that the shock was formed at a rather low height. The position of the
  radio source, the direction of the shock wave propagation, and the
  coronal electron density were estimated using Nançay Radioheliograph
  observations and the dynamic spectrum of the Green Bank Solar Radio
  Burst Spectrometer. The soft X-ray, Hα, and Reuven Ramaty High Energy
  Solar Spectroscopic Imager observations show that the flare was compact,
  very impulsive, and of a rather high density and temperature, indicating
  a strong and impulsive increase of pressure in a small flare loop. The
  close association of the shock wave initiation with the impulsive
  energy release suggests that the impulsive increase of the pressure
  in the flare was the source of the shock wave. This is supported by
  the fact that, contrary to the majority of events studied previously,
  no coronal mass ejection was detected in association with the shock
  wave, although the corresponding flare occurred close to the limb.

---------------------------------------------------------
Title: Cosmic ray modulation by different types of solar wind
    disturbances
Authors: Dumbović, M.; Vršnak, B.; Čalogović, J.; Župan, R.
2012A&A...538A..28D    Altcode:
  Context. Solar wind disturbances such as interplanetary coronal
  mass ejections (ICMEs) and corotating interaction regions (CIRs)
  cause short-term cosmic ray depressions, generally denoted as Forbush
  decreases. <BR /> Aims: We conduct a systematic statistical study of
  various aspects of Forbush decreases. The analysis provides empirical
  background for physical interpretations of short-term cosmic ray
  modulations. <BR /> Methods: Firstly, we analyzed the effects of
  different types of solar wind disturbances, and secondly, we focused
  on the phenomenon of over-recovery (the return of the cosmic ray
  count to a value higher than the pre-decrease level). The analysis
  is based on ground-based neutron monitor data and the solar wind
  data recorded by the Advanced Composition Explorer. The correlations
  between various cosmic ray depressions and solar wind parameters as
  well as their statistical significance are analyzed in detail. In
  addition, we performed a normalized superposed epoch analysis for
  depressions and magnetic field enhancements. <BR /> Results: The
  analysis revealed differences in the relationship between different
  solar wind disturbances and cosmic ray depression parameters. The
  amplitude of the depression for ICMEs was found to correlate well
  with the amplitudes of magnetic field strength and fluctuations,
  whereas for CIRs we found only the correlation between the amplitude
  of the depression and the solar wind disturbance dimension proxy
  vt<SUB>B</SUB>. Similar behavior was found for shock and no-shock
  events, respectively. The CIR/ICME composites show a specific
  behavior that is a mixture of both ICMEs and CIRs. For all analyzed
  categories we found that the duration of the depression correlates
  with the duration of the solar wind disturbance. The analysis of the
  over-recovery showed that there is no straightforward relationship to
  either "branching-effect" or geomagnetic effects, therefore we propose
  a scenario where the "branching-effect" is caused by several factors
  and is only indirectly related to the over-recovery.

---------------------------------------------------------
Title: Solar influences on the short-term cosmic ray modulation
Authors: Dumbović, M.; Vršnak, B.; Čalogović, J.
2012CEAB...36...65D    Altcode:
  This study aims to provide a quantitative basis for physical
  interpretations of Forbush decreases (FDs) caused by disturbances in the
  interplanetary magnetic field. A superposed epoch analysis is applied
  to the magnetic field strength and fluctuations data obtained from the
  Advanced Composition Explorer, and to the cosmic ray data obtained
  from ground level neutron monitors. We found that the morphology,
  as well as the amplitude and duration of FDs, are dependent on the
  type of the disturbance that caused the FD.

---------------------------------------------------------
Title: Characteristics of DH type II bursts, CMEs and flares with
    respect to the acceleration of CMEs
Authors: Prakash, O.; Umapathy, S.; Shanmugaraju, A.; Pappa Kalaivani,
   P.; Vršnak, Bojan
2012Ap&SS.337...47P    Altcode: 2011Ap&SS.tmp..608P
  A detailed investigation on DH-type-II radio bursts recorded in
  Deca-Hectometer (hereinafter DH-type-II) wavelength range and their
  associated CMEs observed during the year 1997-2008 is presented. The
  sample of 212 DH-type-II associated with CMEs are classified into three
  populations: (i) Group I (43 events): DH-type-II associated CMEs are
  accelerating in the LASCO field view ( a&gt;15 m s<SUP>-2</SUP>);
  (ii) Group II (99 events): approximately constant velocity CMEs
  (-15&lt; a&lt;15 m s<SUP>-2</SUP>) and (iii) Group III (70 events):
  represents decelerating CMEs ( a&lt;-15 m s<SUP>-2</SUP>). Our study
  consists of three steps: (i) statistical properties of DH-type-II
  bursts of Group I, II and III events; (ii) analysis of time lags
  between onsets of flares and CMEs associated with DH-type-II bursts
  and (iii) statistical properties of flares and CMEs of Group I, II
  and III events. We found statistically significant differences between
  the properties of DH-type-II bursts of Group I, II and III events. The
  significance ( P <SUB> a </SUB>) is found using the one-way ANOVA-test
  to examine the differences between means of groups. For example, there
  is significant difference in the duration ( P <SUB> a </SUB>=5%),
  ending frequency ( P <SUB> a </SUB>=4%) and bandwidth ( P <SUB> a
  </SUB>=4%). The accelerating and decelerating CMEs have more kinetic
  energy than the constant speed CMEs. There is a significant difference
  between the nose height of CMEs at the end time of DH-type-IIs ( P <SUB>
  a </SUB>≪1%). From the time delay analysis, we found: (i) there is
  no significant difference in the delay (flare start—DH-type-II start
  and flare peak—DH-type-II start); (ii) small differences in the time
  delay between the CME onset and DH-type-II start, delay between the
  flare start and CME onset times. However, there are high significant
  differences in: flare duration ( P <SUB> a </SUB>=1%), flare rise time
  ( P <SUB> a </SUB>=0.5%), flare decay time ( P <SUB> a </SUB>=5%) and
  CMEs speed ( P <SUB> a </SUB>≪1%) of Group I, II and III events. The
  general LASCO CMEs have lower width and speeds when compared to the DH
  CMEs. It seems there is a strong relation between the kinetic energy
  of CMEs and DH-type-II properties.

---------------------------------------------------------
Title: Solar Hα and white light telescope at Hvar Observatory
Authors: Čalogović, J.; Dumbović, M.; Novak, N.; Vršnak, B.;
   Brajša, R.; Pötzi, W.; Hirtenfellner-Polanec, W.; Veronig, A.;
   Hanslmeier$, A.; Klvaňa, M.; Ambrož, P.
2012CEAB...36...83C    Altcode:
  Recently, the double solar telescope at Hvar Observatory was equipped
  with the fourth generation of acquisition hardware and software. It
  provides a valuable instrument to study rapid changes of chromospheric
  and photospheric features in great detail. The telescope consists of
  two Carl Zeiss refractors (photosphere d=217mm, chromosphere d=130mm)
  mounted as one unit on a German parallax mounting. Using a field
  of view of about 7 and 11 arcmin, it aims to produce high-resolution
  high-cadence imaging of active regions on the Sun. New Pulnix TM-4200GE
  12-bit CCD cameras allow to obtain time series with a cadence up to
  30 images per minute.

---------------------------------------------------------
Title: Plasma Diagnostics of an EIT Wave Observed by Hinode/EIS
    and SDO/AIA
Authors: Veronig, A. M.; Gömöry, P.; Kienreich, I. W.; Muhr, N.;
   Vršnak, B.; Temmer, M.; Warren, H. P.
2011ApJ...743L..10V    Altcode: 2011arXiv1111.3505V
  We present plasma diagnostics of an Extreme-Ultraviolet
  Imaging Telescope (EIT) wave observed with high cadence in
  Hinode/Extreme-Ultraviolet Imaging Spectrometer (EIS) sit-and-stare
  spectroscopy and Solar Dynamics Observatory/Atmospheric Imaging
  Assembly imagery obtained during the HOP-180 observing campaign on 2011
  February 16. At the propagating EIT wave front, we observe downward
  plasma flows in the EIS Fe XII, Fe XIII, and Fe XVI spectral lines
  (log T ≈ 6.1-6.4) with line-of-sight (LOS) velocities up to 20
  km s<SUP>-1</SUP>. These redshifts are followed by blueshifts with
  upward velocities up to -5 km s<SUP>-1</SUP> indicating relaxation
  of the plasma behind the wave front. During the wave evolution, the
  downward velocity pulse steepens from a few km s<SUP>-1</SUP> up to 20
  km s<SUP>-1</SUP> and subsequently decays, correlated with the relative
  changes of the line intensities. The expected increase of the plasma
  densities at the EIT wave front estimated from the observed intensity
  increase lies within the noise level of our density diagnostics from
  EIS Fe XIII 202/203 Å line ratios. No significant LOS plasma motions
  are observed in the He II line, suggesting that the wave pulse was not
  strong enough to perturb the underlying chromosphere. This is consistent
  with the finding that no Hα Moreton wave was associated with the
  event. The EIT wave propagating along the EIS slit reveals a strong
  deceleration of a ≈ -540 m s<SUP>-2</SUP> and a start velocity of v
  <SUB>0</SUB> ≈ 590 km s<SUP>-1</SUP>. These findings are consistent
  with the passage of a coronal fast-mode MHD wave, pushing the plasma
  downward and compressing it at the coronal base.

---------------------------------------------------------
Title: Influence of the Ambient Solar Wind Flow on the Propagation
    Behavior of Interplanetary Coronal Mass Ejections
Authors: Temmer, Manuela; Rollett, Tanja; Möstl, Christian; Veronig,
   Astrid M.; Vršnak, Bojan; Odstrčil, Dusan
2011ApJ...743..101T    Altcode: 2011arXiv1110.0827T
  We study three coronal mass ejection (CME)/interplanetary coronal mass
  ejection (ICME) events (2008 June 1-6, 2009 February 13-18, and 2010
  April 3-5) tracked from Sun to 1 AU in remote-sensing observations
  of Solar Terrestrial Relations Observatory Heliospheric Imagers and
  in situ plasma and magnetic field measurements. We focus on the ICME
  propagation in interplanetary (IP) space that is governed by two
  forces: the propelling Lorentz force and the drag force. We address
  the question: which heliospheric distance range does the drag become
  dominant and the CME adjust to the solar wind flow. To this end,
  we analyze speed differences between ICMEs and the ambient solar
  wind flow as a function of distance. The evolution of the ambient
  solar wind flow is derived from ENLIL three-dimensional MHD model
  runs using different solar wind models, namely, Wang-Sheeley-Arge and
  MHD-Around-A-Sphere. Comparing the measured CME kinematics with the
  solar wind models, we find that the CME speed becomes adjusted to the
  solar wind speed at very different heliospheric distances in the three
  events under study: from below 30 R <SUB>⊙</SUB>, to beyond 1 AU,
  depending on the CME and ambient solar wind characteristics. ENLIL can
  be used to derive important information about the overall structure of
  the background solar wind, providing more reliable results during times
  of low solar activity than during times of high solar activity. The
  results from this study enable us to obtain greater insight into the
  forces acting on CMEs over the IP space distance range, which is an
  important prerequisite for predicting their 1 AU transit times.

---------------------------------------------------------
Title: Propagation behavior of interplanetary CMEs: driving versus
    drag force
Authors: Temmer, M.; Rollett, T.; Moestl, C.; Veronig, A. M.;
   Vrsnak, B.
2011AGUFMSH23C1968T    Altcode:
  The evolution of coronal mass ejections (CMEs) is governed by the
  Lorentz and the drag force. Initially, the CME is launched and driven
  by the Lorentz force, whereas the drag force owing to the ambient solar
  wind controls the CME kinematics as it propagates into interplanetary
  (IP) space. The subject of the current study is to infer a heliospheric
  distance at which the drag force starts to prevail over the driving
  force. With the SECCHI instrument suite aboard STEREO, CMEs can be
  observed during their entire propagation all the way from Sun to 1
  AU. In combination with in-situ measurements at 1 AU we are able to
  derive the direction and speed of a CME. This information is used as
  input to derive the kinematical behavior of well observed CME events
  in the IP distance regime, which is subsequently compared to the output
  from ENLIL (NASA/CCMC) MHD model runs for the ambient solar wind flow.

---------------------------------------------------------
Title: Characteristics of Type-II Radio Bursts Associated with Flares
    and CMEs
Authors: Vasanth, V.; Umapathy, S.; Vršnak, Bojan; Anna Lakshmi, M.
2011SoPh..273..143V    Altcode: 2011SoPh..tmp..360V
  We present a statistical study of the characteristics of type-II radio
  bursts observed in the metric (m) and deca-hectometer (DH) wavelength
  range during 1997-2008. The collected events are divided into two
  groups: Group I contains the events of m-type-II bursts with starting
  frequency ≥ 100 MHz, and group II contains the events with starting
  frequency of m-type-II radio bursts &lt; 100 MHz. We have analyzed
  both samples considering three different aspects: i) statistical
  properties of type-II bursts, ii) statistical properties of flares
  and CMEs associated with type-II bursts, and iii) time delays between
  type-II bursts, flares, and CMEs. We find significant differences
  in the properties of m-type-II bursts in duration, bandwidth, drift
  rate, shock speed and delay between m- and DH-type-II bursts. From
  the timing analysis we found that the majority of m-type-II bursts in
  both groups occur during the flare impulsive phase. On the other hand,
  the DH-type-II bursts in both groups occur during the decaying phase
  of the associated flares. Almost all m-DH-type-II bursts are found to
  be associated with CMEs. Our results indicate that there are two kinds
  of shock in which group I (high frequency) m-type-II bursts seem to
  be ignited by flares whereas group II (low frequency) m-type-II bursts
  are CME-driven.

---------------------------------------------------------
Title: Analysis of Characteristic Parameters of Large-scale Coronal
    Waves Observed by the Solar-Terrestrial Relations Observatory/Extreme
    Ultraviolet Imager
Authors: Muhr, N.; Veronig, A. M.; Kienreich, I. W.; Temmer, M.;
   Vršnak, B.
2011ApJ...739...89M    Altcode:
  The kinematical evolution of four extreme ultraviolet waves,
  well observed by the Extreme Ultraviolet Imager on board the
  Solar-Terrestrial Relations Observatory (STEREO), is studied by visually
  tracking wave fronts as well as by a semi-automatized perturbation
  profile method, which leads to results matching each other within
  the error limits. The derived mean velocities of the events under
  study lie in the range of 220-350 km s<SUP>-1</SUP>. The fastest of
  the events (2007 May 19) reveals a significant deceleration of ≈ -
  190 m s<SUP>-2</SUP>, while the others are consistent with a constant
  velocity during wave propagation. The evolution of maximum-intensity
  values reveals initial intensification of 20%-70% and decays to original
  levels within 40-60 minutes, while the widths at half-maximum and
  full-maximum of the perturbation profiles broaden by a factor of two
  to four. The integral below the perturbation profile remains basically
  constant in two cases, while it shows a decrease by a factor of three
  to four in the other two cases. From the peak perturbation amplitudes,
  we estimate the corresponding magnetosonic Mach numbers M <SUB>ms</SUB>,
  which range from 1.08-1.21. The perturbation profiles reveal three
  distinct features behind the propagating wave fronts: coronal dimmings,
  stationary brightenings, and rarefaction regions. All features appear
  after the wave passage and only slowly fade away. Our findings indicate
  that the events under study are weak-shock fast-mode magnetohydrodynamic
  waves initiated by the CME lateral expansion.

---------------------------------------------------------
Title: Solar wind high-speed streams and related geomagnetic activity
    in the declining phase of solar cycle 23
Authors: Verbanac, G.; Vršnak, B.; Živković, S.; Hojsak, T.;
   Veronig, A. M.; Temmer, M.
2011A&A...533A..49V    Altcode:
  Context. Coronal holes (CHs) are the source of high-speed streams
  (HSSs) in the solar wind, whose interaction with the slow solar wind
  creates corotating interaction regions (CIRs) in the heliosphere. <BR
  /> Aims: We investigate the magnetospheric activity caused by CIR/HSS
  structures, focusing on the declining phase of the solar cycle 23
  (years 2005 and 2006), when the occurrence rate of coronal mass
  ejections (CMEs) was low. We aim to (i) perform a systematic analysis
  of the relationship between the CH characteristics, basic parameters of
  HSS/CIRs, and the geomagnetic indices Dst, Ap and AE; (ii) study how the
  magnetospheric/ionospheric current systems behave when influenced by
  HSS/CIR; (iii) investigate if and how the evolution of the background
  solar wind from 2005 to 2006 affected the correlations between CH,
  CIR, and geomagnetic parameters. <BR /> Methods: The cross-correlation
  analysis was applied to the fractional CH area (CH) measured in the
  central meridian distance interval ± 10°, the solar wind velocity (V),
  the interplanetary magnetic field (B), and the geomagnetic indices Dst,
  Ap, and AE. <BR /> Results: The performed analysis shows that Ap and
  AE are better correlated with CH and solar wind parameters than Dst,
  and quantitatively demonstrates that the combination of solar wind
  parameters BV<SUP>2</SUP> and BV plays the central role in the process
  of energy transfer from the solar wind to the magnetosphere. <BR />
  Conclusions: We provide reliable relationships between CH properties,
  HSS/CIR parameters, and geomagnetic indices, which can be used in
  forecasting the geomagnetic activity in periods of low CME activity.

---------------------------------------------------------
Title: Impulsive Acceleration of Coronal Mass Ejections. I. Statistics
    and Coronal Mass Ejection Source Region Characteristics
Authors: Bein, B. M.; Berkebile-Stoiser, S.; Veronig, A. M.; Temmer,
   M.; Muhr, N.; Kienreich, I.; Utz, D.; Vršnak, B.
2011ApJ...738..191B    Altcode: 2011arXiv1108.0561B
  We use high time cadence images acquired by the STEREO EUVI and
  COR instruments to study the evolution of coronal mass ejections
  (CMEs) from their initiation through impulsive acceleration to the
  propagation phase. For a set of 95 CMEs we derived detailed height,
  velocity, and acceleration profiles and statistically analyzed
  characteristic CME parameters: peak acceleration, peak velocity,
  acceleration duration, initiation height, height at peak velocity,
  height at peak acceleration, and size of the CME source region. The CME
  peak accelerations we derived range from 20 to 6800 m s<SUP>-2</SUP>
  and are inversely correlated with the acceleration duration and the
  height at peak acceleration. Seventy-four percent of the events reach
  their peak acceleration at heights below 0.5 R <SUB>sun</SUB>. CMEs that
  originate from compact sources low in the corona are more impulsive and
  reach higher peak accelerations at smaller heights. These findings can
  be explained by the Lorentz force, which drives the CME accelerations
  and decreases with height and CME size.

---------------------------------------------------------
Title: Evolution of Solar and Geomagnetic Activity Indices, and
Their Relationship: 1960 - 2001
Authors: Verbanac, G.; Mandea, M.; Vršnak, B.; Sentic, S.
2011SoPh..271..183V    Altcode: 2011SoPh..tmp..133V; 2011SoPh..tmp..190V; 2011SoPh..tmp..259V
  We employ annually averaged solar and geomagnetic activity indices for
  the period 1960 - 2001 to analyze the relationship between different
  measures of solar activity as well as the relationship between solar
  activity and various aspects of geomagnetic activity. In particular,
  to quantify the solar activity we use the sunspot number R<SUB>s</SUB>,
  group sunspot number R<SUB>g</SUB>, cumulative sunspot area Cum, solar
  radio flux F10.7, and interplanetary magnetic field strength IMF. For
  the geomagnetic activity we employ global indices Ap, Dst and Dcx, as
  well as the regional geomagnetic index RES, specifically estimated for
  the European region. In the paper we present the relative evolution of
  these indices and quantify the correlations between them. Variations
  have been found in: i) time lag between the solar and geomagnetic
  indices; ii) relative amplitude of the geomagnetic and solar activity
  peaks; iii) dual-peak distribution in some of solar and geomagnetic
  indices. The behavior of geomagnetic indices is correlated the best
  with IMF variations. Interestingly, among geomagnetic indices, RES
  shows the highest degree of correlation with solar indices.

---------------------------------------------------------
Title: Analysis of characteristic parameters of large-scale coronal
    waves observed by STEREO/EUVI
Authors: Muhr, N.; Veronig, A. M.; Kienreich, I. W.; Temmer, M.;
   Vrsnak, B.
2011arXiv1107.0921M    Altcode:
  The kinematical evolution of four EUV waves, well observed by the
  Extreme UltraViolet Imager (EUVI) onboard the Solar-Terrestrial
  Relations Observatory (STEREO), is studied by visually tracking the
  wave fronts as well as by a semiautomatized perturbation profile
  method leading to results matching each other within the error
  limits. The derived mean velocities of the events under study lie
  in the range of 220-350 km/s. The fastest of the events (May 19,
  2007) reveals a significant deceleration of \approx -190 m s-2 while
  the others are consistent with a constant velocity during the wave
  propagation. The evolution of the maximum intensity values reveals
  initial intensification by 20 up to 70%, and decays to original
  levels within 40-60 min, while the width at half maximum and full
  maximum of the perturbation profiles are broadening by a factor of
  2 - 4. The integral below the perturbation profile remains basically
  constant in two cases, while it shows a decrease by a factor of 3 -
  4 in the other two cases. From the peak perturbation amplitudes we
  estimate the corresponding magnetosonic Mach numbers Mms which are
  in the range of 1.08-1.21. The perturbation profiles reveal three
  distinct features behind the propagating wave fronts: coronal dimmings,
  stationary brightenings and rarefaction regions. All of them appear
  after the wave passage and are only slowly fading away. Our findings
  indicate that the events under study are weak shock fast-mode MHD
  waves initiated by the CME lateral expansion.

---------------------------------------------------------
Title: Cosmic ray modulation by solar wind disturbances
Authors: Dumbović, M.; Vršnak, B.; Čalogović, J.; Karlica, M.
2011A&A...531A..91D    Altcode:
  <BR /> Aims: We perform a systematic statistical study of the
  relationship between characteristics of solar wind disturbances, caused
  by interplanetary coronal mass ejections and corotating interaction
  regions, and properties of Forbush decreases (FDs). Since the mechanism
  of FDs is still being researched, this analysis should provide a firm
  empirical basis for physical interpretations of the FD phenomenon. <BR
  /> Methods: The analysis is based on the ground-based neutron monitor
  data and the solar wind data recorded by the Advanced Composition
  Explorer, where the disturbances were identified as increases in proton
  speed, magnetic field, and magnetic field fluctuations. We focus on
  the relative timing of FDs, as well as on the correlations between
  various FD and solar wind parameters, paying special attention to
  the statistical significance of the results. <BR /> Results: It was
  found that the onset, the minimum, and the end of FDs are delayed
  after the onset, the maximum, and the end of the magnetic field
  enhancement. The t-test shows that at the 95% significance level the
  average lags have to be longer than 3, 7, and 26 h, respectively. FD
  magnitude (| FD|) is correlated with the magnetic field strength
  (B), magnetic field fluctuations (δB), and speed (v), as well as
  with combined parameters, Bt<SUB>B</SUB>, Bv, vt<SUB>B</SUB>, and
  Bvt<SUB>B</SUB>, where t<SUB>B</SUB> is the duration of the magnetic
  field disturbance. In the |FD|(B) dependence, a "branching" effect
  was observed, i.e., two different trends exist. The analysis of the FD
  duration and recovery period reveals a correlation with the duration of
  the magnetic field enhancement. The strongest correlations are obtained
  for the dependence on combined solar wind parameters of the product
  of the FD duration and magnitude, implying that combined parameters
  are in fact true variables themselves, rather than just a product of
  variables. <BR /> Conclusions: From the time lags we estimate that
  "the penetration depth" in the disturbance, at which FD onset becomes
  recognizable, is on the order of 100 Larmor radii and is comparable
  to a typical shock-sheath dimension. The results for the FD time
  profile indicate "shadow effect" of the solar wind disturbance before
  and after it passes the observer. The importance of reduced parallel
  diffusion during the passage of the disturbance is discussed, along
  with the influence of terrestrial effects on the observed "branching
  effect". <P />Appendices A-C are available in electronic form at <A
  href="http://www.aanda.org">http://www.aanda.org</A>

---------------------------------------------------------
Title: The Drag Based Model of ICME Propagation
Authors: Dumbović, M.; Vršnak, B.; Žic, T.; Vrbanec, D.; Veronig,
   A.; Temmer, M.; Rollett, T.; Moestl, C.; Moon, Y. -J.
2011simi.confR...2D    Altcode:
  One of central issues of space weather is the propagation of
  interplanetary coronal mass ejections (ICMEs). At the heliospheric
  distances beyond R=20 solar radii the "aerodynamic" drag is presumably
  the dominant force governing ICME propagation; therefore, a drag based
  model (DBM) was established, which can be used to forecast the ICME
  arrival at the Earth. <P />First, the model was tested on a sample
  of CMEs by combining remote observations of the CME take-off gained
  by the LASCO onboard SOHO, and in situ measurements from ACE and Wind
  satellites. The results of the DBM were compared to observational data
  and a fairly good agreement of the two was found. The model was then
  tested against STEREO observations. The ICME kinematics was inferred
  from STEREO observations by applying the Harmonic Mean method and
  compared to the DBM results. In this way we were able to reproduce
  the propagation of both slow and fast ICMEs, as well as to identify
  ICME-ICME interactions and a transition from fast-to-slow solar wind
  regimes. Finally, a statistical study was performed, where parameters
  were varied within a model in order to obtain optimal values, for
  which the average difference in the observed and calculated TT is zero
  (O-C=0) and the O-C scatter gets minimum. The source of the scatter
  in O–C values was investigated. <P />The research leading to the
  results presented in this paper has received funding from European
  Community's Seventh Framework Programme (FP7/2007-2013) under grant
  agreement No. 218816.

---------------------------------------------------------
Title: Cosmic Ray Modulation by Solar Wind Disturbances
Authors: Dumbović, M.; Vršnak, B.; Čalogović, J.; Karlica, M.
2011simi.confQ...2D    Altcode:
  Solar wind disturbances (SWDs), namely interplanetary coronal mass
  ejections (ICMEs) and corotating interaction regions (CIRs), cause
  short-term depressions in galactic cosmic ray (GCR) flux. The mechanism
  of this modulation is still a matter of research from observational
  point and theoretical modeling. Since GCR flux reflects solar activity,
  solving this problem represents an important aspect of space weather. <P
  />We analyze the influence of different SWD parameters on the amplitude
  and the duration of the depressions, using ground-based neutron monitor
  data and in situ solar wind data from the ACE satellite. We test
  correlations between GCR depression amplitudes and solar wind speed,
  IMF and IMF fluctuations. Time profiles are also examined. The analysis
  is performed for SWDs in general, ICMEs, CIRs, mixed ICME/CIR events,
  events associated with an interplanetary shock, and events without
  shock. <P />A statistical analysis is also performed regarding the
  delay of the depression after the onset of the IMF increase. We find
  that in the majority of cases the decrease follows the onset in IMF
  increase with an average delay on the order of the typical shock-sheath
  thickness. High correlation between the depression magnitude and the
  increase in IMF fluctuations and strength was found, favoring reduced
  diffusion as a modulation mechanism. Furthermore, the proxies of time
  integrals are found to behave as physical quantities. The differences
  were observed between the data sorted by type (ICME, CIR, and mixed)
  and shock association. Obtained results can be used to test theoretical
  models.

---------------------------------------------------------
Title: Coronal Mass Ejection of 12 June 2010: CME Kinematical
    Parameters
Authors: Maričić, D.; Vršnak, B.; Roša, D.; Hržina, D.;
   Romštajn, I.
2011simi.confQ...5M    Altcode:
  We investigate the initiation and development of the limb coronal mass
  ejection (CME) which launched 12 June 2010, utilizing observations from
  Mauna Loa Solar Observatory (MLSO), Solar and Heliospheric Observatory
  (SOHO), Solar Terrestrial Relations Observatory (STEREO) and Solar
  Dynamic Observatory (SDO). The goal of this study is to investigate
  the new, relatively fast method for determining true geometric and
  kinematical CME parameters from simultaneous observation of CMEs by
  various satellites and ground based MLSO observatory. These parameters
  are direction of CME motion, velocity and acceleration of the different
  parts of CME (the frontal rim, the cavity, and the prominence) and
  CME angular size. Furthermore, we investigate the driving mechanisms
  of CME and infer the magnetic field properties at the onset of the
  instability. To determine the driving mechanism, we quantitatively and
  qualitatively compared the observationally obtained kinematic evolution
  with that predicted by various CME models, mainly based on toroidal
  geometry (cf., Chen, 1989; Vršnak, 1990; Forbes and Isenberg, 1991;
  Amari et al., 2000; Wu et al., 2000; T r k and Kliem, 2005).

---------------------------------------------------------
Title: Comparison between Linear and Quadratic Drag Models for
    ICME Propagation
Authors: Moon, Yong-Jae; Vrsnak, B.; Gopalswamy, N.; Yashiro, S.
2011SPD....42.2318M    Altcode: 2011BAAS..43S.2318M
  In this paper, we have examined a recent issue what kinds of drag
  form (linear or quadratic drag) is proper for interplanetary coronal
  mass ejections (ICMEs). For this work, we have examined well-observed
  LASCO CMEs associated with DH Type II bursts satisfying the following
  conditions: (1) the CMEs speeds are larger than 600 km/s, (2) their
  longitudes are larger than 60 degrees, (3) the numbers of their LASCO
  data points are larger than 6, and (4) their accelerations are smaller
  than -1 m/s<SUP>2</SUP>. We find that their accelerations (Log a) in
  the LASCO field of view has a very good quadratic relationship with
  the CME relative speeds Log (Vcme-400) with the correlation coefficient
  of R=0.83, supporting the quadratic drag force. Another test has been
  made by applying two drag models to two well-observed STEREO/SECCHI
  events. As a result, we found that (1) while two speed profiles are
  well fitted by the quadratic drag model, one speed profile can not be
  fitted by the linear model; (2) while the physical parameters for the
  quadratic model are well consistent with observations, the kinematic
  viscosity for the linear model should be four orders larger than its
  observed value. From this study, we conclude that the quadratic drag
  model for ICME propagation should be proper than the linear drag model.

---------------------------------------------------------
Title: Correlation between CME and Flare Parameters (with and without
    Type II Bursts)
Authors: Shanmugaraju, A.; Moon, Y. -J.; Vršnak, Bojan
2011SoPh..270..273S    Altcode: 2011SoPh..tmp...58S; 2011SoPh..tmp...81S
  CMEs and flares are the two energetic phenomena on the Sun responsible
  for generating shocks. Our main aim is to study the relation between the
  physical properties of CMEs and flares associated with and without type
  II radio bursts. We considered a set of 290 SOHO/LASCO CMEs associated
  with GOES X-ray flares observed during the period from January 1997
  to December 2000. The relationship between the flares and CMEs is
  examined for the two sets i) with metric-type IIs and ii) without
  metric-type IIs. Physical properties such as rise time, duration,
  and strength of the flares and width, speed, and acceleration of CMEs
  are considered. We examined the energy relationship and temporal
  relationship between the CMEs and flares. First, all the events in
  each group were considered, and then the limb events in each group
  were considered separately. While there is a relationship between the
  temporal characteristics of flares and CME properties in the case of
  with-type IIs, it is absent in the case of all without-type IIs. Among
  all the relations studied, the correlation between flare duration
  and CME properties is found to be highly significant compared to the
  other relations. Also, the relationship between flare strength and CME
  speed found in the with-type II events is absent in the case of all
  without-type II events. However, when the limb without-type II events
  (with reduced time window between flare and CME) are studied separately,
  we found the energy relationship and the temporal relationship.

---------------------------------------------------------
Title: Equatorial coronal holes, solar wind high-speed streams,
    and their geoeffectiveness
Authors: Verbanac, G.; Vršnak, B.; Veronig, A.; Temmer, M.
2011A&A...526A..20V    Altcode:
  Context. Solar wind high-speed streams (HSSs), originating in equatorial
  coronal holes (CHs), are the main driver of the geomagnetic activity in
  the late-declining phase of the solar cycle. <BR /> Aims: We analyze
  correlations between CH characteristics, HSSs parameters, and the
  geomagnetic activity indices, to establish empirical relationships
  that would provide forecasting of the solar wind characteristics,
  as well as the effect of HSSs on the geomagnetic activity in periods
  when the effect of coronal mass ejections is low. <BR /> Methods:
  We apply the cross-correlation analysis to the fractional CH area
  (CH) measured between central meridian distances ±10°, solar wind
  parameters (flow velocity V, proton density n, temperature T, and
  the magnetic field B), and the geomagnetic indices Dst and Ap. <BR
  /> Results: The cross-correlation analysis reveals a high degree
  of correlation between all studied parameters. In particular, we
  show that the Ap index is considerably more sensitive to HSS and CH
  characteristics than Dst. The Ap and Dst indices are most tightly
  correlated with the solar wind parameter BV<SUP>2</SUP>. <BR />
  Conclusions: From the point of view of space weather, the most
  important result is that the established empirical relationships
  provide a few-days-in-advance forecasting of the HSS characteristics
  and the related geomagnetic activity at the six-hour resolution. <P
  />Appendices, Figs. 9-14, and table 4 are only available in electronic
  form at <A href="http://www.aanda.org">http://www.aanda.org</A>

---------------------------------------------------------
Title: Case Study of Four Homologous Large-scale Coronal Waves
    Observed on 2010 April 28 and 29
Authors: Kienreich, I. W.; Veronig, A. M.; Muhr, N.; Temmer, M.;
   Vršnak, B.; Nitta, N.
2011ApJ...727L..43K    Altcode: 2011arXiv1101.5232K
  On 2010 April 28 and 29, the Solar TErrestrial Relations Observatory
  B/Extreme Ultraviolet Imager observed four homologous large-scale
  coronal waves, the so-called EIT-waves, within 8 hr. All waves emerged
  from the same source active region, were accompanied by weak flares and
  faint coronal mass ejections, and propagated into the same direction
  at constant velocities in the range of ~220-340 km s<SUP>-1</SUP>. The
  last of these four coronal wave events was the strongest and fastest,
  with a velocity of 337 ± 31 km s<SUP>-1</SUP> and a peak perturbation
  amplitude of ~1.24, corresponding to a magnetosonic Mach number of M
  <SUB>ms</SUB> ~ 1.09. The magnetosonic Mach numbers and velocities of
  the four waves are distinctly correlated, suggestive of the nonlinear
  fast-mode magnetosonic wave nature of the events. We also found a
  correlation between the magnetic energy buildup times and the velocity
  and magnetosonic Mach number.

---------------------------------------------------------
Title: Inventorying the Solar System with LSST
Authors: Jones, R. Lynne; Brown, M. E.; Abel, P. A.; Chesley, S. R.;
   Durech, J.; Fernandez, Y. R.; Harris, A. W.; Holman, M. J.; Ivezic,
   Z.; Jedicke, R.; Kaasalainen, M.; Kaib, N. A.; Knevezic, Z.; Milani,
   A.; Park, A.; Ragozzine, D.; Ridgway, S. T.; Trilling, D. E.; Vrsnak,
   B.; LSST Solar System Science Collaboration
2011AAS...21725210J    Altcode: 2011BAAS...4325210J
  Near the ecliptic, LSST is expected to detect approximately 4000
  moving objects per 9.6 square degree field of view. Each pointing
  (with mag limits r 24.5) will be revisited within 30-45 minutes,
  several times per month. Automated software will provide the means
  to link these individual detections into orbits. The result will be
  publicly available catalogs of hundreds of thousands of NEOs and Jupiter
  Trojans, millions of asteroids, tens of thousands of TNOs, as well as
  thousands of other objects such as comets and irregular satellites of
  the major planets. These catalogs will contain final orbits as well
  as the individual (multi-color) observations, calibrated to high
  precisision in astrometry ( 50 mas) and photometry ( 0.01 mag). <P
  />With these large datasets, LSST will provide new insights into
  links between populations of moving objects, such as the relationship
  between Main Belt asteroids and NEOs. Models of solar system evolution,
  such as the Nice model, can be tested against an order of magnitude
  larger statistical sample, providing much stronger constraints than
  are currently possible. With high accuracy multi-color photometry,
  lightcurves and colors will be determined for a significant fraction
  of the objects detected. Using sparse lightcurve inversion, spin state
  and shape models will be derived for tens of thousands of main belt
  asteroids. Derivation of proper elements for Main Belt asteroids
  will greatly enlarge existing asteroid families, particularly at
  smaller sizes, and precise color information will facilitate further
  division. More unpredictable discoveries, such as the potential for
  observing a real-time collision, could lead to new insights into
  physical properties, the size distribution at very small diameters,
  the orbital evolution of asteroids, or the discovery of possible space
  mission targets.

---------------------------------------------------------
Title: Application of data assimilation to solar wind forecasting
    models
Authors: Innocenti, M.; Lapenta, G.; Vrsnak, B.; Temmer, M.; Veronig,
   A.; Bettarini, L.; Lee, E.; Markidis, S.; Skender, M.; Crespon, F.;
   Skandrani, C.; Soteria Space-Weather Forecast; Data Assimilation Team
2010AGUFMSM54A..08I    Altcode:
  Data Assimilation through Kalman filtering [1,2] is a powerful
  statistical tool which allows to combine modeling and observations
  to increase the degree of knowledge of a given system. We apply this
  technique to the forecast of solar wind parameters (proton speed, proton
  temperature, absolute value of the magnetic field and proton density) at
  1 AU, using the model described in [3] and ACE data as observations. The
  model, which relies on GOES 12 observations of the percentage of the
  meridional slice of the sun covered by coronal holes, grants 1-day and
  6-hours in advance forecasts of the aforementioned quantities in quiet
  times (CMEs are not taken into account) during the declining phase
  of the solar cycle and is tailored for specific time intervals. We
  show that the application of data assimilation generally improves
  the quality of the forecasts during quiet times and, more notably,
  extends the periods of applicability of the model, which can now provide
  reliable forecasts also in presence of CMEs and for periods other than
  the ones it was designed for. Acknowledgement: The research leading
  to these results has received funding from the European Commission’s
  Seventh Framework Programme (FP7/2007-2013) under the grant agreement
  N. 218816 (SOTERIA project: http://www.soteria-space.eu). References:
  [1] R. Kalman, J. Basic Eng. 82, 35 (1960); [2] G. Welch and G. Bishop,
  Technical Report TR 95-041, University of North Carolina, Department
  of Computer Science (2001); [3] B. Vrsnak, M. Temmer, and A. Veronig,
  Solar Phys. 240, 315 (2007).

---------------------------------------------------------
Title: On the Origin of the Solar Moreton Wave of 2006 December 6
Authors: Balasubramaniam, K. S.; Cliver, E. W.; Pevtsov, A.; Temmer,
   M.; Henry, T. W.; Hudson, H. S.; Imada, S.; Ling, A. G.; Moore, R. L.;
   Muhr, N.; Neidig, D. F.; Petrie, G. J. D.; Veronig, A. M.; Vršnak,
   B.; White, S. M.
2010ApJ...723..587B    Altcode:
  We analyzed ground- and space-based observations of the eruptive flare
  (3B/X6.5) and associated Moreton wave (~850 km s<SUP>-1</SUP> ~270°
  azimuthal span) of 2006 December 6 to determine the wave driver—either
  flare pressure pulse (blast) or coronal mass ejection (CME). Kinematic
  analysis favors a CME driver of the wave, despite key gaps in coronal
  data. The CME scenario has a less constrained/smoother velocity versus
  time profile than is the case for the flare hypothesis and requires an
  acceleration rate more in accord with observations. The CME picture is
  based, in part, on the assumption that a strong and impulsive magnetic
  field change observed by a GONG magnetograph during the rapid rise phase
  of the flare corresponds to the main acceleration phase of the CME. The
  Moreton wave evolution tracks the inferred eruption of an extended
  coronal arcade, overlying a region of weak magnetic field to the west
  of the principal flare in NOAA active region 10930. Observations of
  Hα foot point brightenings, disturbance contours in off-band Hα
  images, and He I 10830 Å flare ribbons trace the eruption from 18:42
  to 18:44 UT as it progressed southwest along the arcade. Hinode EIS
  observations show strong blueshifts at foot points of this arcade
  during the post-eruption phase, indicating mass outflow. At 18:45
  UT, the Moreton wave exhibited two separate arcs (one off each flank
  of the tip of the arcade) that merged and coalesced by 18:47 UT to
  form a single smooth wave front, having its maximum amplitude in
  the southwest direction. We suggest that the erupting arcade (i.e.,
  CME) expanded laterally to drive a coronal shock responsible for the
  Moreton wave. We attribute a darkening in Hα from a region underlying
  the arcade to absorption by faint unresolved post-eruption loops.

---------------------------------------------------------
Title: Modeling UV and X-ray Emission in a Post-coronal Mass Ejection
    Current Sheet
Authors: Ko, Yuan-Kuen; Raymond, John C.; Vršnak, Bojan; Vujić, Eugen
2010ApJ...722..625K    Altcode: 2010arXiv1008.1732K
  A post-coronal mass ejection (CME) current sheet (CS) is a
  common feature developed behind an erupting flux rope in CME
  models. Observationally, white light observations have recorded
  many occurrences of a thin ray appearing behind a CME eruption
  that closely resembles a post-CME CS in its spatial correspondence
  and morphology. UV and X-ray observations further strengthen this
  interpretation by the observations of high-temperature emission at
  locations consistent with model predictions. The next question then
  becomes whether the properties inside a post-CME CS predicted by a
  model agree with observed properties. In this work, we assume that
  the post-CME CS is a consequence of Petschek-like reconnection and
  that the observed ray-like structure is bounded by a pair of slow mode
  shocks developed from the reconnection site. We perform time-dependent
  ionization calculations and model the UV line emission. We find that
  such a model is consistent with SOHO/UVCS observations of the post-CME
  CS. The change of Fe XVIII emission in one event implies an inflow
  speed of ~10 km s<SUP>-1</SUP> and a corresponding reconnection rate
  of M<SUB>A</SUB> ~ 0.01. We calculate the expected X-ray emission for
  comparison with X-ray observations by Hinode/XRT, as well as the ionic
  charge states as would be measured in situ at 1 AU. We find that the
  predicted count rate for Hinode/XRT agrees with what was observed in
  a post-CME CS on 2008 April 9, and the predicted ionic charge states
  are consistent with high ionization states commonly measured in the
  interplanetary CMEs. The model results depend strongly on the physical
  parameters in the ambient corona, namely the coronal magnetic field,
  the electron density, and temperature during the CME event. It is
  crucial to obtain these ambient coronal parameters and as many facets
  of the CS properties as possible by observational means so that the
  post-CME CS models can be scrutinized more effectively.

---------------------------------------------------------
Title: Type-II Bursts in Meter and Deca - Hectometer Wavelengths
and Their Relation to Flares and CMEs: II
Authors: Prakash, O.; Umapathy, S.; Shanmugaraju, A.; Pappa kalaivani,
   P.; Vršnak, Bojan
2010SoPh..266..135P    Altcode: 2010SoPh..tmp..148P
  A study of the relationship between 38 type-II bursts recorded in meter
  and deca-hectometer (hereinafter m and DH) wavelength range and the
  associated flares and CMEs observed during the years 2000 - 2005 was
  carried out by Prakash et al. (2009). These events were divided into two
  classes: i) Class I, representing events where DH-type-II bursts are not
  a continuation of m-type-II bursts and ii) Class II, where DH-type-II
  bursts are a continuation of m-type-II bursts. In the present work,
  we extend the analysis of this sample of 38 events in three different
  steps: i) statistical properties of m- and DH-type-II bursts; ii)
  analysis of time lags between onsets of flares and CMEs associated with
  type-II bursts; and iii) statistical properties and relation between
  flares and CMEs of Class I and Class II events. We found a significant
  difference between the properties of m- and DH-type-II bursts of Class
  I and Class II events. For example, there are significant differences
  in starting and ending frequencies, bandwidth and speed. From the
  time delay analysis, we found the following. i) In 64% of Class I
  events, flares start after the onset of CMEs and the remaining 36%
  of flares start before the onset of CMEs. On the other hand, in the
  case of Class II events, the values are 83% and 17%, respectively. ii)
  The difference between the mean values of delay between flare start
  and DH start has high statistical significance (probability P of null
  hypothesis &lt;1%). The time delays between the start of m-type-II burst
  and the CME onset are considerably larger for Class I events (P=7%)
  than Class II events. iii) There are notable differences in: (a) delay
  between the flare and CME onset times (P&lt;1%); (b) flare rise time of
  Class I and Class II events (P&lt;5%). iv) While the flare rise time is
  well correlated with the lag between the flare start and the CME onset
  in Class I events, there is no such correlation for Class II events.

---------------------------------------------------------
Title: Observations of Chromospheric Flare Re-brightenings
Authors: Miklenic, C. H.; Veronig, A. M.; Vršnak, B.; Bárta, M.
2010ApJ...719.1750M    Altcode:
  We investigate an active region that produced three C-class flares
  and one M-class flare within 2.5 hr. The morphology and location of
  the C-flares indicate that these events constitute a set of homologous
  flares. Radio observations indicate the occurrence of a downward-moving
  plasmoid during the impulsive phase of the M flare. We use TRACE
  1700 Å filtergrams and SOHO Michelson Doppler Imager magnetograms
  to examine the character of the UV brightenings; i.e., we search
  for re-brightenings of former flare areas both across the series of
  events and within one and the same event. We find that essentially the
  same footpoints re-brighten in each C flare. Based on the progression
  of both the derived magnetic flux change rate and the observed Radio
  Solar Telescope Network microwave emission, we speculate about a further
  re-brightening during the decay phase of the M flare as a further member
  of the series of homologous flares. We conclude that the "postflare"
  field is driven to repeated eruption by continuous, shear-increasing,
  horizontal, photospheric flows, as one end of the involved magnetic
  arcade is anchored in the penumbra of a large sunspot. The observed
  motion pattern of the UV kernels indicates that the arcade evolves
  during the series of events from a both highly sheared and heavily
  entangled state to a still sheared but more organized state.

---------------------------------------------------------
Title: Multiwavelength Imaging and Spectroscopy of Chromospheric
    Evaporation in an M-class Solar Flare
Authors: Veronig, A. M.; Rybák, J.; Gömöry, P.; Berkebile-Stoiser,
   S.; Temmer, M.; Otruba, W.; Vršnak, B.; Pötzi, W.; Baumgartner, D.
2010ApJ...719..655V    Altcode: 2010arXiv1007.0930V
  We study spectroscopic observations of chromospheric evaporation mass
  flows in comparison with the energy input by electron beams derived
  from hard X-ray (HXR) data for the white-light M2.5 flare of 2006 July
  6. The event was captured in high-cadence spectroscopic observing mode
  by SOHO/CDS combined with high-cadence imaging at various wavelengths
  in the visible, extreme ultraviolet, and X-ray domain during the joint
  observing campaign JOP171. During the flare peak, we observe downflows
  in the He I and O V lines formed in the chromosphere and transition
  region, respectively, and simultaneous upflows in the hot coronal
  Si XII line. The energy deposition rate by electron beams derived
  from RHESSI HXR observations is suggestive of explosive chromospheric
  evaporation, consistent with the observed plasma motions. However, for
  a later distinct X-ray burst, where the site of the strongest energy
  deposition is exactly located on the Coronal Diagnostics Spectrometer
  (CDS) slit, the situation is intriguing. The O V transition region
  line spectra show the evolution of double components, indicative of
  the superposition of a stationary plasma volume and upflowing plasma
  elements with high velocities (up to 280 km s<SUP>-1</SUP>) in single
  CDS pixels on the flare ribbon. However, the energy input by electrons
  during this period is too small to drive explosive chromospheric
  evaporation. These unexpected findings indicate that the flaring
  transition region is much more dynamic, complex, and fine structured
  than is captured in single-loop hydrodynamic simulations.

---------------------------------------------------------
Title: Coronal Shocks Associated with Impulsive and Decaying Phases
    of Solar Flares
Authors: Suresh, K.; Umapathy, S.; Shanmugaraju, A.; Vršnak, B.
2010SoPh..264..353S    Altcode: 2010SoPh..tmp..108S
  We have analyzed a set of 147 metric Type II radio bursts observed by
  Culgoora radio spectrograph from November 1997 to December 2006. These
  events were divided into two sets: The first subset contains Type
  II events that started during the impulsive phase of the associated
  solar flares and the second subset contains those starting during
  the decaying phase of flares. Our main aim is to differentiate the
  metric Type IIs, flares and coronal mass ejections (CMEs) of these
  two subsets. It is found that while Type II burst characteristics
  of both subsets are very similar, there are significant differences
  between flare and CME properties for these two subsets. Considering
  all analyzed relationships between the characteristics of Type IIs,
  flares and CMEs in these two Type II subsets, we conclude that most of
  the coronal shocks causing metric Type II bursts are driven by CMEs,
  but that a fraction of events are probably ignited by solar flares.

---------------------------------------------------------
Title: Origin of Coronal Shock Waves Associated with Slow Coronal
    Mass Ejections
Authors: Magdalenić, J.; Marqué, C.; Zhukov, A. N.; Vršnak, B.;
   Žic, T.
2010ApJ...718..266M    Altcode:
  We present a multiwavelength study of five coronal mass ejection/flare
  events (CME/flare) and associated coronal shock waves manifested as type
  II radio bursts. The study is focused on the events in which the flare
  energy release, and not the associated CME, is the most probable source
  of the shock wave. Therefore, we selected events associated with rather
  slow CMEs (reported mean velocity below 500 km s<SUP>-1</SUP>). To
  ensure minimal projection effects, only events related to flares
  situated close to the solar limb were included in the study. We used
  radio dynamic spectra, positions of radio sources observed by the
  Nançay Radioheliograph, GOES soft X-ray flux measurements, Large Angle
  Spectroscopic Coronagraph, and Extreme-ultraviolet Imaging Telescope
  observations. The kinematics of the shock wave signatures, type II
  radio bursts, were analyzed and compared with the flare evolution
  and the CME kinematics. We found that the velocities of the shock
  waves were significantly higher, up to one order of magnitude, than
  the contemporaneous CME velocities. On the other hand, shock waves
  were closely temporally associated with the flare energy release that
  was very impulsive in all events. This suggests that the impulsive
  increase of the pressure in the flare was the source of the shock
  wave. In four events the shock wave was most probably flare-generated,
  and in one event results were inconclusive due to a very close temporal
  synchronization of the CME, flare, and shock.

---------------------------------------------------------
Title: Investigations of the sensitivity of a coronal mass ejection
    model (ENLIL) to solar input parameters
Authors: Falkenberg, T. V.; Vršnak, B.; Taktakishvili, A.; Odstrcil,
   D.; MacNeice, P.; Hesse, M.
2010SpWea...8.6004F    Altcode:
  Understanding space weather is not only important for satellite
  operations and human exploration of the solar system but also to
  phenomena here on Earth that may potentially disturb and disrupt
  electrical signals. Some of the most violent space weather effects
  are caused by coronal mass ejections (CMEs), but in order to predict
  the caused effects, we need to be able to model their propagation
  from their origin in the solar corona to the point of interest, e.g.,
  Earth. Many such models exist, but to understand the models in detail
  we must understand the primary input parameters. Here we investigate
  the parameter space of the ENLILv2.5b model using the CME event of 25
  July 2004. ENLIL is a time-dependent 3-D MHD model that can simulate
  the propagation of cone-shaped interplanetary coronal mass ejections
  (ICMEs) through the solar system. Excepting the cone parameters
  (radius, position, and initial velocity), all remaining parameters are
  varied, resulting in more than 20 runs investigated here. The output
  parameters considered are velocity, density, magnetic field strength,
  and temperature. We find that the largest effects on the model output
  are the input parameters of upper limit for ambient solar wind velocity,
  CME density, and elongation factor, regardless of whether one's main
  interest is arrival time, signal shape, or signal amplitude of the
  ICME. We find that though ENLILv2.5b currently does not include the
  magnetic cloud of the ICME, it replicates the signal at L1 well in the
  studied event. The arrival time difference between satellite data and
  the ENLILv2.5b baseline run of this study is less than 30 min.

---------------------------------------------------------
Title: First Observations of a Dome-shaped Large-scale Coronal
    Extreme-ultraviolet Wave
Authors: Veronig, A. M.; Muhr, N.; Kienreich, I. W.; Temmer, M.;
   Vršnak, B.
2010ApJ...716L..57V    Altcode: 2010arXiv1005.2060V
  We present first observations of a dome-shaped large-scale
  extreme-ultraviolet coronal wave, recorded by the Extreme Ultraviolet
  Imager instrument on board STEREO-B on 2010 January 17. The main
  arguments that the observed structure is the wave dome (and not the
  coronal mass ejection, CME) are (1) the spherical form and sharpness of
  the dome's outer edge and the erupting CME loops observed inside the
  dome; (2) the low-coronal wave signatures above the limb perfectly
  connecting to the on-disk signatures of the wave; (3) the lateral
  extent of the expanding dome which is much larger than that of the
  coronal dimming; and (4) the associated high-frequency type II burst
  indicating shock formation low in the corona. The velocity of the upward
  expansion of the wave dome (v ~ 650 km s<SUP>-1</SUP>) is larger than
  that of the lateral expansion of the wave (v ~ 280 km s<SUP>-1</SUP>),
  indicating that the upward dome expansion is driven all the time,
  and thus depends on the CME speed, whereas in the lateral direction it
  is freely propagating after the CME lateral expansion stops. We also
  examine the evolution of the perturbation characteristics: first the
  perturbation profile steepens and the amplitude increases. Thereafter,
  the amplitude decreases with r <SUP>-2.5 ± 0.3</SUP>, the width
  broadens, and the integral below the perturbation remains constant. Our
  findings are consistent with the spherical expansion and decay of a
  weakly shocked fast-mode MHD wave.

---------------------------------------------------------
Title: Four decades of geomagnetic and solar activity: 1960-2001
Authors: Verbanac, Giuli; Vršnak, Bojan; Temmer, Manuela; Mandea,
   Mioara; Korte, Monika
2010JASTP..72..607V    Altcode:
  We analyze the relationship between some space weather indices (Dst,
  Ap, F10.7) and geomagnetic effects on the regional (European) scale,
  over the period 1960-2001. The remaining external field signal (RES)
  detected in the Northward magnetic component of the European observatory
  annual means are used as an indicator of the regional geomagnetic
  activity. Relationship RES-F10.7 suggests correction factors for getting
  the geomagnetic annual means of the Northern component less affected by
  the external sources. We have found some time lags among investigated
  parameters. These delays may suggest that the Ap responds to the solar
  activity in a differently than Dst and RES, Ap being more sensitive
  to the high-speed streams (HSS) and the Alfvenic waves present in HSS,
  while Dst and RES being more influenced by the coronal mass ejections
  activity (CME).

---------------------------------------------------------
Title: Combined STEREO/RHESSI Study of Coronal Mass Ejection
    Acceleration and Particle Acceleration in Solar Flares
Authors: Temmer, M.; Veronig, A. M.; Kontar, E. P.; Krucker, S.;
   Vršnak, B.
2010ApJ...712.1410T    Altcode: 2010arXiv1002.3080T
  Using the potential of two unprecedented missions, Solar Terrestrial
  Relations Observatory (STEREO) and Reuven Ramaty High-Energy Solar
  Spectroscopic Imager (RHESSI), we study three well-observed fast coronal
  mass ejections (CMEs) that occurred close to the limb together with
  their associated high-energy flare emissions in terms of RHESSI hard
  X-ray (HXR) spectra and flux evolution. From STEREO/EUVI and STEREO/COR1
  data, the full CME kinematics of the impulsive acceleration phase up to
  ~4 R <SUB>sun</SUB> is measured with a high time cadence of &lt;=2.5
  minutes. For deriving CME velocity and acceleration, we apply and
  test a new algorithm based on regularization methods. The CME maximum
  acceleration is achieved at heights h &lt;= 0.4 R <SUB>sun</SUB>,
  and the peak velocity at h &lt;= 2.1 R <SUB>sun</SUB> (in one case,
  as small as 0.5 R <SUB>sun</SUB>). We find that the CME acceleration
  profile and the flare energy release as evidenced in the RHESSI HXR flux
  evolve in a synchronized manner. These results support the "standard"
  flare/CME model which is characterized by a feedback relationship
  between the large-scale CME acceleration process and the energy release
  in the associated flare.

---------------------------------------------------------
Title: The role of aerodynamic drag in propagation of interplanetary
    coronal mass ejections
Authors: Vršnak, B.; Žic, T.; Falkenberg, T. V.; Möstl, C.;
   Vennerstrom, S.; Vrbanec, D.
2010A&A...512A..43V    Altcode:
  Context. The propagation of interplanetary coronal mass ejections
  (ICMEs) and the forecast of their arrival on Earth is one of the
  central issues of space weather studies. <BR /> Aims: We investigate
  to which degree various ICME parameters (mass, size, take-off speed)
  and the ambient solar-wind parameters (density and velocity) affect
  the ICME Sun-Earth transit time. <BR /> Methods: We study solutions of
  a drag-based equation of motion by systematically varying the input
  parameters. The analysis is focused on ICME transit times and 1 AU
  velocities. <BR /> Results: The model results reveal that wide ICMEs
  of low masses adjust to the solar-wind speed already close to the
  sun, so the transit time is determined primarily by the solar-wind
  speed. The shortest transit times and accordingly the highest 1 AU
  velocities are related to narrow and massive ICMEs (i.e. high-density
  eruptions) propagating in high-speed solar wind streams. We apply the
  model to the Sun-Earth event associated with the CME of 25 July 2004
  and compare the results with the outcome of the numerical MHD modeling.

---------------------------------------------------------
Title: Quasi-Periodic Oscillations in Lasco Coronal Mass Ejection
    Speeds
Authors: Shanmugaraju, A.; Moon, Y. -J.; Cho, K. -S.; Bong, S. C.;
   Gopalswamy, N.; Akiyama, S.; Yashiro, S.; Umapathy, S.; Vrsnak, B.
2010ApJ...708..450S    Altcode:
  Quasi-periodic oscillations in the speed profile of coronal mass
  ejections (CMEs) in the radial distance range 2-30 solar radii are
  studied. We considered the height-time data of the 307 CMEs recorded
  by the Large Angle and Spectrometric Coronagraph (LASCO) during 2005
  January-March. In order to study the speed-distance profile of the CMEs,
  we have used only 116 events for which there are at least 10 height-time
  measurements made in the LASCO field of view. The instantaneous CME
  speed is estimated using a pair of height-time data points, providing
  the speed-distance profile. We found quasi-periodic patterns in at
  least 15 speed-distance profiles, where the speed amplitudes are larger
  than the speed errors. For these events we have determined the speed
  amplitude and period of oscillations. The periods of quasi-periodic
  oscillations are found in the range 48-240 minutes, tending to
  increase with height. The oscillations have similar properties as
  those reported by Krall et al., who interpreted them in terms of the
  flux-rope model. The nature of forces responsible for the motion of
  CMEs and their oscillations are discussed.

---------------------------------------------------------
Title: Inventorying the Solar System with LSST
Authors: Jones, R. Lynne; Chesley, S. R.; Abell, P. A.; Brown, M. E.;
   Durech, J.; Fernandez, Y. R.; Harris, A. W.; Holman, M. J.; Ivezic,
   Z.; Jedicke, R.; Kaasaleinen, M.; Kaib, N. A.; Knevezic, Z.; Milani,
   A.; Parker, A.; Ridgway, S. T.; Trilling, D. E.; Vrsnak, B.; LSST
   Solar System Science Collaboration
2010AAS...21540107J    Altcode: 2010BAAS...42..218J
  LSST's extremely wide sky coverage (&gt;30,000 square degrees),
  coupled with a faint limiting magnitude (r 24.7 per image), and a
  rapid observational cadence -- each field is observed twice per night,
  4-5 times each month -- result in a survey telescope with powerful
  potential for detecting small moving objects. Near the ecliptic,
  LSST is expected to detect approximately 4000 moving objects per 9.6
  square degree field of view; automated software will provide the
  means to link these individual detections into orbits. The result
  will be catalogs of hundreds of thousands of NEOs and Jupiter
  Trojans, millions of asteroids, tens of thousands of TNOs, and
  thousands of other objects such as comets and irregular satellites
  of the major planets. These catalogs will be publicly available,
  both final orbits and the underlying multi-color observations, with
  highly accurate measurements in astrometry ( 50 mas) and photometry (
  0.01-0.02 mag). <P />With these large datasets, LSST will provide new
  insights into links between populations of moving objects, such as the
  relationship between Main Belt asteroids and NEOs. Models of solar
  system evolution, such as the Nice model, can be tested against an
  order of magnitude larger statistical sample, providing much stronger
  constraints than are currently possible. Detection of populations of
  objects beyond Neptune at a wide range of ecliptic latitudes as well as
  a well-characterized measurement of cometary populations will permit
  measurements of the nature of the inner and outer Oort cloud. Using
  high accuracy multicolor photometry, lightcurves and colors will be
  determined for a significant fraction of the objects detected. Through
  sparse lightcurve inversion, spin state and shape models will be
  derived for tens of thousands of main belt asteroids. Derivation of
  proper elements for Main Belt asteroids will greatly enlarge existing
  asteroid families, particularly at smaller sizes, and precise color
  information will facilitate further divisions.

---------------------------------------------------------
Title: Analysis of a Global Moreton Wave Observed on 2003 October 28
Authors: Muhr, N.; Vršnak, B.; Temmer, M.; Veronig, A. M.;
   Magdalenić, J.
2010ApJ...708.1639M    Altcode: 2009arXiv0911.4405M
  We study the well-pronounced Moreton wave that occurred in association
  with the X17.2 flare/CME event of 2003 October 28. This Moreton wave is
  striking for its global propagation and two separate wave centers, which
  implies that two waves were launched simultaneously. The mean velocity
  of the Moreton wave, tracked within different sectors of propagation
  direction, lies in the range of v ≈ 900-1100 km s<SUP>-1</SUP> with
  two sectors showing wave deceleration. The perturbation profile analysis
  of the wave indicates amplitude growth followed by amplitude weakening
  and broadening of the perturbation profile, which is consistent with
  a disturbance first driven and then evolving into a freely propagating
  wave. The Extreme-Ultraviolet Imaging Telescope wave front is found to
  lie on the same kinematical curve as the Moreton wave fronts indicating
  that both are different signatures of the same physical process. Bipolar
  coronal dimmings are observed on the same opposite east-west edges of
  the active region as the Moreton wave ignition centers. The radio type
  II source, which is cospatially located with the first wave front,
  indicates that the wave was launched from an extended source region
  (gsim60 Mm). These findings suggest that the Moreton wave is initiated
  by the coronal mass ejection expanding flanks.

---------------------------------------------------------
Title: Flare-generated coronal shock on 14 November 2005
Authors: Magdalenic, Jasmina; Marque, Christophe; Zhukov, Andrei;
   Veronig, Astrid; Vrsnak, Bojan
2010cosp...38.1798M    Altcode: 2010cosp.meet.1798M
  Origin of coronal shock waves is still not completely understood. Since
  the flare impulsive phase and the acceleration phase of a CME are
  usually well synchronized, it is difficult to give a conclusive
  answer on the shock wave origin in flare/CME events. We present
  multiwave-length study of a shock wave associated with the flare event
  recorded on 14 November 2005. The evolution of the shock wave signature
  -type II radio burst -is analysed using dynamic spectra recorded by the
  Green Bank Solar Radio Bursts Spectrometer and Nançay Radioheliograph
  imaging. The observations of the plasma dynamics in the low and high
  corona were provided by EIT and LASCO instruments onboard SOHO. The
  strong type II emission starts at unusually high frequency of 700
  MHz. The obtained values for the shock velocity, Alfven velocity and
  Alfven Mach number are in the range of typical shock parameters. The
  shock wave was closely associated with the impulsive phase of the
  compact M3.9 flare in the NOAA AR 10822 (located at S06E60). The
  short impulsive phase of the flare (4 minutes), suggests that a
  strong pressure pulse was ignited by the flare. Additionally, RHESSI
  observations show compact event of a rather high density and high
  temperature which gives indication of a strong, impulsive increase
  of pressure in the small flare loop. SOHO/LASCO observations do not
  show any CME associated with this event. Since the active region
  is rather close to the limb, the possibility that the corresponding
  CME is not observed due to the unfavorable geometry is unlikely. We
  therefore conclude that the shock wave recorded on 14 November 2005
  was a blast wave launched by the impulsive energy release in the course
  of the flare.

---------------------------------------------------------
Title: Study of the kinematics and driver of the global Moreton wave
    observed on 2003 October 28
Authors: Muhr, Mmag. Nicole; Vrsnak, Bojan; Temmer, Manuela; Veronig,
   Astrid; Magdalenic, Jasmina
2010cosp...38.1844M    Altcode: 2010cosp.meet.1844M
  We analyze the evolution and kinematics of the fast, globally
  propagating Moreton wave of 2003 October 28 associated with the extreme
  X17.2 solar flare/CME event. This Moreton wave is distinct due to its
  strengths and azimuthal span of span 360. We study the wave kinematics
  in different propagation directions, and compare it with the following
  associated phenomena: EIT wave, coronal dimmings, fast halo CME, flare,
  and type II burst. The sectoral analysis yield mean velocity values
  in the range 900-1000 km/s; two sectors show wave deceleration. The
  perturbation profile evolution indicates an amplitude growth followed
  by amplitude weakening and broadening, which is consistent with a
  disturbance first driven and then evolving into a freely propagating
  wave. We find two `'radiant points" for the Moreton wave fronts on
  opposite east-west edges of the source region, roughly co-spatial with
  the bipolar coronal dimming. The co-spatiality of the associated radio
  type II burst source and the first Moreton wave fronts indicate that
  the wave was launched from an extended region. These findings indicate
  that the wave is initiated by the CME expanding flanks.

---------------------------------------------------------
Title: LSST Science Book, Version 2.0
Authors: LSST Science Collaboration; Abell, Paul A.; Allison, Julius;
   Anderson, Scott F.; Andrew, John R.; Angel, J. Roger P.; Armus, Lee;
   Arnett, David; Asztalos, S. J.; Axelrod, Tim S.; Bailey, Stephen;
   Ballantyne, D. R.; Bankert, Justin R.; Barkhouse, Wayne A.; Barr,
   Jeffrey D.; Barrientos, L. Felipe; Barth, Aaron J.; Bartlett, James
   G.; Becker, Andrew C.; Becla, Jacek; Beers, Timothy C.; Bernstein,
   Joseph P.; Biswas, Rahul; Blanton, Michael R.; Bloom, Joshua S.;
   Bochanski, John J.; Boeshaar, Pat; Borne, Kirk D.; Bradac, Marusa;
   Brandt, W. N.; Bridge, Carrie R.; Brown, Michael E.; Brunner, Robert
   J.; Bullock, James S.; Burgasser, Adam J.; Burge, James H.; Burke,
   David L.; Cargile, Phillip A.; Chandrasekharan, Srinivasan; Chartas,
   George; Chesley, Steven R.; Chu, You-Hua; Cinabro, David; Claire,
   Mark W.; Claver, Charles F.; Clowe, Douglas; Connolly, A. J.; Cook,
   Kem H.; Cooke, Jeff; Cooray, Asantha; Covey, Kevin R.; Culliton,
   Christopher S.; de Jong, Roelof; de Vries, Willem H.; Debattista,
   Victor P.; Delgado, Francisco; Dell'Antonio, Ian P.; Dhital, Saurav;
   Di Stefano, Rosanne; Dickinson, Mark; Dilday, Benjamin; Djorgovski,
   S. G.; Dobler, Gregory; Donalek, Ciro; Dubois-Felsmann, Gregory;
   Durech, Josef; Eliasdottir, Ardis; Eracleous, Michael; Eyer, Laurent;
   Falco, Emilio E.; Fan, Xiaohui; Fassnacht, Christopher D.; Ferguson,
   Harry C.; Fernandez, Yanga R.; Fields, Brian D.; Finkbeiner, Douglas;
   Figueroa, Eduardo E.; Fox, Derek B.; Francke, Harold; Frank, James
   S.; Frieman, Josh; Fromenteau, Sebastien; Furqan, Muhammad; Galaz,
   Gaspar; Gal-Yam, A.; Garnavich, Peter; Gawiser, Eric; Geary, John;
   Gee, Perry; Gibson, Robert R.; Gilmore, Kirk; Grace, Emily A.; Green,
   Richard F.; Gressler, William J.; Grillmair, Carl J.; Habib, Salman;
   Haggerty, J. S.; Hamuy, Mario; Harris, Alan W.; Hawley, Suzanne L.;
   Heavens, Alan F.; Hebb, Leslie; Henry, Todd J.; Hileman, Edward;
   Hilton, Eric J.; Hoadley, Keri; Holberg, J. B.; Holman, Matt J.;
   Howell, Steve B.; Infante, Leopoldo; Ivezic, Zeljko; Jacoby, Suzanne
   H.; Jain, Bhuvnesh; R; Jedicke; Jee, M. James; Garrett Jernigan,
   J.; Jha, Saurabh W.; Johnston, Kathryn V.; Jones, R. Lynne; Juric,
   Mario; Kaasalainen, Mikko; Styliani; Kafka; Kahn, Steven M.; Kaib,
   Nathan A.; Kalirai, Jason; Kantor, Jeff; Kasliwal, Mansi M.; Keeton,
   Charles R.; Kessler, Richard; Knezevic, Zoran; Kowalski, Adam;
   Krabbendam, Victor L.; Krughoff, K. Simon; Kulkarni, Shrinivas;
   Kuhlman, Stephen; Lacy, Mark; Lepine, Sebastien; Liang, Ming;
   Lien, Amy; Lira, Paulina; Long, Knox S.; Lorenz, Suzanne; Lotz,
   Jennifer M.; Lupton, R. H.; Lutz, Julie; Macri, Lucas M.; Mahabal,
   Ashish A.; Mandelbaum, Rachel; Marshall, Phil; May, Morgan; McGehee,
   Peregrine M.; Meadows, Brian T.; Meert, Alan; Milani, Andrea; Miller,
   Christopher J.; Miller, Michelle; Mills, David; Minniti, Dante; Monet,
   David; Mukadam, Anjum S.; Nakar, Ehud; Neill, Douglas R.; Newman,
   Jeffrey A.; Nikolaev, Sergei; Nordby, Martin; O'Connor, Paul; Oguri,
   Masamune; Oliver, John; Olivier, Scot S.; Olsen, Julia K.; Olsen,
   Knut; Olszewski, Edward W.; Oluseyi, Hakeem; Padilla, Nelson D.;
   Parker, Alex; Pepper, Joshua; Peterson, John R.; Petry, Catherine;
   Pinto, Philip A.; Pizagno, James L.; Popescu, Bogdan; Prsa, Andrej;
   Radcka, Veljko; Raddick, M. Jordan; Rasmussen, Andrew; Rau, Arne; Rho,
   Jeonghee; Rhoads, James E.; Richards, Gordon T.; Ridgway, Stephen
   T.; Robertson, Brant E.; Roskar, Rok; Saha, Abhijit; Sarajedini,
   Ata; Scannapieco, Evan; Schalk, Terry; Schindler, Rafe; Schmidt,
   Samuel; Schmidt, Sarah; Schneider, Donald P.; Schumacher, German;
   Scranton, Ryan; Sebag, Jacques; Seppala, Lynn G.; Shemmer, Ohad;
   Simon, Joshua D.; Sivertz, M.; Smith, Howard A.; Allyn Smith, J.;
   Smith, Nathan; Spitz, Anna H.; Stanford, Adam; Stassun, Keivan G.;
   Strader, Jay; Strauss, Michael A.; Stubbs, Christopher W.; Sweeney,
   Donald W.; Szalay, Alex; Szkody, Paula; Takada, Masahiro; Thorman,
   Paul; Trilling, David E.; Trimble, Virginia; Tyson, Anthony; Van
   Berg, Richard; Vanden Berk, Daniel; VanderPlas, Jake; Verde, Licia;
   Vrsnak, Bojan; Walkowicz, Lucianne M.; Wandelt, Benjamin D.; Wang,
   Sheng; Wang, Yun; Warner, Michael; Wechsler, Risa H.; West, Andrew
   A.; Wiecha, Oliver; Williams, Benjamin F.; Willman, Beth; Wittman,
   David; Wolff, Sidney C.; Wood-Vasey, W. Michael; Wozniak, Przemek;
   Young, Patrick; Zentner, Andrew; Zhan, Hu
2009arXiv0912.0201L    Altcode:
  A survey that can cover the sky in optical bands over wide fields to
  faint magnitudes with a fast cadence will enable many of the exciting
  science opportunities of the next decade. The Large Synoptic Survey
  Telescope (LSST) will have an effective aperture of 6.7 meters and an
  imaging camera with field of view of 9.6 deg^2, and will be devoted
  to a ten-year imaging survey over 20,000 deg^2 south of +15 deg. Each
  pointing will be imaged 2000 times with fifteen second exposures in six
  broad bands from 0.35 to 1.1 microns, to a total point-source depth
  of r~27.5. The LSST Science Book describes the basic parameters of
  the LSST hardware, software, and observing plans. The book discusses
  educational and outreach opportunities, then goes on to describe
  a broad range of science that LSST will revolutionize: mapping the
  inner and outer Solar System, stellar populations in the Milky Way and
  nearby galaxies, the structure of the Milky Way disk and halo and other
  objects in the Local Volume, transient and variable objects both at low
  and high redshift, and the properties of normal and active galaxies at
  low and high redshift. It then turns to far-field cosmological topics,
  exploring properties of supernovae to z~1, strong and weak lensing,
  the large-scale distribution of galaxies and baryon oscillations, and
  how these different probes may be combined to constrain cosmological
  models and the physics of dark energy.

---------------------------------------------------------
Title: Relative Kinematics of the Leading Edge and the Prominence
    in Coronal Mass Ejections
Authors: Maričić, Darije; Vršnak, Bojan; Roša, Dragan
2009SoPh..260..177M    Altcode:
  We present a statistical analysis of the relationship between the
  kinematics of the leading edge and the eruptive prominence in coronal
  mass ejections (CMEs). We study the acceleration phase of 18 CMEs in
  which kinematics was measured from the pre-eruption stage up to the
  post-acceleration phase. In all CMEs, the three part structure (the
  leading edge, the cavity, and the prominence) was clearly recognizable
  from early stages of the eruption. The data show a distinct correlation
  between the duration of the leading edge (LE) acceleration and eruptive
  prominence (EP) acceleration. In the majority of events (78%) the
  acceleration phase onset of the LE is very closely synchronized (within
  ± 20 min) with the acceleration of EP. However, in two events the LE
  acceleration started significantly earlier than the EP acceleration
  (&gt; 50 min), and in two events the EP acceleration started earlier
  than the LE acceleration (&gt; 40 min). The average peak acceleration of
  LEs (281 m s<SUP>−2</SUP>) is about two times larger than the average
  peak acceleration of EPs (136 m s<SUP>−2</SUP>). For the first time,
  our results quantitatively demonstrate the level of synchronization of
  the acceleration phase of LE and EP in a rather large sample of events,
  i.e., we quantify how often the eruption develops in a "self-similar"
  manner.

---------------------------------------------------------
Title: Analytic Modeling of the Moreton Wave Kinematics
Authors: Temmer, M.; Vršnak, B.; Žic, T.; Veronig, A. M.
2009ApJ...702.1343T    Altcode: 2009arXiv0908.3746T
  The issue whether Moreton waves are flare-ignited or coronal mass
  ejection (CME)-driven, or a combination of both, is still a matter of
  debate. We develop an analytical model describing the evolution of a
  large-amplitude coronal wave emitted by the expansion of a circular
  source surface in order to mimic the evolution of a Moreton wave. The
  model results are confronted with observations of a strong Moreton
  wave observed in association with the X3.8/3B flare/CME event from
  2005 January 17. Using different input parameters for the expansion
  of the source region, either derived from the real CME observations
  (assuming that the upward moving CME drives the wave), or synthetically
  generated scenarios (expanding flare region, lateral expansion of the
  CME flanks), we calculate the kinematics of the associated Moreton
  wave signature. Those model input parameters are determined which
  fit the observed Moreton wave kinematics best. Using the measured
  kinematics of the upward moving CME as the model input, we are not able
  to reproduce the observed Moreton wave kinematics. The observations
  of the Moreton wave can be reproduced only by applying a strong and
  impulsive acceleration for the source region expansion acting in a
  piston mechanism scenario. Based on these results we propose that the
  expansion of the flaring region or the lateral expansion of the CME
  flanks is more likely the driver of the Moreton wave than the upward
  moving CME front.

---------------------------------------------------------
Title: Type II bursts in Meter and Decameter - Hectometer Wavelength
    Ranges and Their Relation to Flares and CMEs
Authors: Prakash, O.; Umapathy, S.; Shanmugaraju, A.; Vršnak, Bojan
2009SoPh..258..105P    Altcode:
  Statistical analysis of the relationship between type II radio
  bursts appearing in the metric (m) and decameter-to-hectometer
  (DH) wavelength ranges is presented. The associated X-ray flares
  and coronal mass ejections (CMEs) are also reported. The sample is
  divided into two classes using the frequency-drift plots: Class I,
  representing those events where DH-type-II bursts are not continuation
  of m-type-II bursts and Class II, where the DH-type-II bursts are
  extensions of m-type-II bursts. Our study consists of three steps:
  i) comparison of characteristics of the Class I and II events; ii)
  correlation of m-type-II and DH-type-II burst characteristics with
  X-ray flare properties and iii) correlation of m-type-II and DH-type-II
  burst characteristics with CME properties. We have found no clear
  correlation between properties of m-type-II bursts and DH-type-II
  bursts. For example, there is no correlation between drift rates
  of m-type-II bursts and DH-type-II bursts. Similarly there is no
  correlation between their starting frequencies. In Class I events we
  found correlations between X-ray flare characteristics and properties of
  m-type-II bursts and there is no correlation between flare parameters
  and DH-type-II bursts. On the other hand, the correlation between CME
  parameters and m-type-II bursts is very weak, but it is good for CME
  parameters and DH-type-II bursts. These results indicate that Class
  I m-type-II bursts are related to the energy releases in flares,
  whereas DH-type-II bursts tend to be related to CMEs. On the contrary,
  for Class II events in the case of m-type-II and DH-type-II bursts we
  have found no clear correlation between both flare and CMEs.

---------------------------------------------------------
Title: Radial Evolution of Well-Observed Slow CMEs in the Distance
    Range 2 - 30 R <SUB>⊙</SUB>
Authors: Shanmugaraju, A.; Moon, Y. -J.; Vrsnak, Bojan; Vrbanec, Dijana
2009SoPh..257..351S    Altcode:
  We performed a detailed analysis of 27 slow coronal mass ejections
  (CMEs) whose heights were measured in at least 30 coronagraphic images
  and were characterized by a high quality index (≥4). Our primary aim
  was to study the radial evolution of these CMEs and their properties
  in the range 2 - 30 solar radii. The instantaneous speeds of CMEs
  were calculated by using successive height - time data pairs. The
  obtained speed - distance profiles [v(R)] are fitted by a power law v
  = a(R−b)<SUP>c</SUP>. The power-law indices are found to be in the
  ranges a=30 - 386, b=1.95 - 3.92, and c=0.03 - 0.79. The power-law
  exponent c is found to be larger for slower and narrower CMEs. With
  the exception of two events that had approximately constant velocity,
  all events were accelerating. The majority of accelerating events
  shows a v(R) profile very similar to the solar-wind profile deduced
  by Sheeley et al. (Astrophys. J.484, 472, 1997). This indicates that
  the dynamics of most slow CMEs are dominated by the solar wind drag.

---------------------------------------------------------
Title: Analyses of magnetic field structures for active region 10720
    using a data-driven 3D MHD model
Authors: Wu, S. T.; Wang, A. H.; Gary, G. Allen; Kucera, Ales; Rybak,
   Jan; Liu, Yang; Vrśnak, Bojan; Yurchyshyn, Vasyl
2009AdSpR..44...46W    Altcode:
  In order to understand solar eruptive events (flares and CMEs) we
  need to investigate the changes at the solar surface. Thus, we use
  a data-driven, three-dimensional magnetohydrodynamic (MHD) model to
  analyze a flare and coronal mass ejection productive active region,
  AR 10720 on January 15, 2005. The measured magnetic field from Big
  Bear Solar Observatory (BBSO) digital vector magnetograph (DGVM) was
  used to model the non-potential coronal magnetic field changes and the
  evolution of electric current before and after the event occurred. The
  numerical results include the change of magnetic flux ( Φ), the net
  electric current ( I<SUB>N</SUB>), the length of magnetic shear of the
  main neutral line ( L<SUB>ss</SUB>), the flux normalized measure of
  the field twist (α={μI<SUB>N</SUB>}/{Φ}) with μ being the magnetic
  permeability. The current helicity ( H<SUB>c</SUB>) injected into the
  corona and the photospheric surface velocity are also computed. The
  characteristic parameters of the buildup process before the event and
  the decay process after the event are investigated and the amount of
  magnetic energy converted to drive the event is estimated.

---------------------------------------------------------
Title: Morphology and density structure of post-CME current sheets
Authors: Vršnak, B.; Poletto, G.; Vujić, E.; Vourlidas, A.; Ko,
   Y. -K.; Raymond, J. C.; Ciaravella, A.; Žic, T.; Webb, D. F.;
   Bemporad, A.; Landini, F.; Schettino, G.; Jacobs, C.; Suess, S. T.
2009A&A...499..905V    Altcode: 2009arXiv0902.3705V
  Context: Eruption of a coronal mass ejection (CME) drags and “opens”
  the coronal magnetic field, presumably leading to the formation
  of a large-scale current sheet and field relaxation by magnetic
  reconnection. <BR />Aims: We analyze the physical characteristics
  of ray-like coronal features formed in the aftermath of CMEs, to
  confirm whether interpreting this phenomenon in terms of a reconnecting
  current sheet is consistent with observations. <BR />Methods: The study
  focuses on measurements of the ray width, density excess, and coronal
  velocity field as a function of the radial distance. <BR />Results: The
  morphology of the rays implies that they are produced by Petschek-like
  reconnection in the large-scale current sheet formed in the wake of
  CME. The hypothesis is supported by the flow pattern, often showing
  outflows along the ray, and sometimes also inflows into the ray. The
  inferred inflow velocities range from 3 to 30 km s<SUP>-1</SUP>, and
  are consistent with the narrow opening-angle of rays, which add up to a
  few degrees. The density of rays is an order of magnitude higher than
  in the ambient corona. The density-excess measurements are compared
  with the results of the analytical model in which the Petschek-like
  reconnection geometry is applied to the vertical current sheet, taking
  into account the decrease in the external coronal density and magnetic
  field with height. <BR />Conclusions: The model results are consistent
  with the observations, revealing that the main cause of the density
  excess in rays is a transport of the dense plasma from lower to higher
  heights by the reconnection outflow.

---------------------------------------------------------
Title: Temporal comparison of nonthermal flare emission and
    magnetic-flux change rates
Authors: Miklenic, C. H.; Veronig, A. M.; Vršnak, B.
2009A&A...499..893M    Altcode: 2009arXiv0910.1701M
  Context: To understand the mechanisms that trigger solar flares,
  we require models describing and quantifying observable responses
  to the original energy release process, since the coronal energy
  release site itself cannot be resolved with current technical
  equipment. Testing the usefulness of a particular model requires the
  comparison of its predictions with flare observations. <BR />Aims:
  To test the standard flare model (CSHKP-model), we measured the
  magnetic-flux change rate in five flare events of different GOES
  classes using chromospheric/photospheric observations and compared
  its progression with observed nonthermal flare emission. We calculated
  the cumulated positive and negative magnetic flux participating in the
  reconnection process, as well as the total reconnection flux. Finally,
  we investigated the relations between the total reconnection flux,
  the GOES class of the events, and the linear velocity of the
  flare-associated CMEs. <BR />Methods: Using high-cadence Hα and
  TRACE 1600 Å image time-series data and MDI/SOHO magnetograms, we
  measured the required observables (newly brightened flare area and
  magnetic-field strength inside this area). RHESSI and INTEGRAL hard
  X-ray time profiles in nonthermal energy bands were used as observable
  proxies for the flare-energy release rate. <BR />Results: We detected
  strong temporal correlations between the derived magnetic-flux change
  rate and the observed nonthermal emission of all events. The cumulated
  positive and negative fluxes, with flux ratios of between 0.64 and 1.35,
  were almost equivalent to each other. Total reconnection fluxes ranged
  between 1.8×10<SUP>21</SUP> Mx for the weakest event (GOES class B9.5)
  and 15.5×10<SUP>21</SUP> Mx for the most energetic one (GOES class
  X17.2). The amount of magnetic flux participating in the reconnection
  process was higher in more energetic events than in weaker ones. Flares
  with more reconnection flux were associated with faster CMEs.

---------------------------------------------------------
Title: The role of aerodynamic drag in dynamics of coronal mass
    ejections
Authors: Vršnak, Bojan; Vrbanec, Dijana; Čalogović, Jaša; Žic,
   Tomislav
2009IAUS..257..271V    Altcode:
  Dynamics of coronal mass ejections (CMEs) is strongly affected by the
  interaction of the erupting structure with the ambient magnetoplasma:
  eruptions that are faster than solar wind transfer the momentum and
  energy to the wind and generally decelerate, whereas slower ones
  gain the momentum and accelerate. Such a behavior can be expressed in
  terms of “aerodynamic” drag. We employ a large sample of CMEs to
  analyze the relationship between kinematics of CMEs and drag-related
  parameters, such as ambient solar wind speed and the CME mass. Employing
  coronagraphic observations it is demonstrated that massive CMEs are
  less affected by the aerodynamic drag than light ones. On the other
  hand, in situ measurements are used to inspect the role of the solar
  wind speed and it is shown that the Sun-Earth transit time is more
  closely related to the wind speed than to take-off speed of CMEs. These
  findings are interpreted by analyzing solutions of a simple equation
  of motion based on the standard form for the drag acceleration. The
  results show that most of the acceleration/deceleration of CMEs on
  their way through the interplanetary space takes place close to the
  Sun, where the ambient plasma density is still high. Implications for
  the space weather forecasting of CME arrival-times are discussed.

---------------------------------------------------------
Title: Cosmic ray modulation by corotating interaction regions
Authors: Čalogović, Jaša; Vršnak, Bojan; Temmer, Manuela; Veronig,
   Astrid M.
2009IAUS..257..425C    Altcode:
  We analyzed the relationship between the ground-based modulation of
  cosmic rays (CR) and corotating interaction regions (CIRs). Daily
  averaged data from 8 different neutron monitor (NM) stations were
  used, covering rigidities from R<SUB>c</SUB> = 0 - 12.91 GeV. The in
  situ solar wind data were taken from the Advanced Composition Explorer
  (ACE) database, whereas the coronal hole (CH) areas were derived from
  the Solar X-Ray Imager onboard GOES-12. For the analysis we have
  chosen a period in the declining phase of solar cycle 23, covering
  the period 25 January-5 May 2005. During the CIR periods CR decreased
  typically from 0.5% to 2%. A cross-correlation analysis showed a
  distinct anti-correlation between the magnetic field and CR, with the
  correlation coefficient (r) ranging from -0.31 to -0.38 (mean: -0.36)
  and with the CR time delay of 2 to 3 days. Similar anti-correlations
  were found for the solar wind density and velocity characterized by
  the CR time lag of 4 and 1 day, respectively. The relationship was also
  established between the CR modulation and the area of the CIR-related CH
  with the CR time lag of 5 days after the central-meridian passage of CH.

---------------------------------------------------------
Title: Type II Radio Bursts with High and Low Starting Frequencies
Authors: Shanmugaraju, Annamalai; Moon, Y. -J.; Vrsnak, Bojan
2009SoPh..254..297S    Altcode:
  We report on the detailed analysis of i) differences between the
  properties of type IIs with various starting frequencies (high: ≥100
  MHz; low: ≤50 MHz; mid: 50 MHz ≤f≤ 100 MHz) and ii) the properties
  of CMEs and flares associated with them. For this study, we considered
  a sample of type II radio bursts observed by Culgoora radio spectrograph
  from January 1998 to December 2000. The X-ray flares and CMEs associated
  with these events are identified using GOES and SOHO/LASCO data. The
  secondary aim is to study the frequency dependence on other properties
  of type IIs, flares, and CMEs. We found that the type IIs with high
  starting frequencies have larger drift rate, relative drift rate,
  and shock speed than the type IIs with low starting frequencies. The
  flares associated with high frequency type IIs are of impulsive in
  nature with shorter rise time, duration and delay between the flare
  start and type II start times than the low frequency type IIs. There
  is a distinct power - law relationship between the flare parameters
  and the starting frequencies of type II bursts, whereas the trend in
  the CME parameters shows low correlation. While the mean speed of CMEs
  is larger for the mid-frequency group, it is nearly the same for the
  high and low frequency groups. On the other hand, the percentage of
  CME association (90%) is larger for low frequency type IIs than for
  the high frequency type IIs (75%).

---------------------------------------------------------
Title: Magnetic Flux Change Rates and Nonthermal Flare Emission
Authors: Miklenic, C.; Veronig, A.; Vršnak, B.
2009CEAB...33..197M    Altcode:
  We tested the standard flare model by measuring the magnetic flux
  change rate in five flares of different GOES classes and compared it
  to the observed nonthermal flare hard X-ray emission. In addition we
  calculated the cumulated positive and negative magnetic reconnection
  flux, as well as the total reconnection flux. We also investigated the
  relations between the total reconnection flux, the GOES importance of
  the events, and the linear velocity of the flare-associated CMEs. The
  required observables (newly brightened flare area and magnetic field
  strength inside this area) were measured using high-cadence Hα and
  TRACE 1600 Å image time series along with MDI/SOHO magnetograms. RHESSI
  and INTEGRAL hard X-ray time profiles in nonthermal energy bands served
  as observable proxies for the flare energy release rate. We found
  good temporal correlations between the derived magnetic flux change
  rate and the observed nonthermal emission in all events. Cumulated
  positive and negative fluxes were roughly balanced. The amount of
  magnetic reconnection flux was larger in more energetic events than in
  weaker ones. Flares with more reconnection flux were associated with
  faster CMEs. The findings indicate that the standard flare model is
  applicable to the analysed events.

---------------------------------------------------------
Title: Commission 10: Solar Activity
Authors: Klimchuk, James A.; van Driel-Gesztelyi, Lidia; Schrijver,
   Carolus J.; Melrose, Donald B.; Fletcher, Lyndsay; Gopalswamy,
   Natchimuthuk; Harrison, Richard A.; Mandrini, Cristina H.; Peter,
   Hardi; Tsuneta, Saku; Vršnak, Bojan; Wang, Jing-Xiu
2009IAUTA..27...79K    Altcode: 2008arXiv0809.1444K
  Commission 10 deals with solar activity in all of its forms,
  ranging from the smallest nanoflares to the largest coronal mass
  ejections. This report reviews scientific progress over the roughly
  two-year period ending in the middle of 2008. This has been an exciting
  time in solar physics, highlighted by the launches of the Hinode and
  STEREO missions late in 2006. The report is reasonably comprehensive,
  though it is far from exhaustive. Limited space prevents the inclusion
  of many significant results. The report is divided into the following
  sections: Photosphere and chromosphere; Transition region; Corona and
  coronal heating; Coronal jets; flares; Coronal mass ejection initiation;
  Global coronal waves and shocks; Coronal dimming; The link between low
  coronal CME signatures and magnetic clouds; Coronal mass ejections in
  the heliosphere; and Coronal mass ejections and space weather. Primary
  authorship is indicated at the beginning of each section.

---------------------------------------------------------
Title: Cylindrical and Spherical Pistons as Drivers of MHD Shocks
Authors: Žic, Tomislav; Vršnak, Bojan; Temmer, Manuela; Jacobs, Carla
2008SoPh..253..237Z    Altcode: 2008SoPh..tmp..153Z
  We consider an expanding three-dimensional (3-D) piston as a driver
  of an MHD shock wave. It is assumed that the source-region surface
  accelerates over a certain time interval to achieve a particular maximum
  velocity. Such an expansion creates a large-amplitude wave in the
  ambient plasma. Owing to the nonlinear evolution of the wavefront, its
  profile steepens and after a certain time and distance a discontinuity
  forms, marking the onset of the shock formation. We investigate
  how the formation time and distance depend on the acceleration phase
  duration, the maximum expansion velocity (defining also acceleration),
  the Alfvén velocity (defining also Mach number), and the initial size
  of the piston. The model differs from the 1-D case, since in the 3-D
  evolution, a decrease of the wave amplitude with distance must be taken
  into account. We present basic results, focusing on the timing of the
  shock formation in the low- and high-plasma-beta environment. We find
  that the shock-formation time and the shock-formation distance are
  (1) approximately proportional to the acceleration phase duration;
  (2) shorter for a higher expansion velocity; (3) larger in a higher
  Alfvén speed environment; (4) only weakly dependent on the initial
  source size; (5) shorter for a stronger acceleration; and (6) shorter
  for a larger Alfvén Mach number of the source surface expansion. To
  create a shock causing a high-frequency type II burst and the Moreton
  wave, the source region expansion should, according to our results,
  achieve a velocity on the order of 1000 km s<SUP>−1</SUP> within a
  few minutes, in a low Alfvén velocity environment.

---------------------------------------------------------
Title: A Flare-Generated Shock during a Coronal Mass Ejection on 24
    December 1996
Authors: Magdalenić, J.; Vršnak, B.; Pohjolainen, S.; Temmer, M.;
   Aurass, H.; Lehtinen, N. J.
2008SoPh..253..305M    Altcode: 2008SoPh..tmp..120M
  We present a multiwavelength study of the large-scale coronal
  disturbances associated with the CME - flare event recorded on 24
  December 1996. The kinematics of the shock wave signature, the type
  II radio burst, is analyzed and compared with the flare evolution
  and the CME kinematics. We employ radio dynamic spectra, position
  of the Nançay Radioheliograph sources, and LASCO-C1 observations,
  providing detailed study of this limb event. The obtained velocity of
  the shock wave is significantly higher than the contemporaneous CME
  velocity (1000 and 235 km s<SUP>−1</SUP>, respectively). Moreover,
  since the main acceleration phase of the CME took place 10 - 20 min
  after the shock wave was launched, we conclude that the shock wave
  on 24 December 1996 was probably not driven by the CME. However,
  the shock wave was closely associated with the flare impulsive phase,
  indicating that it was ignited by the energy release in the flare.

---------------------------------------------------------
Title: Investigation of geomagnetic and solar activity over time
    span 1960-2001
Authors: Verbanac, G.; Vrsnak, B.; Korte, M.; Mandea, M.; Temmer, M.
2008AGUFMSH13A1502V    Altcode:
  The solar-terrestrial relationship has been widely studied by means
  of space weather indices and various solar wind parameters. In this
  study we perform such an investigation over four decades (1960--2001)
  on the global scale, and for the first time on the regional scale as
  well. The variations regarded as the remaining external field signal
  (thereafter RES) and present in the European observatory annual means
  of the Northward, X, magnetic component is used as an indicator of
  the regional geomagnetic activity and are investigated regarding
  different processes occurring on the Sun. In order to understand how
  various geomagnetic activity indices respond to the interplanetary
  disturbances during different periods of the solar cycle, the annual
  means of the solar activity index, F10.7, and geomagnetic Ap and Dst
  indices, are studied. The indices are inherently complex since they
  include contributions from different solar phenomena. By studying
  the cross-correlations we aim to distinguish between different
  generation mechanisms. The relationships between the solar parameter
  F10.7 and RES, Dst, Ap, characterized by high cross-correlation
  coefficients, suggest the possibility to evaluate the behaviour of
  these geomagnetic parameters on short timescale. We found finite
  time lags among the investigated parameters. Our study suggests a
  one year delay of both RES and Dst after F10.7. The Ap is clearly
  delayed for about two years with respect to F10.7 and about one year
  with respect to Dst and RES. This indicate that the Ap responds to
  the solar activity in a different manner than Dst and RES, which are
  dominated by the coronal mass ejections activity. On the other hand,
  it seems that Ap is more sensitive to the high--speed streams (HSS)
  and Alfvenic waves present in HSS. The existence of time lags gives
  us the possibility to forecast different parameters. Importantly, the
  proposed forecasting procedure offers the possibility to reconstruct
  the F10.7 from the inferred geomagnetic activity for the epochs prior
  to solar activity monitoring. This study contributes to understanding
  some physical processes on the Sun that cause the perturbations in the
  near-Earth interplanetary space and consequently in the Earth's magnetic
  field. Moreover such investigations may provide a better insight into
  the time evolution of the open and closed solar magnetic field, and into
  long term changes in the solar activity with related physical processes.

---------------------------------------------------------
Title: Origin of Coronal Shock Waves. Invited Review
Authors: Vršnak, Bojan; Cliver, Edward W.
2008SoPh..253..215V    Altcode: 2008SoPh..tmp..142V
  The basic idea of the paper is to present transparently and confront
  two different views on the origin of large-scale coronal shock waves,
  one favoring coronal mass ejections (CMEs), and the other one preferring
  flares. For this purpose, we first review the empirical aspects of the
  relationship between CMEs, flares, and shocks (as manifested by radio
  type II bursts and Moreton waves). Then, various physical mechanisms
  capable of launching MHD shocks are presented. In particular, we
  describe the shock wave formation caused by a three-dimensional piston,
  driven either by the CME expansion or by a flare-associated pressure
  pulse. Bearing in mind this theoretical framework, the observational
  characteristics of CMEs and flares are revisited to specify advantages
  and drawbacks of the two shock formation scenarios. Finally,
  we emphasize the need to document clear examples of flare-ignited
  large-scale waves to give insight on the relative importance of flare
  and CME generation mechanisms for type II bursts/Moreton waves.

---------------------------------------------------------
Title: Dynamics of coronal mass ejections. The mass-scaling of the
    aerodynamic drag
Authors: Vršnak, B.; Vrbanec, D.; Čalogović, J.
2008A&A...490..811V    Altcode:
  Context: Coronal and interplanetary propagation of coronal mass
  ejections (CMEs) is strongly affected by aerodynamic drag. <BR />Aims:
  The dependence of the drag acceleration on the mass of the CMEs is
  investigated to establish a quantitative empirical relationship, which
  might be important in semi-empirical space-weather forecasting. <BR
  />Methods: We employ a large sample of CMEs observed in the radial
  distance range of 2-30 solar radii by the Large Angle and Spectrometric
  Coronagraph on board the SoHO mission to statistically analyze the
  acceleration-velocity relationship in subsamples of various classes of
  CME masses. <BR />Results: It is demonstrated that the slope and the
  v-axis intercept of the anti-correlation of the CME acceleration a and
  velocity v depend on the mean mass of CMEs included in the sample. The
  slope k of the correlation is less steep for subsamples of higher
  masses, revealing that massive CMEs are less affected by the aerodynamic
  drag. Furthermore, it is found that the v-axis intercept is shifted
  to higher velocities for subsamples of higher masses. This indicates
  that, on average, the driving force is greater in more massive CMEs. <BR
  />Conclusions: The empirically established dependence of the a(v) slope
  on the CME mass is very close to the dependence kpropto m<SUP>-1/3</SUP>
  which follows from the physical characteristics of the aerodynamic drag.

---------------------------------------------------------
Title: Processes and mechanisms governing the initiation and
    propagation of CMEs
Authors: Vršnak, B.
2008AnGeo..26.3089V    Altcode:
  The most important observational characteristics of coronal mass
  ejections (CMEs) are summarized, emphasizing those aspects which are
  relevant for testing physical concepts employed to explain the CME
  take-off and propagation. In particular, the kinematics, scalings,
  and the CME-flare relationship are stressed. Special attention is paid
  to 3-dimensional (3-D) topology of the magnetic field structures,
  particularly to aspects related to the concept of semi-toroidal
  flux-rope anchored at both ends in the dense photosphere and embedded
  in the coronal magnetic arcade. Observations are compared with physical
  principles and concepts employed in explaining the CME phenomenon, and
  implications are discussed. A simple flux-rope model is used to explain
  various stages of the eruption. The model is able to reproduce all basic
  observational requirements: stable equilibrium and possible oscillations
  around equilibrium, metastable state and possible destabilization
  by an external disturbance, pre-eruptive gradual-rise until loss of
  equilibrium, possibility of fallback events and failed eruptions,
  relationship between impulsiveness of the CME acceleration and the
  source-region size, etc. However, it is shown that the purely ideal
  MHD process cannot account for highest observed accelerations which
  can attain values up to 10 km s<SUP>-2</SUP>. Such accelerations can be
  achieved if the process of reconnection beneath the erupting flux-rope
  is included into the model. Essentially, the role of reconnection is in
  changing the magnetic flux associated with the flux-rope current and
  supplying "fresh" poloidal magnetic flux to the rope. These effects
  help sustain the electric current flowing along the flux-rope, and
  consequently, reinforce and prolong the CME acceleration. The model
  straightforwardly explains the observed synchronization of the flare
  impulsive phase and the CME main-acceleration stage, as well as the
  correlations between various CME and flare parameters.

---------------------------------------------------------
Title: Two-spacecraft reconstruction of a magnetic cloud and
    comparison to its solar source
Authors: Möstl, C.; Miklenic, C.; Farrugia, C. J.; Temmer, M.;
   Veronig, A.; Galvin, A. B.; Vršnak, B.; Biernat, H. K.
2008AnGeo..26.3139M    Altcode:
  This paper compares properties of the source region with those inferred
  from satellite observations near Earth of the magnetic cloud which
  reached 1 AU on 20 November 2003. We use observations from space
  missions SOHO and TRACE together with ground-based data to study
  the magnetic structure of the active region NOAA 10501 containing
  a highly curved filament, and determine the reconnection rates and
  fluxes in an M4 flare on 18 November 2003 which is associated with
  a fast halo CME. This event has been linked before to the magnetic
  cloud on 20 November 2003. We model the near-Earth observations with
  the Grad-Shafranov reconstruction technique using a novel approach in
  which we optimize the results with two-spacecraft measurements of the
  solar wind plasma and magnetic field made by ACE and WIND. The two
  probes were separated by hundreds of Earth radii. They pass through
  the axis of the cloud which is inclined -50 degree to the ecliptic. The
  magnetic cloud orientation at 1 AU is consistent with an encounter with
  the heliospheric current sheet. We estimate that 50% of its poloidal
  flux has been lost through reconnection in interplanetary space. By
  comparing the flare ribbon flux with the original cloud fluxes we infer
  a flux rope formation during the eruption, though uncertainties are
  still significant. The multi-spacecraft Grad-Shafranov method opens
  new vistas in probing of the spatial structure of magnetic clouds in
  STEREO-WIND/ACE coordinated studies.

---------------------------------------------------------
Title: Large-scale Coronal Waves Observed with EUVI/STEREO
Authors: Veronig, A.; Temmer, M.; Vrsnak, B.
2008ESPM...12.2.97V    Altcode:
  We report first observations and analysis of flare/CME associated
  large-scale coronal waves (so-called "EIT waves") observed with
  high time cadence by the EUVI instruments onboard the recent STEREO
  mission. The EIT instrument onboard SOHO for the first time directly
  imaged global disturbances in the solar corona, but the observations
  are severely hampered by the low cadence of EIT (12-15 min). Thus,
  the nature and origin of these large-scale disturbances are still
  not sufficiently constraint by observations, and it is an intense
  matter of debate whether EIT waves: a) are the coronal counterparts of
  Moreton waves observed in the chromosphere; b) are caused by the flare
  explosive energy release or by the erupting CME; c) are waves at all or
  rather propagating disturbances related to magnetic field line opening
  and restructuring associated with the CME lift-off. The high cadence
  full-disk coronal imaging by the EUVI instruments on the twin STEREO
  spacecraft provide us with the unprecedented opportunity to study the
  dynamics and origin of flare/CME associated coronal waves. We present
  first studies of global coronal waves observed with EUVI finding wave
  deceleration, indicative of an MHD blast wave (Veronig et al. 2008,
  ApJ Lett., in press).

---------------------------------------------------------
Title: Relation between CME SchmiederAcceleration Profile and Flare
    Energy Release derived from Combined STEREO and RHESSI Observations
Authors: Temmer, M.; Veronig, A. M.; Vrsnak, B.
2008ESPM...12.2.96T    Altcode:
  In the standard flare/CME picture magnetic reconnection occurs in
  a current sheet formed behind the CME, which may provide a feedback
  relationship between both phenomena. To study the relationship of the
  large-scale CME acceleration and the energy release in the associated
  flare we analyze three well observed events. The observations cover
  the early (low corona) evolution of the CMEs with the EUVI instruments
  aboard the twin STEREO spacecraft and the RHESSI hard X-ray emission
  of the associated flare. Since the flare hard X-rays are due to fast
  electrons, they provide the most direct indicator of the evolution of
  the flare energy release in the flare. The results are compared to case
  studies for halo-CMEs where a close synchronization between the CME
  acceleration and the flare energy release was found (Temmer et al.,
  ApJ, 2008, 673, L95).

---------------------------------------------------------
Title: High-Cadence Observations of a Global Coronal Wave by
    STEREO EUVI
Authors: Veronig, Astrid M.; Temmer, Manuela; Vršnak, Bojan
2008ApJ...681L.113V    Altcode: 2008arXiv0806.0710V
  We report a large-scale coronal wave (so-called EIT wave) observed
  with high cadence by EUVI on board STEREO in association with the GOES
  B9.5 flare and double CME event on 2007 May 19. The EUVI instruments
  provide us with the unprecedented opportunity to study the dynamics of
  flare/CME associated coronal waves. The coronal wave under study reveals
  deceleration, indicative of a freely propagating MHD wave. Complementary
  analysis of the associated flare and erupting filament/CME hint at wave
  initiation by the CME expanding flanks, which drive the wave only over
  a limited distance. The associated flare is very weak and occurs too
  late to account for the wave initiation.

---------------------------------------------------------
Title: Analysis of a Moreton Wave Associated with the X17.2/4B
    Flare/CME of 28-10-2003
Authors: Muhr, M.; Temmer, M.; Veronig, A.; Vršnak, B.; Hanslmeier, A.
2008CEAB...32...79M    Altcode:
  The fast Moreton wave of 28-Oct-2003 associated with the extreme X17.2
  solar flare/CME event is studied. It can be followed in four sectors,
  spanning almost over 360° on the visible solar disc. The mean wave
  velocity lies in the range of v∼900-1000 km s^{-1}. We find two
  wave ignition centres on opposite edges of the source region, which
  may indicate that the wave is driven by the CME expanding flanks.

---------------------------------------------------------
Title: Proper Motions of Coronal Bright Points
Authors: Brajša, R.; Wöhl, H.; Vršnak, B.; Ruždjak, V.; Clette,
   F.; Hochedez, J. -F.; Verbanac, G.; Skokić, I.; Hanslmeier, A.
2008CEAB...32..165B    Altcode:
  Full-field full-resolution solar images obtained by the Extreme
  Ultraviolet Imaging Telescope on board the Solar and Heliospheric
  Observatory are used to analyse proper motions, velocity distributions,
  lifetimes, and diffusion coefficient of coronal bright points. The
  results obtained by the interactive method for three tracer subtypes
  (point-like structures, small loops, and small active regions)
  of coronal bright points for the period 4 June 1998 to 22 May 1999
  are presented and compared. Distributions of meridional velocities,
  residual azimuthal velocities and velocities of proper motions are
  presented for the three tracer subtypes. Lifetimes up to 54 hours
  are found for 98% of all observed coronal bright points. Small active
  regions last on the average longer than point-like structures and small
  loops. The correlation between the absolute velocity of proper motion
  and lifetime is investigated and the mean free path (in the range from
  3000 km to 15000 km) and the diffusion coefficient (approximately 200
  km<SUP>2</SUP>/s) of coronal bright points are estimated. Finally,
  characteristics of the random walk process associated to the motions
  of coronal bright points are discussed in the Appendix.

---------------------------------------------------------
Title: Acceleration in Fast Halo CMEs and Synchronized Flare HXR
    Bursts
Authors: Temmer, M.; Veronig, A. M.; Vršnak, B.; Rybák, J.; Gömöry,
   P.; Stoiser, S.; Maričić, D.
2008ApJ...673L..95T    Altcode:
  We study two well-observed, fast halo CMEs, covering the full CME
  kinematics including the initiation and impulsive acceleration phase,
  and their associated flares. We find a close synchronization between the
  CME acceleration profile and the flare energy release as indicated by
  the RHESSI hard X-ray flux onsets, as well as peaks occur simultaneously
  within 5 minutes. These findings indicate a close physical connection
  between both phenomena and are interpreted in terms of a feedback
  relationship between the CME dynamics and the reconnection process in
  the current sheet beneath the CME.

---------------------------------------------------------
Title: Large-scale coronal waves observed with STEREO/EUVI
Authors: Veronig, Astrid; Temmer, Manuela; Vrsnak, Bojan
2008cosp...37.3328V    Altcode: 2008cosp.meet.3328V
  The EUVI instruments onboard the twin STEREO spacecraft provide
  high-cadence full-disk imaging of the solar atmosphere with four
  different filters at EUV wavelengths. These observations are highly
  suitable to study the kinematics and dynamics of flare/CME associated
  coronal waves, so-called "EIT waves". We present a detailed analysis
  of one coronal wave captured by the EUVI instruments, with particular
  emphasis on the wave dynamics and its connection to the associated
  flare (RHESSI hard X-rays) and CME (STEREO COR1) in terms of blast
  wave versus driven wave scenario.

---------------------------------------------------------
Title: Dynamics of plasmoids formed by the current sheet tearing
Authors: Bárta, M.; Vršnak, B.; Karlický, M.
2008A&A...477..649B    Altcode:
  Context: Moving blob-like features observed in the soft X-ray and
  EUV range above flare-loops are often interpreted as signatures of
  plasmoids formed by the current sheet tearing in the flare-associated
  reconnection process. <BR />Aims: We investigate the evolution of
  the flare-associated current sheet numerically in order to analyse
  the kinematics and dynamics of plasmoids. The goal is to explain the
  broad diversity of kinematical properties of the plasmoid signatures
  recorded by various observational techniques. <BR />Methods: We
  performed a 2-dimensional resistive-MHD numerical simulation of
  the reconnection starting from the Harris-type current sheet. After
  identifying the plasmoids, we followed their motion to determine basic
  kinematical parameters (velocity and acceleration), and we analysed
  the associated magnetic field topology. <BR />Results: The simulation
  reveals a broad variety of the kinematical/dynamical properties of
  plasmoids - after formation, a plasmoid can move upward, downward, or
  can even change its direction of propagation. The highest velocities,
  in the range of the ambient Alfvén speed, are found in the case of
  upward propagating plasmoids. The acceleration is determined by the
  net magnetic field tension of the reconnected field lines. Downwardly
  propagating plasmoids achieve only a fraction of the ambient Alfvén
  speed. They strongly decelerate during the coalescence with low-lying
  flare-loops, when distinct energy-release peaks occur and loop system
  oscillations are excited. <BR />Conclusions: The presented results
  explain, qualitatively and quantitatively, the broad spectrum of
  kinematical properties of various observational features attributed
  to the current-sheet plasmoids.

---------------------------------------------------------
Title: The role of reconnection in the initiation, acceleration,
    and interplanetary propagation of CMEs
Authors: Vrsnak, Bojan
2008cosp...37.3368V    Altcode: 2008cosp.meet.3368V
  The central issue of the presentation is the role of reconnection in the
  acceleration of coronal mass ejections (CMEs). Following basic physical
  concepts it is demonstrated that impulsive acceleration of fast CMEs is
  not possible without reconnection. In the absence of reconnection the
  magnetic flux associated with the erupting structure remains conserved,
  causing the inductive decay of the electric current and cessation
  of the Lorentz force. Under such circumstances, the acceleration is
  constrained to values in the order of 100 m s-2 and acts over distances
  too short to provide velocities ∼ 1000 km s-1 . However, if the
  flare-associated reconnection in the wake of the erupting flux-rope
  supplies the rope with additional poloidal flux, the Lorentz-force
  acceleration can attain values up to 10 km s-2 and prolong to large
  heights. The results of a simple analytical model of a semitoroidal
  line-tied flux-rope are confronted with observations: various aspects
  of the CME-flare relationship are addressed, particularly emphasizing
  proxy measurements of the reconnected flux. Beside this central
  topic, the role of reconnection in the evolution and destabilization
  of the pre-eruptive structure is discussed, focusing on scenarios
  that lead to loss of equilibrium. Finally, the effect of reconnection
  ahead/aside of the CME during its propagation through the upper corona
  and interplanetary space is addressed.

---------------------------------------------------------
Title: Synchronization between the CME acceleration and the energy
    release in the associated flare
Authors: Temmer, Manuela; Veronig, Astrid; Vrsnak, Bojan
2008cosp...37.3167T    Altcode: 2008cosp.meet.3167T
  In the standard flare/CME picture magnetic reconnection occurs in a
  current sheet formed behind the CME, which is indicative of a feedback
  relationship between both phenomena. We analyze two X-class flare/CME
  events which were well covered by RHESSI hard X-ray observations,
  and the early evolution of the CMEs could be observed in TRACE and
  GOES/SXI images. Since the flare hard X-rays are due to fast electrons,
  they provide the most direct indicator of the evolution of the energy
  release in the flare. This data set enables us to study in detail
  the relationship of the large-scale CME acceleration and the energy
  release in the associated flare.

---------------------------------------------------------
Title: Projection effects in coronal mass ejections studied with
    STEREO and SoHO
Authors: Temmer, Manuela; Preiss, Stefanie; Veronig, Astrid; Vrsnak,
   Bojan
2008cosp...37.3168T    Altcode: 2008cosp.meet.3168T
  The STEREO mission consists of two identical satellites, positioned
  ahead (A) and behind (B) the Earth, which observe the Sun from viewing
  angles different from that of LASCO aboard SoHO (positioned at L1). The
  kinematics (speed) and width of a coronal mass ejection (CME) is derived
  by measuring distinct CME features observed in projection against the
  plane of sky. As STEREO-A, STEREO-B, and LASCO/SoHO, observe a CME
  from three different viewing angles, the resulting CME kinematics and
  widths differ. By combining the observations from the three satellites
  we study for several well observed CMEs the importance of projection
  effects for the CME kinematics and expansion.

---------------------------------------------------------
Title: On the solar rotation and activity
Authors: Brajša, R.; Wöhl, H.; Ruždjak, D.; Vršnak, B.; Verbanac,
   G.; Svalgaard, L.; Hochedez, J. -F.
2007AN....328.1013B    Altcode:
  The interaction between differential rotation and magnetic fields in
  the solar convection zone was recently modelled by Brun (2004). One
  consequence of that model is that the Maxwell stresses can oppose the
  Reynolds stresses, and thus contribute to the transport of the angular
  momentum towards the solar poles, leading to a reduced differential
  rotation. So, when magnetic fields are weaker, a more pronounced
  differential rotation can be expected, yielding a higher rotation
  velocity at low latitudes taken on the average. This hypothesis
  is consistent with the behaviour of the solar rotation during the
  Maunder minimum. In this work we search for similar signatures of
  the relationship between the solar activity and rotation determined
  tracing sunspot groups and coronal bright points. We use the extended
  Greenwich data set (1878-1981) and a series of full-disc solar images
  taken at 28.4 nm with the EIT instrument on the SOHO spacecraft
  (1998-2000). We investigate the dependence of the solar rotation on
  the solar activity (described by the relative sunspot number) and
  the interplanetary magnetic field (calculated from the interdiurnal
  variability index). Possible rotational signatures of two weak solar
  activity cycles at the beginning of the 20th century (Gleissberg
  minimum) are discussed.

---------------------------------------------------------
Title: The magnetic flux and self-inductivity of a thick toroidal
    current
Authors: Žic, Tomislav; Vršnak, Bojan; Skender, Marina
2007JPlPh..73..741Z    Altcode: 2007JPlPh..73..741A
  We investigate numerically the magnetic flux and
  self-inductivity of a toroidal current I of arbitrary aspect
  ratio (R<SUB>0</SUB>/r<SUB>0</SUB> = 1/η, where R<SUB>0</SUB>
  and r<SUB>0</SUB> are the major and the minor torus radii,
  respectively). The total flux Ψ is represented by the sum of the
  flux outside the torus envelope (Ψ<SUB>o</SUB>) and the internal
  flux within the torus body (Ψ<SUB>i</SUB>). Analogously, the total
  inductivity is expressed as L = L<SUB>o</SUB> + L<SUB>i</SUB>. The
  outside self-inductivity is determined directly from the magnetic
  flux Ψ<SUB>o</SUB>, utilizing Ψ<SUB>o</SUB> = L<SUB>o</SUB>
  I. On the other hand, the internal inductivity is evaluated as the
  magnetic energy contained in the poloidal field. The calculations are
  performed for three different radial profiles of the current density,
  j(r). <P />It is found that Ψ<SUB>o</SUB>(η) and L<SUB>o</SUB>
  (η) depend only very weakly on the form of j(r). On the other hand,
  Ψ<SUB>i</SUB> and L<SUB>i</SUB> do not depend on η, but depend on
  the form of j(r). In the range 0.02 η 0.5, the numerical values of
  L<SUB>o</SUB> can be very well fitted by the function of the form
  L<SUB>o</SUB><SUP>fit1</SUP>(η) = -A log(η) - B. Such a relation
  is analogous to that for a slender torus, although the coefficients
  are different. For η 0.01 the slender-torus approximation
  (L<SUB>o</SUB>*) matches the numerical results better than our
  function L<SUB>o</SUB><SUP>fit1</SUP>, whereas for thicker tori,
  L<SUB>o</SUB><SUP>fit1</SUP> becomes more appropriate. It is shown
  that, beyond η 0.1, the departure of the slender-torus analytical
  expression from the numerical values becomes greater than 10%, and the
  difference becomes larger than 100% at η 0.55. In the range η 0.5,
  the numerical values of L<SUB>o</SUB> can be very well expressed
  by the function L<SUB>o</SUB><SUP>fit2</SUP>(η)=c<SUB>1</SUB>
  (1 - η)<SUP>c<SUB>2</SUB></SUP>. Furthermore, since the internal
  flux and inductivity become larger than that outside the envelope,
  Ψ<SUB>i</SUB> and L<SUB>i</SUB> become larger than Ψ<SUB>o</SUB> and
  L<SUB>o</SUB>. The total inductivity L<SUB>tot</SUB><SUP>fit</SUP>
  = L<SUB>o</SUB><SUP>fit</SUP> + L<SUB>i</SUB>, calculated by
  appropriately employing our functions L<SUB>o</SUB><SUP>fit1</SUP>
  and L<SUB>o</SUB><SUP>fit2</SUP>, never deviates by more than 1%
  from the numerically determined values of L<SUB>tot</SUB>.

---------------------------------------------------------
Title: Transit times of interplanetary coronal mass ejections and
    the solar wind speed
Authors: Vršnak, B.; Žic, T.
2007A&A...472..937V    Altcode:
  Aims: The Sun-Earth transit time of interplanetary coronal
  mass ejections (ICMEs) is one of central issues of space weather
  forecasting. Our aim is to find out to what degree the ICME transit
  time depends on the solar wind speed. Methods. Two samples of coronal
  mass ejections (CMEs) and the associated ICMEs are used to analyze
  the relationship between transit times, TT, and the solar wind speed,
  w, measured at 1 AU ahead and behind the ICME. Results. We found a
  distinct correlation TT(w), clearly showing that the transit time is
  dependent not only on the ICME take-off speed v<SUB>CME</SUB>, but also
  on the solar wind speed. After dividing the samples into the solar wind
  speed bins w≤400, 400 &lt; w ≤ 500, w &gt; 500 km s^-1, we compared
  the corresponding TT(v<SUB>CME</SUB>) correlations to find that the
  transit times in the case of w ≤ 400 km s^-1 subset are longer, on
  average, for about 20-30 hours than in the case of the w &gt; 500 km
  s^1 subset. Conclusions. Since the ICME transit time is significantly
  influenced by the solar wind speed, this effect should be included in
  statistical and kinematical methods of the space weather forecast.

---------------------------------------------------------
Title: Large amplitude oscillatory motion along a solar filament
Authors: Vršnak, B.; Veronig, A. M.; Thalmann, J. K.; Žic, T.
2007A&A...471..295V    Altcode: 2007arXiv0707.1752V
  Context: Large amplitude oscillations of solar filaments is a phenomenon
  that has been known for more than half a century. Recently, a new mode
  of oscillations, characterized by periodical plasma motions along
  the filament axis, was discovered. <BR />Aims: We analyze such an
  event, recorded on 23 January 2002 in Big Bear Solar Observatory Hα
  filtergrams, to infer the triggering mechanism and the nature of the
  restoring force. <BR />Methods: Motion along the filament axis of a
  distinct buldge-like feature was traced, to quantify the kinematics of
  the oscillatory motion. The data were fitted by a damped sine function
  to estimate the basic parameters of the oscillations. To identify the
  triggering mechanism, morphological changes in the vicinity of the
  filament were analyzed. <BR />Results: The observed oscillations of the
  plasma along the filament were characterized by an initial displacement
  of 24 Mm, an initial velocity amplitude of 51 km s<SUP>-1</SUP>,
  a period of 50 min, and a damping time of 115 min. We interpret
  the trigger in terms of poloidal magnetic flux injection by magnetic
  reconnection at one of the filament legs. The restoring force is caused
  by the magnetic pressure gradient along the filament axis. The period of
  oscillations, derived from the linearized equation of motion (harmonic
  oscillator) can be expressed as P=π√{2}L/v_Aϕ≈4.4L/v_Aϕ, where
  v_Aϕ =B<SUB>ϕ0</SUB>/√μ_0ρ represents the Alfvén speed based
  on the equilibrium poloidal field B<SUB>ϕ0</SUB>. <BR />Conclusions:
  Combination of our measurements with some previous observations of
  the same kind of oscillations shows good agreement with the proposed
  interpretation. <P />Movie to Fig. 1 is only available in electronic
  form at http://www.aanda.org

---------------------------------------------------------
Title: Projection effects in coronal mass ejections
Authors: Vršnak, B.; Sudar, D.; Ruždjak, D.; Žic, T.
2007A&A...469..339V    Altcode:
  Context: Basic observational parameters of a coronal mass ejection
  (CME) are its speed and angular width. Measurements of the CME speed
  and angular width are severely influenced by projection effects. <BR
  />Aims: The goal of this paper is to investigate a statistical
  relationship between the plane-of-sky speeds of CMEs and the direction
  of their propagation, hopefully providing an estimate of the true
  speeds of CMEs. <BR />Methods: We analyze the correlation between
  the plane-of-sky velocity and the position of the CME source region,
  employing several non-halo CME samples. The samples are formed applying
  various restrictions to avoid crosstalk of relevant parameters. For
  example, we select only CMEs observed to radial distances larger than
  10 solar radii; we omit CMEs showing a considerable acceleration in the
  considered distance range and treat CMEs of different angular widths
  separately. Finally, we combine these restriction criteria, up to the
  limits beyond which the statistical significance of the results becomes
  ambiguous. <BR />Results: A distinct anti-correlation is found between
  the angular width of CMEs and their source-region position, clearly
  showing an increasing trend towards the disc center. Similarly, all of
  the considered subsamples show a correlation between the CME projected
  speed and the distance of the source region from the disc center. On
  average, velocities of non-halo limb-CMEs are 1.5-2 times higher than
  in the case of non-halo CMEs launched from regions located close to
  the disc center. <BR />Conclusions: Unfortunately, the established
  empirical relationships provide only a rough estimate of the velocity
  correction as a function of the source-region location. To a certain
  degree, the results can be explained in terms of CME cone models, but
  only after taking crosstalk of various parameters and observational
  artifacts into account.

---------------------------------------------------------
Title: Periodic Appearance of Coronal Holes and the Related Variation
    of Solar Wind Parameters
Authors: Temmer, Manuela; Vršnak, Bojan; Veronig, Astrid M.
2007SoPh..241..371T    Altcode:
  We compared the variability of coronal hole (CH) areas (determined
  from daily GOES/SXI images) with solar wind (daily ACE data) and
  geomagnetic parameters for the time span 25 January 2005 until 11
  September 2005 (late declining phase of solar cycle 23). Applying
  wavelet spectral analysis, a clear 9-day period is found in the
  CH time series. The GOES/SXI image sequence suggests that this
  periodic variation is caused by a mutual triangular distribution of
  CHs ∼120° apart in longitude. From solar wind parameters a 9-day
  periodicity was obtained as well, simultaneously with the 9-day period
  in the CH area time series. These findings provide strong evidence
  that the 9-day period in solar wind parameters, showing up as higher
  harmonic of the solar rotation frequency, is caused by the "periodic"
  longitudinal distribution of CHs on the Sun recurring for several
  solar rotations. The shape of the wavelet spectrum from the Dst index
  matches only weakly with that from the CH areas and is more similar to
  the wavelet spectrum of the solar wind magnetic field magnitude. The
  distinct 9-day period does not show up in sunspot group areas which
  gives further evidence that the solar wind modulation is strongly
  related to CH areas but not to active region complexes. The wavelet
  power spectra for the whole ACE data range (∼1998 - 2006) suggest that
  the 9-day period is not a singular phenomenon occurring only during
  a specific time range close to solar minimum but is occasionally also
  present during the maximum and decay phase of solar cycle 23. The main
  periods correspond to the solar rotation (27<SUP>d</SUP>) as well as
  to the second (13.5<SUP>d</SUP>) and third (9<SUP>d</SUP>) harmonic.

---------------------------------------------------------
Title: Acceleration Phase of Coronal Mass Ejections: I. Temporal
    and Spatial Scales
Authors: Vršnak, Bojan; Maričić, Darije; Stanger, Andrew L.;
   Veronig, Astrid M.; Temmer, Manuela; Roša, Dragan
2007SoPh..241...85V    Altcode:
  We study kinematics of 22 coronal mass ejections (CMEs) whose
  motion was traced from the gradual pre-acceleration phase up to
  the post-acceleration stage. The peak accelerations in the studied
  sample range from 40, up to 7000 m s<SUP>−2</SUP>, and are inversely
  proportional to the acceleration phase duration and the height range
  involved. Accelerations and velocities are, on average, larger in CMEs
  launched from a compact source region. The acceleration phase duration
  is proportional to the source region dimensions; i.e., compact CMEs
  are accelerated more impulsively. Such behavior is interpreted as
  a consequence of stronger Lorentz force and shorter Alfvén time
  scales involved in compact CMEs (with stronger magnetic field and
  larger Alfvén speed being involved at lower heights). CMEs with
  larger accelerations and velocities are on average wider, whereas the
  widths are not related to the source region dimensions. Such behavior is
  explained in terms of the field pile-up ahead of the erupting structure,
  which is more effective in the case of a strongly accelerated structure.

---------------------------------------------------------
Title: Acceleration Phase of Coronal Mass Ejections:
    II. Synchronization of the Energy Release in the Associated Flare
Authors: Maričić, Darije; Vršnak, Bojan; Stanger, Andrew L.;
   Veronig, Astrid M.; Temmer, Manuela; Roša, Dragan
2007SoPh..241...99M    Altcode:
  We analyze the relationship between the acceleration of coronal mass
  ejections (CMEs) and the energy release in associated flares, employing
  a sample of 22 events in which the CME kinematics were measured from
  the pre-eruption stage up to the post-acceleration phase. The data
  show a distinct correlation between the duration of the acceleration
  phase and the duration of the associated soft X-ray (SXR) burst rise,
  whereas the CME peak acceleration and velocity are related to the
  SXR peak flux. In the majority of events the acceleration started
  earlier than the SXR burst, and it is usually prolonged after the
  SXR burst maximum. In about one half of the events the acceleration
  phase is very closely synchronized with the fastest growth of the SXR
  burst. An additional one quarter of the events may be still considered
  as relatively well-synchronized, whereas in the remaining quarter of the
  events there is a considerable mismatch. The results are interpreted
  in terms of the feedback relationship between the CME dynamics and
  the reconnection process in the wake of the CME.

---------------------------------------------------------
Title: Coronal Holes and Solar Wind High-Speed Streams:
    II. Forecasting the Geomagnetic Effects
Authors: Vršnak, Bojan; Temmer, Manuela; Veronig, Astrid M.
2007SoPh..240..331V    Altcode:
  We present a simple method of forecasting the geomagnetic storms caused
  by high-speed streams (HSSs) in the solar wind. The method is based
  on the empirical correlation between the coronal hole area/position
  and the value of the Dst index, which is established in a period of
  low interplanetary coronal mass ejection (ICME) activity. On average,
  the highest geomagnetic activity, i.e., the minimum in Dst, occurs
  four days after a low-latitude coronal hole (CH) crosses the central
  meridian. The amplitude of the Dst dip is correlated with the CH area
  and depends on the magnetic polarity of the CH due to the Russell -
  McPherron effect. The Dst variation may be predicted by employing the
  expression Dst(t)=(−65±25×cos λ)[A(t<SUP>*</SUP>)]<SUP>0.5</SUP>,
  where A(t<SUP>*</SUP>) is the fractional CH area measured in the
  central-meridian slice [−10°,10°] of the solar disc, λ is the
  ecliptic longitude of the Earth, ± stands for positive/negative CH
  polarity, and t−t<SUP>*</SUP>=4 days. In periods of low ICME activity,
  the proposed expression provides forecasting of the amplitude of the
  HSS-associated Dst dip to an accuracy of ≈30%. However, the time of
  occurrence of the Dst minimum cannot be predicted to better than ±2
  days, and consequently, the overall mean relative difference between
  the observed and calculated daily values of Dst ranges around 50%.

---------------------------------------------------------
Title: Coronal Holes and Solar Wind High-Speed Streams: I. Forecasting
    the Solar Wind Parameters
Authors: Vršnak, Bojan; Temmer, Manuela; Veronig, Astrid M.
2007SoPh..240..315V    Altcode:
  We analyze the relationship between the coronal hole (CH) area/position
  and physical characteristics of the associated corotating high-speed
  stream (HSS) in the solar wind at 1 AU. For the analysis we utilize the
  data in the period DOY 25 - 125 of 2005, characterized by a very low
  coronal mass ejection (CME) activity. Distinct correlations between
  the daily averaged CH parameters and the solar wind characteristics
  are found, which allows us to forecast the solar wind velocity v,
  proton temperature T, proton density n, and magnetic field strength B,
  several days in advance in periods of low CME activity. The forecast
  is based on monitoring fractional areas A, covered by CHs in the
  meridional slices embracing the central meridian distance ranges
  [−40°,−20°], [−10°,10°], and [20°,40°]. On average, the
  peaks in the daily values of n, B, T, and v appear delayed by 1, 2,
  3, and 4 days, respectively, after the area A attains its maximum
  in the central-meridian slice. The peak values of the solar wind
  parameters are correlated to the peak values of A, which provides
  also forecasting of the peak values of n, B, T, and v. The most
  accurate prediction can be obtained for the solar wind velocity, for
  which the average relative difference between the calculated and the
  observed peak values amounts to \overline{\vertδ\vert}≈10 %. The
  forecast reliability is somewhat lower in the case of T, B, and n (
  \overline{\vertδ\vert}≈20 , 30, and 40%, respectively). The space
  weather implications are discussed, including the perspectives for
  advancing the real-time calculation of the Sun - Earth transit times
  of coronal mass ejections and interplanetary shocks, by including more
  realistic real-time estimates of the solar wind characteristics.

---------------------------------------------------------
Title: Observational Characteristics of Magnetic Reconnection in a
    Two-Ribbon Flare
Authors: Miklenic, C. H.; Veronig, A. M.; Vršnak, B.; Hanslmeier, A.
2007CEAB...31...39M    Altcode:
  A well-observed GOES M3.9 two-ribbon flare was analysed in order
  to derive the local reconnection rate (coronal electric field) and
  the global reconnection rate (magnetic flux change rate), as well
  as the energy release rate (Poynting flux) in a two-ribbon flare
  from chromospheric/photospheric observations, using TRACE 1600 Å,
  Kanzelhöhe Hα, SOHO/MDI, and RHESSI hard X-ray (HXR) data. We found
  good temporal correlations between the derived time profiles and
  observed HXR flux. Furthermore, it was confirmed that equal shares of
  positive and negative magnetic flux participated in the reconnection
  process. The findings indicate that the 2D reconnection model is
  applicable to the analysed flare.

---------------------------------------------------------
Title: Analysis of the Flare Wave Associated with the 3B/X3.8 Flare
    of January 17, 2005
Authors: Thalmann, J. K.; Veronig, A. M.; Temmer, M.; Vršnak, B.;
   Hanslmeier, A.
2007CEAB...31..187T    Altcode:
  The flare wave associated with the 3B/X3.8 flare and coronal mass
  ejection (CME) of January 17, 2005 are studied using imaging data
  in the Hα and EUV spectral channels. Due to the high-cadence Hα
  observations from Kanzelhöhe Solar Observatory (KSO), a distinct
  Moreton wave can be identified in ∼40 Hα frames over a period
  of ∼7 minutes. The associated coronal EIT wave is identifiable in
  only one EUV frame and appears close to the simultaneously observed
  Moreton wave front, indicating that they are closely associated
  phenomena. Beside the morphology of the wave across the solar disc
  (covering an angular extend of ∼130°), the evolution in different
  directions is studied to analyse the influence of a coronal hole (CH)
  on the wave propagation. The Moreton wave shows a decelerating character
  which can be interpreted in terms of a freely propagating fast-mode MHD
  shock. The parts of the wave front moving towards the CH show a lower
  initial and mean speed, and a greater amount of deceleration than the
  segments moving into the undisturbed direction. This is interpreted
  as the tendency of high Alfvén velocity regions to influence the
  propagation of wave packets.

---------------------------------------------------------
Title: Solar Rotation Velocity Determined by Coronal Bright Points -
    New Data and Analysis
Authors: Mulec, M.; Brajša, R.; Wöhl, H.; Hanslmeier, A.; Vršnak,
   B.; Ruždjak, V.; Hochedez, J. -F.; Engler, J.
2007CEAB...31....1M    Altcode:
  Full-disc solar images obtained with the Extreme Ultraviolet Imaging
  Telescope on board the Solar and Heliospheric Observatory were used
  to analyse solar differential rotation determined by tracing coronal
  bright points. Rotation velocity residuals, meridional motions and
  their relationship are investigated for a new data set from October
  1, 1999 to March 31, 2000. Further we take care for the evolution
  of the single structures, dividing them into Point-Like-Structures,
  Small Loops and Small Active Regions and analysing their variation in
  intensity and size.

---------------------------------------------------------
Title: Helical Eruptive Prominence Associated with a Pair of
    Overlapping CMEs on 21 April 2001
Authors: Ali, Syed Salman; Uddin, Wahab; Chandra, Ramesh; Mary, D. L.;
   Vršnak, Bojan
2007SoPh..240...89A    Altcode:
  The eruption of limb prominence on 21 April 2001 associated with
  two coronal mass ejections (CMEs) is investigated. Hα images
  reveal two large-scale eruptions (a prominence body and a southern
  foot-point arch), both showing helical internal structure. These two
  eruptions are found to be spatially and temporally associated with
  the corresponding CMEs. The kinematics and the study of geometrical
  parameters of the prominence show that the eruption was quite impulsive
  (with peak acceleration ≈470 m s<SUP>−2</SUP>) and has taken place
  for relatively low pitch angle of helical threads, not exceeding tan
  θ≈1.2. The stability criteria of the prominence are revisited in
  the light of the model of Vršnak (1990, Solar Phys.129, 295) and the
  analysis shows that the eruption violates the instability criteria of
  that model. Finally, the energy stored in the prominence circuit and
  the energies (kinetic, potential, and magnetic) of the associated CMEs
  are estimated and it is found that there was enough energy stored in
  the prominence to drive the two CMEs.

---------------------------------------------------------
Title: Spatial Restriction to HXR Footpoint Locations by Reconnection
    Site Geometries
Authors: Temmer, M.; Vršnak, B.; Veronig, A.; Miklenic, M.
2007CEAB...31...49T    Altcode: 2007astro.ph..1203T
  It is assumed that HXR sources map to the primary energy release site in
  flares where particle acceleration occurs. Strong HXR sources are mostly
  observed at confined regions along the reconnecting magnetic arcade. We
  make a general approach on how the geometry of the reconnecting current
  sheet (CS) may influence the strength and localization of observed HXR
  sources. For this we use results from an analysis on the 3B/X3.8 flare
  on January 17, 2005 (Temmer et al., 2007), as well as measurements from
  the associated CME. Due to the close match of the CME acceleration
  profile and the flare HXR flux, we suppose that the CME might play a
  certain role in modifying the geometry of the CS (“symmetric” versus
  “asymmetric” vertically stretched CS). This could be the driver for
  “guiding” the accelerated particles to confined areas along the
  flaring arcade and might explain the spatially limited occurrence of
  strong HXR sources in comparison to elongated ribbons as seen in Hα
  and UV.

---------------------------------------------------------
Title: Reconnection and energy release rates in a two-ribbon flare
Authors: Miklenic, C. H.; Veronig, A. M.; Vršnak, B.; Hanslmeier, A.
2007A&A...461..697M    Altcode:
  Aims:The aim of this study was to derive the local reconnection
  rate (coronal electric field) and the global reconnection rate
  (magnetic flux change rate), as well as the energy release rate
  (Poynting flux), in a two-ribbon flare from chromospheric/photospheric
  observations. Furthermore, we tested whether equal shares of positive
  and negative magnetic flux are involved in the flare process. <BR
  />Methods: A well-observed GOES M3.9 two-ribbon flare was analyzed. The
  required observables (ribbon expansion velocity, newly brightened area,
  and magnetic field strength at the ribbon front) were extracted from
  the TRACE 1600 Å and Kanzelhöhe Hα image time series, and a SOHO
  MDI magnetogram. Furthermore, the ratio of the converted positive
  vs. negative magnetic flux was determined. Both RHESSI hard X-ray
  20-60 keV full-disk time profiles and subregion time profiles derived
  from a time series of RHESSI images in the same energy range were used
  as independent, observable proxies for the energy release rate. The
  RHESSI images were also used to localize the sites where the bulk
  of the energy was deposited by fast electrons. <BR />Results: We
  found good temporal correlations between the derived time profiles
  (local and global reconnection rate, Poynting flux) and observed
  HXR flux. The local reconnection-rate peak values ranged from 2.7 {V
  cm<SUP>-1</SUP>} to 11.8 {V cm<SUP>-1</SUP>}, whereas the positive
  and the negative magnetic flux covered by the flare emission were
  equal within 5-10%. <BR />Conclusions: .The results indicate that
  the local reconnection rate, the global reconnection rate, and the
  energy release rate in a simple two-ribbon flare can be derived from
  chromospheric/photospheric observations. Furthermore, it was confirmed
  that equal shares of positive and negative magnetic flux participated
  in the reconnection process.

---------------------------------------------------------
Title: Recent Research: Large-scale Disturbances, their Origin
    and Consequences
Authors: Mann, Gottfried; Vršnak, Bojan
2007LNP...725..203M    Altcode:
  This article gives a flavour of recent research dedicated to the
  large-scale coronal disturbances and the related interplanetary
  phenomena. The discussions include the take-off and propagation of
  coronal mass ejections (CMEs); the CME-flare relationship; the origin
  and propagation of shocks; the role of flares, CMEs, and shocks in
  particle acceleration; radio signatures of CMEs and shocks; coronal
  and IP plasma diagnostics offered by the radio emission excited by
  these phenomena.

---------------------------------------------------------
Title: Energy Release Rates along Hα Flare Ribbons and the Location
    of Hard X-Ray Sources
Authors: Temmer, M.; Veronig, A. M.; Vršnak, B.; Miklenic, C.
2007ApJ...654..665T    Altcode:
  Local reconnection and energy release rates for an X3.8 flare that
  occurred on 2005 January 17 are derived. In particular, we distinguish
  between Hα flare ribbon segments that were accompanied by RHESSI
  hard X-ray (HXR) footpoints and those without HXRs. We find that the
  reconnection and energy release rates are not uniform along the flare
  ribbons but much larger at the locations where the HXR footpoints are
  observed. The difference is about 2 orders of magnitude in the case of
  the energy release rates and 1 order of magnitude for the reconnection
  rates (with peak values up to 8 kV m<SUP>-1</SUP>). These differences
  are enough to explain the different flare morphologies typically
  observed in HXRs (compact footpoints) and Hα/UV (extended ribbons)
  by the limited dynamic range of present HXR instruments. Our results
  are consistent with a scenario in which the electrons are accelerated
  primarily along a certain subsystem of magnetic loops as outlined by
  the HXR footpoints, and only a minor fraction (for the 2005 January
  17 flare estimated to be about 1/15) go into the large flare arcade
  outlined by the Hα ribbons and EUV postflare loops.

---------------------------------------------------------
Title: MHD Waves and Shocks Generated during Magnetic Field
    Reconnection
Authors: Bárta, M.; Karlický, M.; Vršnak, B.; Goossens, M.
2007CEAB...31..165B    Altcode:
  We use a 2D MHD model of magnetic field reconnection to investigate
  if and how bursts of reconnection activity, changes of the magnetic
  field and shock wave generation are related. We found that major
  bursts of power dissipated into Joule heat occur during topological
  transitions of the magnetic field structure. These bursts are followed
  by shocks and waves. Along the plasma outflow jet not only MHD waves,
  but also ion-sound shocks are formed. After the phase of more or
  less quiet reconnection (Petschek-type) the tearing mode produces
  plasmoids. The interactions of these plasmoids are associated with
  further bursts of the reconnection activity and a complex structure
  of shock waves. Finally, all these processes are discussed as possible
  sources of various radio bursts.

---------------------------------------------------------
Title: Millisecond solar radio bursts in the metric wavelength range
Authors: Magdalenić, J.; Hillaris, A.; Zlobec, P.; Vršnak, B.
2006AIPC..848..224M    Altcode: 2010arXiv1009.4477M
  A study and classification of super-short structures (SSSs) recorded
  during metric type IV bursts is presented. The most important property
  of SSSs is their duration, at half power ranging from 4-50 ms, what is
  up to 10 times shorter than spikes at corresponding frequencies. The
  solar origin of the SSSs is confirmed by one-to-one correspondence
  between spectral recordings of Artemis-IV<SUP>1</SUP> and high time
  resolution single frequency measurements of the TSRS<SUP>2</SUP>. <P
  />We have divided the SSSs in the following categories: <P
  />1. Broad-Band SSSs: They were partitioned in two subcategories, the
  SSS-Pulses and Drifting SSSs; <P />2. Narrow-band: They appear either
  as Spike-Like SSSs or as Patch-Like SSSs; <P />3. Complex SSS: They
  consist of the absorption-emission segments and were morphologically
  subdivided into Rain-drop Bursts (narrow-band emission head and a
  broad-band absorption tail) and Blinkers.

---------------------------------------------------------
Title: Interaction of a Moreton/EIT Wave and a Coronal Hole
Authors: Veronig, Astrid M.; Temmer, Manuela; Vršnak, Bojan; Thalmann,
   Julia K.
2006ApJ...647.1466V    Altcode: 2006astro.ph..4613V
  We report high-cadence Hα observations of a distinct Moreton wave
  observed at Kanzelhöhe Solar Observatory associated with the 3B/X3.8
  flare and coronal mass ejection (CME) event of 2005 January 17. The
  Moreton wave can be identified in about 40 Hα frames over a period of
  7 minutes. The EIT wave is observed in only one frame, but the derived
  propagation distance is close to that of the simultaneously measured
  Moreton wave fronts, indicating that they are closely associated
  phenomena. The large angular extent of the Moreton wave allows us to
  study the wave kinematics in different propagation directions with
  respect to the location of a polar coronal hole (CH). In particular, we
  find that the wave segment whose propagation direction is perpendicular
  to the CH boundary (“frontal encounter”) is stopped by the CH, which
  is in accordance with observations reported from EIT waves. However,
  we also find that at a tongue-shaped edge of the coronal hole, where
  the front orientation is perpendicular to the CH boundary (the wave
  “slides along” the boundary), the wave signatures can be found up
  to 100 Mm inside the CH. These findings are briefly discussed in the
  frame of recent modeling results.

---------------------------------------------------------
Title: Reconnection and Energy Release Rates in aTwo-Ribbon Flare
Authors: Miklenic, Christiane H.; Veronig, A. M.; Vrsnak, B.
2006SPD....37.0801M    Altcode: 2006BAAS...38..230M
  We tried to verify whether the local reconnection rate (coronal
  electric field) and the global reconnection rate (magnetic flux
  change rate) as well as the energy release rate (Poynting flux) in
  a two-ribbon flare can be derived from chromospheric/photospheric
  observations. Furthermore, we tested whether equal shares of positive
  and negative magnetic flux are involved in the flare process.A
  well observed GOES M3.9 two-ribbon flare was analyzed. The required
  observables (ribbon expansion velocity, magnetic field strength at the
  ribbon front, and newly brightened area) were extracted from TRACE
  1600 Å and Kanzelhöhe H-alpha image time series, and a SOHO MDI
  magnetogram, respectively. Furthermore, the ratio of the converted
  positive vs. negative magnetic flux was determined. RHESSI Hard X-ray
  20 - 60 keV full-disk time profiles as well as subregion imaging light
  curves derived from a time series of RHESSI images in the same energy
  range, were used as independent, observable proxies of the reconnection
  and the energy release rate, respectively. The RHESSI images were also
  used to localize the sites where the bulk of the energy was deposited
  by fast electrons.We found good temporal correlations between derived
  time profiles (local and global reconnection rate, Poynting flux) and
  observed HXR flux. The local reconnection rate peak values ranged from
  1.4 V/cm to 4.6 V/cm, and the ratio of converted positive vs. negative
  magnetic flux deviated from the theoretically expected value by
  only 5 - 10%.The results indicate that the local reconnection rate,
  the global reconnection rate as well as the energy release rate in a
  simple two-ribbon flare can be derived from chromospheric/photospheric
  observations. Furthermore, it was confirmed that equal shares of
  positive and negative magnetic flux participated in the reconnection
  process.This work is supported by the Austrian ‘Fonds zur Förderung
  der wissenschaftlichen Forschung’ under project P15344.

---------------------------------------------------------
Title: Classification and Properties of Supershort Solar Radio Bursts
Authors: Magdalenić, J.; Vršnak, B.; Zlobec, P.; Hillaris, A.;
   Messerotti, M.
2006ApJ...642L..77M    Altcode:
  Characteristics of supershort structures (SSSs) occurring in the
  metric solar type IV radio bursts are described. The most important
  property of SSSs is their duration, which, at half-power, ranges from
  4 to 60 ms and is thus much shorter than generally expected for the
  bursts in the metric range. The comparison of the distributions of SSS
  durations with those of the spikes confirms that these are completely
  different classes of bursts. Our analysis is focused on the frequency
  range 200-450 MHz, providing us with the one-to-one identification
  of individual SSSs in single-frequency records of the INAF-Trieste
  Astronomical Observatory (Italy) and in the high-resolution spectral
  data of Artemis IV (Greece). The analysis reveals a number of different
  bursts that are classified as simple broadband, simple narrowband, and
  complex SSSs. The diversity of SSSs has a resemblance to the variety
  of the well-known metric radio bursts characterized by a 1 s timescale.

---------------------------------------------------------
Title: Shrinking and Cooling of Flare Loops in a Two-Ribbon Flare
Authors: Vršnak, Bojan; Temmer, Manuela; Veronig, Astrid; Karlický,
   Marian; Lin, Jun
2006SoPh..234..273V    Altcode:
  We analyze the evolution of the flare/postflare-loop system in the
  two-ribbon flare of November 3, 2003, utilizing multi-wavelength
  observations that cover the temperature range from several tens of
  MK down to 10<SUP>4</SUP> K. A non-uniform growth of the loop system
  enables us to identify analogous patterns in the height-time, h(t),
  curves measured at different temperatures. The "knees," "plateaus,"
  and "bends" in a higher-temperature curve appear after a certain time
  delay at lower heights in a lower-temperature curve. We interpret such
  a shifted replication as a track of a given set of loops (reconnected
  field lines) while shrinking and cooling after being released from the
  reconnection site. Measurements of the height/time shifts between h(t)
  curves of different temperatures provide a simultaneous estimate of
  the shrinkage speed and cooling rate in a given temperature domain,
  for a period of almost ten hours after the flare impulsive phase. From
  the analysis we find the following: (a) Loop shrinkage is faster at
  higher temperatures - in the first hour of the loop-system growth,
  the shrinkage velocity at 5 MK is 20 - 30 km s<SUP>−1</SUP>, whereas
  at 1 MK it amounts to 5 km s<SUP>−1</SUP>; (b) Shrinking becomes
  slower as the flare decays - ten hours after the impulsive phase,
  the shrinkage velocity at 5 MK becomes 5 km s<SUP>−1</SUP>; (c) The
  cooling rate decreases as the flare decays - in the 5 MK range it is
  1 MK min<SUP>−1</SUP> in the first hour of the loop-system growth,
  whereas ten hours later it decreases to 0.2 MK min<SUP>−1</SUP>;
  (d) During the initial phase of the loop-system growth, the cooling
  rate is larger at higher temperatures, whereas in the late phases
  the cooling rate apparently does not depend on the temperature; (e)
  A more detailed analysis of shrinking/cooling around one hour after
  the impulsive phase reveals a deceleration of the loop shrinkage,
  amounting to ā ≈ 10 m s<SUP>−2</SUP> in the T &lt; 5 MK range;
  (f) In the same interval, conductive cooling dominates down to T ≈
  3 MK, whereas radiation becomes dominant below T ≈ 2 MK; (g) A few
  hours after the impulsive phase, radiation becomes dominant across the
  whole T &lt; 5 MK range. These findings are compared with results of
  previous studies and discussed in the framework of relevant models.

---------------------------------------------------------
Title: Multi-wavelength study of coronal waves associated with the
    CME-flare event of 3 November 2003
Authors: Vršnak, B.; Warmuth, A.; Temmer, M.; Veronig, A.;
   Magdalenić, J.; Hillaris, A.; Karlický, M.
2006A&A...448..739V    Altcode:
  The large flare/CME event that occurred close to the west solar limb on
  3 November 2003 launched a large-amplitude large-scale coronal wave that
  was observed in Hα and Fe xii 195 Å spectral lines, as well as in the
  soft X-ray and radio wavelength ranges. The wave also excited a complex
  decimeter-to-hectometer type II radio burst, revealing the formation of
  coronal shock(s). The back-extrapolation of the motion of coronal wave
  signatures and the type II burst sources distinctly marks the impulsive
  phase of the flare (the hard X-ray peak, drifting microwave burst,
  and the highest type III burst activity), favoring a flare-ignited
  wave scenario. On the other hand, comparison of the kinematics of
  the CME expansion with the propagation of the optical wave signatures
  and type II burst sources shows a severe discrepancy in the CME-driven
  scenario. However, the CME is quite likely associated with the formation
  of an upper-coronal shock revealed by the decameter-hectometer type II
  burst. Finally, some six minutes after the launch of the first coronal
  wave, another coronal disturbance was launched, exciting an independent
  (weak) decimeter-meter range type II burst. The back-extrapolation
  of this radio emission marks the revival of the hard X-ray burst,
  and since there was no CME counterpart, it was clearly ignited by the
  new energy release in the flare.

---------------------------------------------------------
Title: Coronal Mass Ejection of 28 June 2000: Coupling of the CME
    Evolution and the Flare Energy Release
Authors: Maričić, D.; Roša, D.; Vršnak, B.
2006SunGe...1a..35M    Altcode:
  We study the initiation and development of the limb Coronal Mass
  Ejection (CME) of 28 Jun 2000, utilizing observations from Mauna
  Loa Solar Observatory (MLSO), the Solar and Heliospheric Observatory
  (SOHO), the Geostationary Operational Environmental Satellite (GOES)
  and Yohkoh. Also, we analyze the relation between dynamics of the
  Coronal Mass Ejection (CME) and the energy release in the associated
  flare. The basic structure of the CME (prominence imbedded in bright
  coronal arcade) is clearly recognizable already in the low corona during
  the pre-eruption phase of slow rise. This provided measurements of
  kinematics of various features from the very beginning of the eruption
  up to the post-acceleration phase which was followed up to 32 solar
  radii. Such events are observed only occasionally, and are of great
  importance for the comprehension of the nature of forces driving
  CMEs. The acceleration maximum was attained at the radial distance
  of 1.45 solar radii from the Sun's center and ceased beyond 4 solar
  radii. The acceleration phase was synchronized with the impulsive
  phase of the associated two-ribbon flare. Observations provide clear
  evidence that the CME eruption caused a global restructuring of the
  magnetic field in the outer and inner corona.

---------------------------------------------------------
Title: X-ray sources and magnetic reconnection in the X3.9 flare of
    2003 November 3
Authors: Veronig, A. M.; Karlický, M.; Vršnak, B.; Temmer, M.;
   Magdalenić, J.; Dennis, B. R.; Otruba, W.; Pötzi, W.
2006A&A...446..675V    Altcode:
  Context: .Recent RHESSI observations indicate an apparent altitude
  decrease of flare X-ray loop-top (LT) sources before changing to the
  commonly observed upward growth of the flare loop system.<BR /> Aims:
  .We performed a detailed study of the LT altitude decrease for one well
  observed flare in order to find further hints on the physics of this
  phenomenon and how it is related to the magnetic reconnection process in
  solar flares.<BR /> Methods: .RHESSI X-ray source motions in the 2003
  November 3, X3.9 flare are studied together with complementary data
  from SXI, EIT, and Kanzelhöhe Hα. We particularly concentrate on the
  apparent altitude decrease of the RHESSI X-ray LT source early in the
  flare and combine kinematical and X-ray spectral analysis. Furthermore,
  we present simulations from a magnetic collapsing trap model embedded
  in a standard 2-D magnetic reconnection model of solar flares.<BR />
  Results: .We find that at higher photon energies the LT source is
  located at higher altitudes and shows higher downward velocities
  than at lower energies. The mean downward velocities range from
  14 km s<SUP>-1</SUP> in the RHESSI 10-15 keV energy band to 45 km
  s<SUP>-1</SUP> in the 25-30 keV band. For this flare, the LT altitude
  decrease was also observed by the SXI instrument with a mean speed of
  12 km s<SUP>-1</SUP>. RHESSI spectra indicate that during the time
  of LT altitude decrease the emission of the LT source is thermal
  bremsstrahlung from a "superhot" plasma with temperatures increasing
  from 35 MK to 45 MK and densities of the order of 10<SUP>10</SUP>
  cm<SUP>-3</SUP>. The temperature does not significantly increase
  after this early (pre-impulsive superhot LT) phase, whereas the
  LT densities increase to a peak value of (3-4) × 10<SUP>11</SUP>
  cm<SUP>-3</SUP>.<BR /> Conclusions: .Modeling of a collapsing magnetic
  trap embedded in a standard 2D magnetic reconnection model can reproduce
  the key observational findings in case that the observed emission is
  thermal bremsstrahlung from the hot LT plasma. This agrees with the
  evaluated RHESSI spectra for this flare.

---------------------------------------------------------
Title: Model of Motion of the X-Ray Loop-Top Source at the Beginning
    of Cusp-Type Flares
Authors: Karlický, M.; Veronig, A.; Vršnak, B.
2006CEAB...30...85K    Altcode:
  A model with a 1-D collapsing magnetic trap is proposed for
  an explanation of the motion of the X-ray loop-top source at the
  beginning of cusp-type flares. Considering plasma heating due to the
  betatron mechanism an analytic formula for the temporal and spatial
  evolution of heated plasma temperature in the trap is derived. Using
  the formula and the relation for thermal bremsstrahlung flux, the
  time evolution of the X-ray intensity profile in the trap is computed
  numerically. The model explains not only the downward motion of the
  X-ray loop-top source observed at the beginning of cusp-type flares,
  but also the upward motion which follows.

---------------------------------------------------------
Title: New Families of Super Short Radio Bursts (Abstract)
Authors: Magdalenić, J.; Vrsnak, B.; Zlobec, P.; Hillaris, A.
2006pre6.conf..399M    Altcode: 2006pre4.conf..399M
  Several new families of super-short Solar radio features occurring
  in type IV bursts are presented. We discovered them in the high time
  resolution data (1 ms) recorded by the multichannel radiopolarimeter
  of the Trieste Astronomical Observatory. The reliability of these
  super-short structures (SSSs) is confirmed by one-to-one identification
  of individual SSS events in the corresponding Artemis-IV (University
  of Athens) spectral recordings. The most important characterists of
  SSSs is that they are faster then spikes, up to now considered the
  shortest Solar radio bursts [Guedel and Benz, A&amp;A 231, 1, 202-212,
  1990]. SSSs are 1-6 times shorter than the spikes, and it seems
  that their duration is not frequency dependent. Another distinction
  in respect to spikes is a stochastic change of the polarization
  degree (0-100%), sometimes also including the change of the sense of
  polarization within a given group of SSSs. Analysis of the spectral
  and single-frequency morphology reveals at least 3 distinct categories:
  "rain drops", broad-band SSSs, and spike-like SSSs. It seems that some
  subclasses also exist.

---------------------------------------------------------
Title: Theoretical and Observational Features of Magnetic Reconnection
Authors: Biernat, H. K.; Semenov, V. S.; Penz, T.; Miklenic, C.;
   Veronig, A.; Hanslmeier, A.; Vršnak, B.; Heyn, M. F.; Ivanov, I. B.;
   Ivanova, V. V.; Kiehas, S. A.; Langmayr, D.
2006CEAB...30...75B    Altcode:
  We present general solutions of the time--dependent <P />Petschek--type
  model of magnetic reconnection for a compressible <P />plasma. The
  disruption of a tangential discontinuity because of <P />a localized
  decrease of the resistivity leads to the generation <P />of several
  MHD wave modes. By solving the Riemann problem, the <P />behavior of
  these modes can be visualized. Additionally, <P />disturbances of the
  ambient plasma environment by the propagating <P />shock structures
  can be modeled. As an observational feature, the <P />determination
  of the reconnection rate in a two--ribbon flare is <P />presented.

---------------------------------------------------------
Title: Forces governing coronal mass ejections
Authors: Vršnak, B.
2006AdSpR..38..431V    Altcode:
  Kinematics of CMEs is analyzed to get an insight into the properties
  of forces partaking in the eruption. It is demonstrated that the
  Lorentz force plays a dominant role within a distance of a few
  solar radii. In the distance range 1 30 solar radii, the inferred
  values of the Lorentz-force acceleration a<SUB>L</SUB> on average
  decrease with the heliocentric distance roughly as a<SUB>L</SUB> ∝
  R<SUP>-2</SUP>. Generally, the values are found to be in the range g ≲
  a<SUB>L</SUB> &lt; 30g, where g(R) is the acceleration of gravity. In
  fast events, the aerodynamic drag is comparable to the Lorentz force,
  and on average also decreases with the distance. However, the decrease
  is more gradual, so the drag becomes essential in the upper corona
  and interplanetary space. Inspecting the CME flare relationship it is
  demonstrated that the reconnection beneath the CME plays an active role
  in the CME acceleration. Statistically, the CME speeds are correlated
  with the importance of the associated flare. The distribution of
  non-flare CME speeds is very similar to that of CMEs associated with
  flares of the soft X-ray importance C, and includes a considerable
  fraction of fast events. This implies that the concept of two distinct
  classes of CMEs (flare and non-flare) should be reformulated.

---------------------------------------------------------
Title: X-Ray Sources and Magnetic Reconnection in AN X-Class Flare
Authors: Veronig, A. M.; Vršnak, B.; Karlický, M.; Temmer, M.;
   Magdalenić, J.; Dennis, B. R.; Otruba, W.; Pötzi, W.
2005ESASP.600E..32V    Altcode: 2005ESPM...11...32V; 2005dysu.confE..32V
  No abstract at ADS

---------------------------------------------------------
Title: Properties of Very Short Duration Solar Radio Bursts
Authors: Magdalenić, J.; Vršnak, B.; Zlobec, P.; Aurass, H.
2005ESASP.600E.131M    Altcode: 2005dysu.confE.131M; 2005ESPM...11..131M
  No abstract at ADS

---------------------------------------------------------
Title: Wave Phenomena Associated with the X3.8 Flare/cme of
    17-JAN-2005
Authors: Temmer, M.; Veronig, A.; Vršnak, B.; Thalmann, J.;
   Hanslmeier, A.
2005ESASP.600E.144T    Altcode: 2005ESPM...11..144T; 2005dysu.confE.144T
  No abstract at ADS

---------------------------------------------------------
Title: Spatial Distribution and North-South Asymmetry of Coronal
    Bright Points from Mid-1998 to Mid-1999
Authors: Brajša, R.; Wöhl, H.; Vršnak, B.; Rušdjak, V.; Clette,
   F.; Hochedez, J. -F.; Verbanac, G.; Temmer, M.
2005SoPh..231...29B    Altcode:
  Full-disc full-resolution (FDFR) solar images obtained with the Extreme
  Ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric
  Observatory (SOHO) were used to analyse the centre-to-limb function and
  latitudinal distribution of coronal bright points. The results obtained
  with the interactive and the automatic method, as well as for three
  subtypes of coronal bright points for the time period 4 June 1998 to 22
  May 1999 are presented and compared. An indication of a two-component
  latitudinal distribution of coronal bright points was found. The
  central latitude of coronal bright points traced with the interactive
  method lies between 10<SUP>∘</SUP> and 20<SUP>∘</SUP>. This is
  closer to the equator than the average latitude of sunspots in the
  same period. Possible implications for the interpretation of the
  solar differential rotation are discussed. In the appendix, possible
  differences between the two solar hemispheres are analysed. More coronal
  bright points were present in the southern solar hemisphere than in
  the northern one. This asymmetry is statistically significant for the
  interactive method and not for the automatic method. The visibility
  function is symmetrical around the central meridian.

---------------------------------------------------------
Title: The CME-flare relationship: Are there really two types of CMEs?
Authors: Vršnak, B.; Sudar, D.; Ruždjak, D.
2005A&A...435.1149V    Altcode:
  We present a statistical analysis of 545 flare-associated CMEs and 104
  non-flare CMEs observed in the heliocentric distance range 2-30 solar
  radii. We found that both data sets show quite similar characteristics,
  contradicting the concept of two distinct (flare/non-flare) types of
  CMEs. In both samples there is a significant fraction of CMEs showing
  a considerable acceleration or deceleration and both samples include a
  comparable ratio of fast and slow CMEs. We present kinematical curves of
  several fast non-flare CMEs moving at a constant speed or decelerating,
  i.e., behaving as expected for flare-associated CMEs. Analogously,
  we identified several slow flare-CMEs showing the acceleration peak
  beyond a height of 3 solar radii. On the other hand, it is true that
  CMEs associated with major flares are on average faster and broader than
  non-flare CMEs and small-flare CMEs. There is a well-defined correlation
  between the CME speed and the importance of the associated flare. In
  this respect, the non-flare CMEs show characteristics similar to CMEs
  associated with flares of soft X-ray class B and C, which is indicative
  of a "continuum" of events rather than supporting the existence of
  two distinct CME classes. Furthermore, we inferred that CMEs whose
  source region cannot be identified with either flares or eruptive
  prominences are on average slowest. The results indicate that the
  magnetic reconnection taking place in the current sheet beneath the
  CME significantly influences the CME dynamics.

---------------------------------------------------------
Title: Broadband Metric-Range Radio Emission Associated with a
    Moreton/EIT Wave
Authors: Vršnak, B.; Magdalenić, J.; Temmer, M.; Veronig, A.;
   Warmuth, A.; Mann, G.; Aurass, H.; Otruba, W.
2005ApJ...625L..67V    Altcode:
  We present the evolution and kinematics of a broadband radio source
  that propagated collaterally with an Hα/EIT wave, linking it with the
  type II burst that was excited higher up in the corona. The NRH wave
  emission extended from the frequency f~327 to f&lt;151 MHz and was
  considerably weaker than the flare-related type IV burst. The emission
  centroid propagated at a height of 0-200 Mm above the solar limb and
  was intensified when the disturbance passed over enhanced coronal
  structures. We put forward the ad hoc hypothesis that the NRH wave
  signature is optically thin gyrosynchrotron emission excited by the
  passage of the coronal MHD fast-mode shock. The identification of radio
  emission associated with the coronal wave front is important since it
  offers us new diagnostic information that could provide us with better
  insight into the physical conditions in the disturbance itself.

---------------------------------------------------------
Title: Terminology of Large-Scale Waves in the Solar Atmosphere
Authors: Vršnak, Bojan
2005EOSTr..86..112V    Altcode:
  This is the fourth in a series of essays on terms used in
  solar-terrestrial physics that are thought to be in need of
  clarification. Terms are identified and essays are commissioned by
  a committee chartered by Division II (Sun and Heliosphere) of the
  International Astronomical Union. Terminology Committee members include
  Ed Cliver (chair), Jean-Louis Bougeret, Hilary Cane, Takeo Kosugi, Sara
  Martin, Rainer Schwenn, and Lidia van Driel-Gestelyi. Authors are asked
  to review the origins of terms and their current usage/misusage. The
  goals are to inform the community and to open a discussion. The
  following article by Bojan Vršnak focuses on terms used to describe
  large-scale waves in the solar atmosphere, an area of research that
  has been given great impetus by the images of waves from the Extreme
  ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric
  Observatory (SOHO). The committee welcomes suggestions for other terms
  to address in this forum.

---------------------------------------------------------
Title: 2 1/2 -D compressible reconnection model
Authors: Skender, M.; Vršnak, B.
2005ASSL..320..167S    Altcode: 2005smp..conf..167S
  No abstract at ADS

---------------------------------------------------------
Title: Solar Flares — Observations and Theory
Authors: Vršnak, Bojan
2005ASSL..320...27V    Altcode: 2005smp..conf...27V
  No abstract at ADS

---------------------------------------------------------
Title: Exact Solution of Jump Relations at Discontinuities in a
    Two-And-Half-Dimensional Compressible Reconnection Model
Authors: Skender, Marina; Vršnak, Bojan; Martinis, Mladen
2005IAUS..226..274S    Altcode:
  Two-and-half-dimensional reconnection is examined for a compressible
  plasma: Exact solution of jump relations in the system of
  discontinuities is used to investigate how the outflowing jet and the
  conditions in the intermediate region depend on the characteristics of
  the inflow. The most significant implications concerning large-scale
  eruptive phenomena of solar atmosphere are presented.

---------------------------------------------------------
Title: Properties of Type IV Radio Bursts with Periodical Fine
    Structures
Authors: Magdalenić, J.; Vršnak, B.; Zlobec, P.; Messerotti, M.;
   Temmer, M.
2005ASSL..320..259M    Altcode: 2005smp..conf..259M
  No abstract at ADS

---------------------------------------------------------
Title: The Acceleration-Velocity Relationship in 5000 LASCO-CME's
Authors: Ruždjak, D.; Vršnak, B.; Sudar, D.
2005ASSL..320..195R    Altcode: 2005smp..conf..195R
  No abstract at ADS

---------------------------------------------------------
Title: 2 1/2-Dimensional Reconnection Model and Energy Release in
    Solar Flares
Authors: Vršnak, Bojan; Skender, Marina
2005SoPh..226...97V    Altcode:
  We employ a 2 1/2-dimensional reconnection model to analyse different
  aspects of the energy release in two-ribbon flares. In particular,
  we investigate in which way the systematic change of inflow region
  variables, associated with the vertical elongation of current sheet,
  affects the flare evolution. It is assumed that as the transversal
  magnetic field decreases, the ambient plasma-to-magnetic pressure ratio
  increases, and the reconnection rate diminishes. As the transversal
  field decreases due to the arcade stretching, the energy release
  enhances and the temperature rises. Furthermore, the magnetosonic
  Mach number of the reconnection outflow increases, providing the
  formation of fast mode standing shocks above the flare loops and
  below the erupting flux rope. Eventually, in the limit of a very
  small transversal field the reconnection becomes turbulent due to
  a highly non-linear response of the system to small fluctuations of
  the transversal field. The turbulence results in the energy release
  fragmentation which increases the release efficiency, and is likely
  to be responsible for the impulsive phase of the flare. On the other
  hand, as the current sheet stretches to larger heights, the ambient
  plasma-to-magnetic pressure ratio increases which causes a gradual
  decrease of the reconnection rate, energy release rate, and temperature
  in the late phase of flare. The described magnetohydrodynamical changes
  affect also the electron distribution function in space and time. At
  large reconnection rates (impulsive phase of the flare) the ratio of the
  inflow-to-outflow magnetic field strength is much smaller than at lower
  reconnection rates (late phase of the flare), i.e., the corresponding
  loss-cone angle becomes narrower. Consequently, in the impulsive phase
  a larger fraction of energized electrons can escape from the current
  sheet downwards to the chromosphere and upwards into the corona -
  the dominant flare features are the foot-point hard X-ray sources and
  type III radio bursts. On the other hand, at low reconnection rates,
  more particles stay trapped in the outflow region, and the thermal
  conduction flux becomes strongly reduced. As a result, a superhot
  loop-top, and above-the-loop plasma appears, as sometimes observed,
  to be a dominant feature of the gradual phase.

---------------------------------------------------------
Title: Loop-Top Altitude Decrease in an X-Class Flare
Authors: Veronig, A.; Vršnak, B.; Karlický, M.; Temmer, M.;
   Magdalenić, J.; Dennis, B. R.; Otruba, W.; Pötzi, W.
2005HvaOB..29..127V    Altcode:
  We study RHESSI X-ray source motions in the X3.9 flare of 2003 November
  3. Particular attention is drawn to the apparent altitude decrease
  of a distinct loop-top (LT) source at the early flare phase before
  then changing to the commonly observed upward expansion of the flare
  loop system. We obtain that the downward motion is more pronounced
  at higher X-ray energies (peak values up to 50 km s^{-1}) consistent
  with recent findings by Sui et al. (2004). RHESSI spectra indicate
  that the emission process in the LT source is thermal bremsstrahlung
  from a super hot plasma (∼40 MK) with high densities increasing from
  ∼10^{10} cm^{-3} early in the flare to several times 10^{11} cm^{-3}
  at the end of RHESSI observations.

---------------------------------------------------------
Title: Coronal Mass Ejection of 15 May 2001: II. Coupling of the
    Cme Acceleration and the Flare Energy Release
Authors: Vršnak, B.; Maričić, D.; Stanger, A. L.; Veronig, A.
2004SoPh..225..355V    Altcode:
  We analyze the relationship between the dynamics of the coronal mass
  ejection (CME) of 15 May 2001 and the energy release in the associated
  flare. The flare took place behind the east limb and was disclosed by a
  growing system of hot soft X-ray (SXR) loops that appeared from behind
  the limb around the onset of the rapid acceleration of the CME. The
  highly correlated behavior of the SXR light-curve derivative and the
  time profile of the CME acceleration reveals an intrinsic relationship
  between the CME dynamics and the flare energy release. Furthermore,
  we found that the CME acceleration peak occurs simultaneously with the
  fastest growth (100 km s<SUP>-1</SUP>) of X-ray loops, indicating that
  the reconnection plays an essential role in the eruption. Inspecting
  the CME/flare morphology we recognized in the Yohkoh-SXT images an
  oval feature that formed within the rising structure at the onset
  of the rapid acceleration phase, simultaneously with the appearance
  of the X-ray loops. The eruptive prominence was imbedded within
  the lower half of the oval, suggestive of a flux-rope/prominence
  magnetic configuration. We interpret the observed morphological
  evolution in terms of a reconnection process in the current sheet that
  presumably formed below the erupting flux-rope at the onset of the CME
  acceleration. Measurements of the tip-height of the cusped X-ray loop
  system and the height of the lower edge of the oval, enable us to trace
  the stretching of the current sheet. The initial distance between the
  oval and the loops amounted to 35 - 40 Mm. In about 1 h the inferred
  length of the current sheet increased to 150 - 200 Mm, which corresponds
  to a mean elongation speed of 35 - 45 km s<SUP>-1</SUP>. The results
  are discussed in the framework of CME models that include the magnetic
  reconnection below the erupting flux-rope.

---------------------------------------------------------
Title: Coronal Mass Ejection of 15 May 2001: I. Evolution of
    Morphological Features of the Eruption
Authors: Maričić, D.; Vršnak, B.; Stanger, A. L.; Veronig, A.
2004SoPh..225..337M    Altcode:
  We study the initiation and development of the limb coronal mass
  ejection (CME) of 15 May 2001, utilizing observations from Mauna Loa
  Solar Observatory (MLSO), the Solar and Heliospheric Observatory (SOHO),
  and Yohkoh. The pre-eruption images in various spectral channels show
  a quiescent prominence imbedded in the coronal void, being overlaid
  by the coronal arch. After the onset of rapid acceleration, this
  three-element structure preserved its integrity and appeared in the
  MLSO MK-IV coronagraph field of view as the three-part CME structure
  (the frontal rim, the cavity, and the prominence) and continued its
  motion through the field of view of the SOHO/LASCO coronagraphs up
  to 30 solar radii. Such observational coverage allows us to measure
  the relative kinematics of the three-part structure from the very
  beginning up to the late phases of the eruption. The leading edge and
  the prominence accelerated simultaneously: the rapid acceleration of
  the frontal rim and the prominence started at approximately the same
  time, the prominence perhaps being slightly delayed (4 - 6 min). The
  leading edge achieved the maximum acceleration a<SUB>max</SUB>≈ 600
  ± 150 m s<SUP>−2</SUP> at a heliocentric distance 2.4 -2.5 solar
  radii, whereas the prominence reached a<SUB>max</SUB>≈ 380± 50 m
  s<SUP>−2</SUP>, almost simultaneously with the leading edge. Such a
  distinct synchronization of different parts of the CME provides clear
  evidence that the entire magnetic arcade, including the prominence,
  erupts as an entity, showing a kind of self-similar expansion. The
  CME attained a maximum velocity of v<SUB>max</SUB>≈ 1200 km
  s<SUP>−1</SUP> at approximately the same time as the peak of the
  associated soft X-ray flare. Beyond about 10 solar radii, the leading
  edge of the CME started to decelerate at a≈−20 m s<SUP>−2</SUP>,
  most likely due to the aerodynamic drag. The deceleration of the
  prominence was delayed for 10 -30 min, which is attributed to its
  larger inertia.

---------------------------------------------------------
Title: Kinematics of coronal mass ejections between 2 and 30 solar
    radii. What can be learned about forces governing the eruption?
Authors: Vršnak, B.; Ruždjak, D.; Sudar, D.; Gopalswamy, N.
2004A&A...423..717V    Altcode:
  Kinematics of more than 5000 coronal mass ejections (CMEs)
  measured in the distance range 2-30 solar radii is investigated. A
  distinct anticorrelation between the acceleration, a, and the
  velocity, v, is found. In the linear form, it can be represented
  as a=-k<SUB>1</SUB>(v-v<SUB>0</SUB>), where v<SUB>0</SUB>=400 km
  s<SUP>-1</SUP>, i.e., most of CMEs faster than 400 km s<SUP>-1</SUP>
  decelerate, whereas slower ones generally accelerate. After grouping
  CMEs into the width and mean-distance bins, it was found that the
  slope k<SUB>1</SUB> depends on these two parameters: k<SUB>1</SUB>
  is smaller for CMEs of larger width and mean-distance. Furthermore,
  the obtained CME subsets show distinct quadratic-form correlations,
  of the form a= -k<SUB>2</SUB> (v-v<SUB>0</SUB>)| v-v<SUB>0</SUB>|. The
  value of k<SUB>2</SUB> decreases with increasing distance and width,
  whereas v<SUB>0</SUB> increases with the distance and is systematically
  larger than the slow solar wind speed by 100-200 km s<SUP>-1</SUP>. The
  acceleration-velocity relationship is interpreted as a consequence of
  the aerodynamic drag. The excess of v<SUB>0</SUB> over the solar wind
  speed is explained assuming that in a certain fraction of events the
  propelling force is still acting in the considered distance range. In
  most events the inferred propelling force acceleration at 10 solar radii
  ranges between a<SUB>L</SUB>=0 and 10 m s<SUP>-2</SUP>, being on average
  smaller at larger distances. However, there are also events that show
  a<SUB>L</SUB>&gt;50 m s<SUP>-2</SUP>, as well as events indicating
  a<SUB>L</SUB>&lt;0. Implications for the interplanetary motion of
  CMEs are discussed, emphasizing the prediction of the 1 a.u. arrival
  time. <P />Appendices A and B are only available in electronic form
  at http://www.edpsciences.org

---------------------------------------------------------
Title: A multiwavelength study of solar flare waves. II. Perturbation
    characteristics and physical interpretation
Authors: Warmuth, A.; Vršnak, B.; Magdalenić, J.; Hanslmeier, A.;
   Otruba, W.
2004A&A...418.1117W    Altcode:
  The study of solar flare waves - globally propagating wave-like
  disturbances usually observed in Hα as Moreton waves - has recently
  come back into focus prompted by the observation of coronal waves in
  the EUV with the SOHO/EIT instrument (“EIT waves"), and in several
  additional wavelength channels. We study 12 flare wave events in
  order to determine their physical nature, using Hα, EUV, helium I,
  SXR and radioheliographic data. In the companion Paper I, we have
  presented the observational data and have discussed the morphology,
  spatial characteristics and the kinematics of the different flare
  wave signatures. The wavefronts observed in the various spectral bands
  were found to follow kinematical curves that are closely associated,
  implying that they are signatures of the same physical disturbance. In
  the present paper, we continue the study with a close examination of
  the evolution of the common perturbation that causes the different wave
  signatures, and with a detailed analysis of the metric type II radio
  bursts that were associated with all flare wave events. The basic
  characteristics of the waves are deceleration, perturbation profile
  broadening, and perturbation amplitude decrease. This behavior can
  be interpreted in terms of a freely propagating fast-mode MHD shock
  formed from a large-amplitude simple wave. It is shown that this
  scenario can account for all observed properties of the flare waves
  in the various spectral bands, as well as for the associated metric
  type II radio bursts.

---------------------------------------------------------
Title: A multiwavelength study of solar flare waves. I. Observations
    and basic properties
Authors: Warmuth, A.; Vršnak, B.; Magdalenić, J.; Hanslmeier, A.;
   Otruba, W.
2004A&A...418.1101W    Altcode:
  Propagating wave-like disturbances associated with solar flares -
  commonly observed in the chromosphere as Moreton waves - have been
  known for several decades. Recently, the phenomenon has come back into
  focus prompted by the observation of coronal waves with the SOHO/EIT
  instrument (“EIT waves"). It has been suggested that they represent
  the anticipated coronal counterpart to Moreton waves, but due to some
  pronounced differences, this interpretation is still being debated. We
  study 12 flare wave events in order to determine their physical nature,
  using Hα, EUV, He I 10 830 Å, SXR and radioheliographic data. The
  flare wave signatures in the various spectral bands are found to
  lie on closely associated kinematical curves, implying that they are
  signatures of the same physical disturbance. In all events, and at
  all wavelengths, the flare waves are decelerating, which explains
  the apparent “velocity discrepancy" between Moreton and EIT waves
  which has been reported by various authors. In this paper, the focus
  of the study is on the morphology, the spatial characteristics and the
  kinematics of the waves. The characteristics of the common perturbation
  which causes the wave signatures, as well as the associated type II
  radio bursts, will be studied in companion Paper II, and a consistent
  physical interpretation of flare waves will be given.

---------------------------------------------------------
Title: Height correction in the measurement of solar differential
    rotation determined by coronal bright points
Authors: Brajša, R.; Wöhl, H.; Vršnak, B.; Ruždjak, V.; Clette,
   F.; Hochedez, J. -F.; Roša, D.
2004A&A...414..707B    Altcode:
  Full-disc solar images obtained with the Extreme Ultraviolet Imaging
  Telescope (EIT) on board the Solar and Heliospheric Observatory
  (SOHO) are used to analyse solar differential rotation by tracing
  coronal bright points for the period June 4, 1998 to May 22, 1999. A
  method for the simultaneous determination of the true solar synodic
  rotation velocity and the height of the tracers is applied to data
  sets analysed with interactive and automatic methods. The calculated
  height of coronal bright points is on average 8000-12000 km above
  the photosphere. Corrected rotation velocities are transformed
  into sidereal ones and compared with results from the literature,
  obtained with various methods and tracers. The differential rotation
  profile determined by coronal bright points with the interactive method
  corresponds roughly to the profile obtained by correlating photospheric
  magnetic fields and the profile obtained from the automatic method
  corresponds roughly to the rotation of sunspot groups. This result is
  interpreted in terms of the differences obtained in the latitudinal
  distribution of coronal bright points using the two methods.

---------------------------------------------------------
Title: Exact solution of jump relations at discontinuities in a
    2.5-D reconnection model
Authors: Skender, M.; Vrsnak, B.; Martinis, M.
2004cosp...35..192S    Altcode: 2004cosp.meet..192S
  Exact solution of the complete set of jump relations at the rotational
  discontinuity and the slow mode shock in a two-and-half dimensional
  (2 1/2 - D) symmetric reconnection model is presented. The solution is
  used for analyzing the outflow jet characteristics in dependence on the
  speed and the incidence angle of the inflowing plasma, for a given shear
  of the inflow magnetic field. It is found that the outflow magnetosonic
  Mach number depends significantly on the incidence angle, the effect
  being more prominent at larger reconnection rates. Significant dynamical
  changes in the flow/field geometry are found in the transition to the
  2-D regime: In the region between the rotational discontinuity and the
  slow mode shock the direction of flow and the magnetic field become
  extremely sensitive to the degree of the magnetic field shear in the
  inflow. Implications for evolutionary systems like solar flares are
  discussed. M. Skender, B. Vrsnak, M.Martinis, Phys. Rev. E 68 (2003)
  046405

---------------------------------------------------------
Title: Forces governing coronal mass ejections
Authors: Vrsnak, B.
2004cosp...35..697V    Altcode: 2004cosp.meet..697V
  The general morphology and kinematics of coronal mass ejections (CMEs)
  are briefly described to outline physical aspects that are relevant for
  the understanding of CME propagation. The CME dynamics can be explained
  combining characteristics of the Lorentz force, the aerodynamic drag,
  and the gravity with the geometrical properties of CMEs. Whereas the
  Lorentz force plays a dominant role during the main acceleration
  stage that takes place within the distance of a few solar radii,
  the drag becomes essential in the upper corona and interplanetary
  space. Utilizing a large sample of more than 5000 CMEs measured
  in the distance range of 2--30 solar radii, the properties of the
  drag force are inspected. Analyzing the quadratic-form correlation,
  a =-k(v-v_0)| v-v_0|, between the acceleration, a, and the velocity,
  v, it is found that k is smaller for wider CMEs and decreases with
  heliocentric distance. Furthermore, v_0 increases with distance and
  is systematically larger than the slow solar wind speed by 100--200 km
  s<SUP>-1</SUP>. Such an excess of v_0 is explained assuming that in a
  certain fraction of events the propelling force is still acting in the
  considered distance range. In most events the inferred propelling-force
  acceleration at R=10 ranges between a_L=0 and 10 m s<SUP>-2</SUP>,
  being on average smaller at larger distances. However, there are also
  events showing a_L&gt;50 m s<SUP>-2</SUP>, as well as the events
  indicating a_L&lt;0. The prolonged acceleration of fast events is
  attributed to the reconnection below the erupting flux rope, which
  might also cause a two-ribbon flare if the associated energy release
  is powerful enough. Implications for the interplanetary motion of CMEs
  are discussed, emphasizing the prediction of the Sun-Earth transit time.

---------------------------------------------------------
Title: Are there really two types of cmes?
Authors: Vrsnak, B.
2004cosp...35..700V    Altcode: 2004cosp.meet..700V
  A statistical analysis of coronal mass ejections (CMEs) is performed
  to compare the kinematical properties of flare-associated (F)
  and non-flare (nF) CMEs. The study is based on measurements of
  545 F-CMEs and 211 nF-CMEs in the distance range R=2--30 solar
  radii. No statistically significant difference is found: e.g.,
  the mean accelerations and mean velocities amount to a_F=-1.8± 17 m
  s<SUP>-2</SUP>, a<SUB>nF</SUB>=-0.3± 19 m s<SUP>-2</SUP> and v_F=581±
  314 km s<SUP>-1</SUP>, v<SUB>nF</SUB>=576± 323 km s<SUP>-1</SUP>,
  respectively. Such an outcome indicates that the division of CMEs into
  two distinct categories is highly doubtful. The argument is strengthened
  by showing examples of fast F-CMEs significantly accelerating beyond
  R=2, and fast nF-CMEs moving at a constant speed or decelerating in the
  considered distance range. These examples disprove the scheme according
  to which the flare-associated CMEs are fast and move at a constant speed
  (or decelerate) in the coronagraph field of view, whereas the non-flare
  CMEs expose a gradual acceleration. Yet, it is shown that there is a
  well-defined relationship between the kinematical properties of CMEs
  and importance of associated flares: CMEs related to more powerful
  flares tend to be faster. However, the distribution of events along
  the speed-importance correlation is homogeneous, i.e., there is no
  grouping of CMEs into distinguishable classes. On the other hand, it
  is also found that wider CMEs are faster on average, and tend to show
  a prolonged acceleration phase. When only CMEs of a given width-class
  are isolated, the non-flare CMEs show kinematical parameters similar
  to CMEs associated with the flares of lowest importances. The results
  are interpreted in terms of the erupting flux rope model.

---------------------------------------------------------
Title: Magnetic reconnection in solar flares
Authors: Vršnak, B.; Skender, M.
2004HvaOB..28..103V    Altcode:
  Various aspects of solar flares are considered in the framework of
  analytic solutions of the complete set of MHD equations describing the
  2 1/2 -- D Petschek's reconnection model. In particular, we compare the
  theoretical results with characteristics of two-ribbon flares since they
  provide spatially resolved measurements of various plasma parameters. We
  emphasize the evolutionary aspect of the process, focusing on the
  effects of the change of the current sheet length-to-width ratio,
  longitudinal-to-transversal field ratio, and the ambient value of
  the plasma-to-magnetic pressure ratio. These parameters determine the
  conditions for the onset of fast reconnection, the transition to the
  turbulent reconnection regime, the spatial distribution of the density
  and temperature, and the efficiency of the particle acceleration.

---------------------------------------------------------
Title: Band-splitting of coronal and interplanetary type
    II bursts. III. Physical conditions in the upper corona and
    interplanetary space
Authors: Vršnak, B.; Magdalenić, J.; Zlobec, P.
2004A&A...413..753V    Altcode:
  We analyse properties of 58 type II radio bursts recorded in the
  meter-to-kilometer wavelength range, focusing on episodes of band-split
  emission. The basic two parameters utilized are the frequency drift
  D<SUB>f</SUB>=df/dt and the relative band-split BDW=Δ f/f of type
  II burst emission lanes. On average, in the meter-to-kilometer
  wavelength range D<SUB>f</SUB> increases with the emission frequency
  as D<SUB>f</SUB>∝ f<SUP>1.83</SUP>, revealing that source velocities
  are smaller at larger heliocentric distances. The relative band-split
  shows a weak but statistically significant dependence on the emission
  frequency, BDW∝ f<SUP>-0.06</SUP>, indicating an increase of BDW with
  the heliocentric distance. Combining the shock velocity estimated from
  the frequency drift, with the Mach number inferred from the band-split,
  the Alfvén speed and the magnetic field in the ambient plasma can
  be estimated as a function of the heliocentric distance r. However,
  the outcome directly depends on the coronal/interplanetary density
  model used, which is poorly known in the upper corona and the near-Sun
  interplanetary space. So, we invert the problem: utilizing the results
  of the previous paper where it was shown that beyond the heliocentric
  distance of two solar radii (r/r<SUB>⊙</SUB>=R&gt;2) the average
  magnetic field decreases approximately as B∝ R<SUP>-2</SUP>, we
  infer the density n(R) in the upper corona and near-Sun interplanetary
  space. The obtained empirical dependence n(R) is presented in the
  analytical form as a four-degree polynomial of 1/R, and is compared
  with some theoretical n(R) models, considering also a deviation from
  the B∝ 1/R<SUP>2</SUP> scaling used. The model matches the five-fold
  Saito density model (representing the active region corona) with the
  n∝ R<SUP>-2</SUP> regime in the interplanetary space. Furthermore, it
  is shown that on average the magnetosonic speed attains a local minimum
  of v<SUB>ms</SUB>≈ 400 km s<SUP>-1</SUP> around R=3 and a broad local
  maximum of v<SUB>ms</SUB>≈ 500 km s<SUP>-1</SUP> in the range R=4-6,
  beyond which it gradually decreases to several tens km s<SUP>-1</SUP>
  at 1 a.u. The local minimum becomes even deeper if the super-radial
  expansion of the magnetic field is taken into account. The implications
  regarding the formation and evolution of shocks in the corona and upper
  corona are discussed in the framework of CME-piston and flare-blast
  scenarios. The inferred general decrease of type II burst source
  velocities and broadening of band-splits with distance is interpreted
  in terms of the deceleration of mass ejections driving the shocks in
  the decreasing v<SUB>ms</SUB> environment. <P />Appendices A and B
  are only available in electronic form at http://www.edpsciences.org

---------------------------------------------------------
Title: Interaction of an Erupting Filament with the Ambient
    Magnetoplasma and Escape of Electron Beams
Authors: Vršnak, Bojan; Warmuth, Alexander; Maričić, Darije;
   Otruba, Wolfgang; Ruždjak, Vladimir
2003SoPh..217..187V    Altcode:
  A huge filament eruption of 12 September 2000 associated with a
  two-ribbon spotless flare is described. During the acceleration phase
  the shape of the filament changed, and signatures of topological
  restructuring of large-scale coronal magnetic fields were inferred
  by tracking changes of nearby coronal holes. At the same time
  electron beams associated with the flare impulsive phase escaped
  into interplanetary space. Based on the time-spatial relationships a
  hypothesis is put forward, according to which the reconnection between
  the arcade magnetic field and the ambient field provides a temporary
  link between the open field lines and the flare energy release site,
  enabling the escape of electron beams into interplanetary space.

---------------------------------------------------------
Title: Dynamics of coronal mass ejections in the near-Sun
    interplanetary space
Authors: Vrsnak, B.; Ruzdajak, D.; Sudar, D.; Gopalswamy, N.
2003ESASP.535..517V    Altcode: 2003iscs.symp..517V
  Kinematics of more than 5000 coronal mass ejections (CMEs) measured
  between 2 and 30 solar radii is investigated. A distinct relationship
  between the late-phase acceleration of CMEs and their velocities is
  found. It can be represented in the form a<SUB>[m s<SUP>-2</SUP>]</SUB>
  = -0.02(v-400)<SUB>[km s<SUP>-1</SUP>]</SUB>. The relationship is
  interpreted in terms of coupling of the CME motion and the solar wind,
  i.e., by the action of the aerodynamic drag. The results indicate that
  in the considered radial distance range the Lorentz force acceleration
  becomes weak, in the majority of the events spanning between 0 and 10
  m s<SUP>-2</SUP>. Implications for the interplanetary motion of CMEs
  are discussed, emphasising the prediction of the 1 a.u. arrival time.

---------------------------------------------------------
Title: Initiation and development of two coronal mass ejections
Authors: Maričić, D.; Vršnak, B.; Stanger, A. L.; Roša, D.;
   Hržina, D.
2003ESASP.535..441M    Altcode: 2003iscs.symp..441M
  We analyze the initiation and development of coronal mass ejections
  (CMEs) launched on 2001 May 15 and 2001 May 25. Both CMEs show clearly
  recognizable three-part structure already at low heights during
  the initial gradual rise in the pre-eruptive phase. This provides
  measurements of relative kinematics of the three-part structure from
  the very beginning of the eruption up to the post-acceleration phase. In
  both CMEs the frontal rim starts accelerating some 10-20 min before the
  prominence. However, the acceleration maximum of the prominence and the
  frontal rim was synchronized. CMEs attained the maximum acceleration
  of ≍350 m s<SUP>-2</SUP> and ≍250 m s<SUP>-2</SUP>, at the leading
  edge heliocentric distance R=2.4 and R=2.1 solar radii, respectively. In
  both cases the acceleration time profile of the frontal rim was broader
  than that of the prominence, although the peak values were similar. The
  CMEs attained velocities in excess of 1000 km s<SUP>-1</SUP>, showing
  a weak deceleration at large heights. The leading edge of CME starts
  decelerating before the prominence in both cases, indicating that the
  deceleration is caused by the aerodynamic drag force.

---------------------------------------------------------
Title: Radio signatures of fast oscillatory phenomena in the solar
    corona
Authors: Magdalenic, Jasmina; Zlobec, P.; Vršnak, B.; Messerotti,
   M.; Aurass, H.; Temmer, M.
2003ESASP.535..619M    Altcode: 2003iscs.symp..619M
  During type IV solar radio bursts different types of periodic fine
  structures (PFSs) are frequently observed, which can be interpreted
  as radio signatures of fast oscillatory phenomena in the coronal
  plasma. We analyze a large set of type IV bursts containing PFSs,
  recorded with high time resolution at single frequencies in the
  metric and decimetric bands. Focusing on the association with flares
  and flare-like phenomena we found: PFSs can be found in about 50% of
  type IV bursts characterized by fine structures; 10% of PFS-containing
  events are weak/short type IV-like radio bursts that occur in absence
  of any flare-like activity. In the weakest events the whole radio
  burst was in fact just one short PFS-episode recorded at only one
  observing frequency; In flare associated events we found two distinct
  classes of PFSs - impulsive phase and decay phase related PFSs; yet,
  no statistically significant difference in the characteristic periods
  and amplitudes is found between the two classes; PFS-rich radio events
  are characterized by large SXR and radio peak fluxes - neither one
  of the weak type IV bursts was PFS-rich. The opposite is not true:
  mainly powerful bursts are PFS-poor.

---------------------------------------------------------
Title: Properties of the solar velocity field indicated by motions
    of coronal bright points
Authors: Vršnak, B.; Brajša, R.; Wöhl, H.; Ruždjak, V.; Clette,
   F.; Hochedez, J. -F.
2003A&A...404.1117V    Altcode:
  Full-disc solar images obtained with the Extreme Ultraviolet Imaging
  Telescope (EIT) on board the Solar and Heliospheric Observatory (SOHO)
  are used to analyse properties of the solar velocity field by tracing
  coronal bright points from June 4, 1998 to May 22, 1999. Rotation
  velocity residuals, meridional motions and their relationship are
  investigated. Zones of slow and fast rotation found in motions of
  coronal bright points are consistent with the pattern of torsional
  oscillations, indicating that the statistical velocity pattern
  of bright point motions reflects the large-scale plasma flows. A
  complex pattern of meridional motion is deduced: The equatorward
  flows are found to dominate at low (B&lt;10<SUP>deg</SUP>) and high
  (B&gt;40<SUP>deg</SUP>) latitudes, whereas at mid-latitudes (B~
  10<SUP>deg</SUP>-40<SUP>deg</SUP>) a poleward flow is inferred. The
  complete data set shows no significant correlation between rotation
  residuals and meridional motions. However, when a subsample of
  coronal bright points including only the “point-like structures”
  (predominantly young bright points) is considered, a statistically
  significant correlation is found. On average, faster tracers show
  equatorward motion and the slower ones show poleward motion. Such
  a segregation is reflected in a statistically significant
  covariance of the rotation residuals and meridional velocities
  in the order of -1000 m<SUP>2</SUP> s<SUP>-2</SUP>, revealing an
  equatorward transport of angular momentum. The negative value of the
  covariance is provided by the high velocity tail in the velocity
  distribution of point-like structures, representing less than 15%
  of the population. The latitude dependence of the covariance can be
  expressed as Q=-62 B + 200 m<SUP>2</SUP> s<SUP>-2</SUP> covering the
  range B=0<SUP>deg</SUP>-60<SUP>deg</SUP>.

---------------------------------------------------------
Title: Solar rotation velocity determined by coronal bright points
Authors: Brajša, R.; Wöhl, H.; Vršnak, B.; Ruždjak, V.; Clette,
   F.; Hochedez, J. F.; Roša, D.; Hržina, D.
2003HvaOB..27...13B    Altcode:
  Full-disc solar images in the extreme ultraviolet part of the spectrum
  from the SOHO spacecraft (instrument EIT, data in the spectral line of
  Fe XV at a wavelength of 28.4 nm) are used to identify and trace coronal
  bright points with the interactive and automatic method. The Solar
  rotation was determined for the period June 4, 1998 to May 22, 1999
  and a two-step velocity filter was applied. Histograms of latitudinal
  and central meridian distance distributions of coronal bright points,
  for both solar hemispheres treated together (north and south, east and
  west), are presented and compared for different reduction procedures.

---------------------------------------------------------
Title: Analysis of periodical fine structures in type IV solar
    radio bursts
Authors: Magdaleníc, J.; Zlobec, P.; Vršnak, B.; Messerotti, M.;
   Auras, H.; Veronig, A.
2003HvaOB..27..131M    Altcode:
  Superimposed on the continuum of type IV solar radio bursts
  fine structures are often observed. We analysed a large data set
  of periodical fine structures recorded with high time resolution
  at single frequencies (metric to decimetric bands) by the Trieste
  Solar Radio System. Diverse classes of fine structures with similar
  periodical behaviour but different time profiles and polarization
  characteristics were identified. It is demonstrated that on the average
  pulsation periods decrease with increasing observing frequency, and
  that pulsations recorded above ≈ 600 MHz could be of different nature
  than pulsations below ≈ 400 MHz.

---------------------------------------------------------
Title: Flare waves revisited
Authors: Warmuth, A.; Vršnak, B.; Hanslmeier, A.
2003HvaOB..27..139W    Altcode:
  Recently, the flare wave phenomenon has come back into focus prompted
  by the observation of coronal waves with the SOHO/EIT instrument
  (EIT waves). It has been suggested that they represent the coronal
  counterpart to the chromospheric Moreton waves, but this interpretation
  has remained a matter of debate. In order to make inferences on the
  physical nature of the phenomenon, 12 flare wave events are studied
  using Hα, EUV, Helium I, SXR and radio data. The wavefronts in
  the various spectral ranges are following very similar kinematical
  curves, which suggests that they are caused by the same physical
  disturbance. The characteristics of this disturbance -- deceleration,
  perturbation profile broadening, and perturbation amplitude decrease
  -- can be interpreted in terms of a freely propagating fast-mode MHD
  shock which decays to an ordinary fast-mode wave. This scenario also
  accounts for the associated metric type II radio bursts.

---------------------------------------------------------
Title: Magnetic 3-D Configurations of Energy Release in Solar Flares
Authors: Vrsnak, B.
2003LNP...612...28V    Altcode: 2003ecpa.conf...28V
  Basic concepts and principles usually used to interpret the solar
  flare phenomenon are summarized, and traditional classification schemes
  based on 2-D magnetic field representations are briefly reviewed. The
  extension to 3-D opens new aspects, some of which are sketched in this
  paper: In particular two-loop interactions, two-ribbon flare geometry,
  and the plasmoid formation in a current sheet are considered. It
  is shown that alternative onset processes exist beside the standard
  two-ribbon flare scenario in which the pre-flare arcade evolves slowly
  through a series of equilibrium states until the eruption. For example,
  the arcade can become unstable after an abrupt reformation of its core
  through a sequence of loop interactions. The restructuration results in
  an impulsive compact flare and the formation of an unstable `sigmoid'
  whose eruption provides the two-ribbon phase aftermath. Possible
  modalities of main phase are emphasized. Especially the secondary
  plasmoid formation is considered and its fate discussed stressing
  the 3-D aspect of the process and the effect of line-tying. Finally,
  complex events composed of several distinct, but causally related
  energy release processes are described.

---------------------------------------------------------
Title: Solar type II radio bursts: emission from shock segments with
    a collapsing trap geometry?
Authors: Magdalenić, J.; Vršnak, B.; Aurass, H.
2002ESASP.506..335M    Altcode: 2002svco.conf..335M; 2002ESPM...10..335M
  The nature of the band-split type II burst radio emission is
  discussed. Examples are shown in which the extrapolations of band-split
  lanes of type II bursts recorded in the hekto-kilometric wavelength
  range fit to the local frequency jump caused by the passage of the
  associated interplanetary MHD shock wave at 1 AU. Such cases favour
  the interpretation of band-split in terms of the emission from the
  upstream and downstream shock region. On the other hand type II bursts
  sometimes show relative band-splits smaller than 10%, indicating that
  even low amplitude shocks can excite the type II burst emission. This
  implies that an additional mechanism is accelerating electrons at
  such shocks. It is proposed that the band-split type II emission is
  excited at quasi-perpendicular shock segments forming a collapsing trap
  geometry. In such a configuration a particular magnetic field line
  intersects the shock front twice forming a system of two approaching
  magnetic mirrors in which electrons can be accelerated.

---------------------------------------------------------
Title: Energy release from a large-scale magnetic null point in
    the corona?
Authors: Aurass, Henry; Hofmann, Axel; Vršnak, Bojan
2002ESASP.506..423A    Altcode: 2002svco.conf..423A; 2002ESPM...10..423A
  We observed how a flare disturbes a system of interconnecting loops
  between neighboring active regions. The disturbed loops brighten in
  SOHO/EIT images of the coronal magnetoplasma. They are part of a large
  scale structure embracing a weak field range in the photospheric and
  coronal magnetic field. Near the weak field site but away from active
  regions and from the EIT-detected loopl heating, an initially narrowband
  nonthermal meter wave radio source is observed by the AIP spectrometer
  and the Nançay radio heliograph. The formation of this source and the
  EIT loop brightening can be consequences of current sheet activation
  and excessive coronal heating at a disturbed magnetic null point.

---------------------------------------------------------
Title: Physical conditions in the reconnection outflow
Authors: Skender, M.; Vršnak, B.; Martinis, M.
2002ESASP.506..757S    Altcode: 2002svco.conf..757S; 2002ESPM...10..757S
  The amplitude of the standing fast mode shock formed in the reconnection
  outflow is studied. The dependence on the Mach number of the inflow,
  the direction of the inflow, the transversal magnetic field, and the
  plasma to magnetic pressure ratio is investigated in 2-D and 2 1/2-D
  model separately. The results are presented stressing the observable
  quantities such as the band-split of the radio emission excited in the
  upstream and downstream regions of the fast mode shock. For the range
  of parameter values appropriate for the occurrence of solar flares it
  is found that the relative band-split should be in the range 10-50%.

---------------------------------------------------------
Title: Coronal and interplanetary magnetic fields inferred from
    band-splitting of type II bursts
Authors: Vršnak, B.; Magdalenić, J.; Aurass, H.; Mann, G.
2002ESASP.506..409V    Altcode: 2002svco.conf..409V; 2002ESPM...10..409V
  Adopting that the band-splitting of type II bursts is a consequence
  of the plasma emission from the upstream and downstream shock region,
  the band-split reveals the shock Mach number. On the other hand,
  the shock speed can be inferred from the frequency drift. Combining
  these two parameters the Alfvén velocity and the magnetic field in
  the ambient plasma can be estimated. The results of such an analysis
  applied to 44 type II bursts recorded from decimetric to kilometric
  wavelengths are presented. The inferred magnetic field decreases as
  R<SUP>-2</SUP> beyond the radial distance of 1.5 solar radii (R &gt;
  1.5) if the two-fold Saito density model is applied at R &lt; 10 and
  Leblanc model beyond R ≍ 30. In that case the Alfvén velocity shows
  a shallow local minimum of v<SUB>A</SUB> ≍ 400 km s<SUP>-1</SUP>
  at 2 &lt; R &lt; 3 and a broad local maximum of v<SUB>A</SUB> ≍ 500
  km s<SUP>-1</SUP> at 4 &lt; R &lt; 6.

---------------------------------------------------------
Title: Band-splitting of coronal and interplanetary type II
    bursts. II. Coronal magnetic field and Alfvén velocity
Authors: Vršnak, B.; Magdalenić, J.; Aurass, H.; Mann, G.
2002A&A...396..673V    Altcode:
  Type II radio bursts recorded in the metric wavelength range are
  excited by MHD shocks traveling through the solar corona. They often
  expose the fundamental and harmonic emission band, both frequently
  being split in two parallel lanes that show a similar frequency drift
  and intensity behaviour. Our previous paper showed that band-splitting
  of such characteristics is a consequence of the plasma emission from
  the upstream and downstream shock regions. Consequently, the split
  can be used to evaluate the density jump at the shock front and to
  estimate the shock Mach number, which in combination with the shock
  speed inferred from the frequency drift provides an estimate of the
  Alfvén velocity and the magnetic field in the ambient plasma. In this
  paper such a procedure is applied to 18 metric type II bursts with the
  fundamental band starting frequencies up to 270 MHz. The obtained values
  show a minimum of the Alfvén velocity at the heliocentric distance R~ 2
  amounting to v<SUB>A</SUB>~ 400-500 km s<SUP>-1</SUP>. It then increases
  achieving a local maximum of v<SUB>A</SUB>~ 450-700 km s<SUP>-1</SUP>
  at R~ 2.5. The implications regarding the process of formation and decay
  of MHD shocks in the corona are discussed. The coronal magnetic field in
  the range 1.3&lt;R&lt;3 decreases as R<SUP>-3</SUP> to R<SUP>-4</SUP>,
  or H<SUP>-1.5</SUP> to H <SUP>-2</SUP> if expressed as a function
  of the height. The results are compared with other estimates of the
  coronal magnetic field in the range 1&lt;R&lt;10. Combined data show
  that below H&lt;0.3 the magnetic field is dominated by active region
  fields, whereas above H=1 it becomes radial, behaving roughly as B=2x
  R<SUP>-2</SUP> with a plausible value of B~ 5 nT at 1 a.u.

---------------------------------------------------------
Title: The Neupert effect and the electron-beam-driven evaporation
    model
Authors: Veronig, A.; Vršnak, B.; Dennis, B. R.; Temmer, M.;
   Hanslmeier, A.; Magdalenić, J.
2002ESASP.506..367V    Altcode: 2002svco.conf..367V; 2002ESPM...10..367V
  Based on a sample of ~1100 solar flares observed simultaneously in
  hard and soft X-rays, we performed a statistical analysis of the
  Neupert effect. For a subset of ~500 events, supplementary Hα flare
  data were considered. The timing behavior of &gt;50% of the events
  is consistent with the Neupert effect. A high correlation between
  the soft X-ray peak flux and the hard X-ray fluence is obtained,
  being indicative of electron-beam-driven evaporation. However, about
  one fourth of the events (predominantly weak flares) reveal strong
  deviations from the predicted timing, with a prolonged increase of
  the thermal emission beyond the end of the hard X-rays. These findings
  suggest that electron-beam-driven evaporation plays an important role
  in solar flares. Yet, in a significant fraction of events there is also
  evidence for an additional energy transport mechanism from the energy
  release site other than electron beams, presumably thermal conduction.

---------------------------------------------------------
Title: Morphology and polarization of metric and decimetric solar
radio pulsations: a statistical approach
Authors: Magdalenić, J.; Zlobec, P.; Messerotti, M.; Vršnak, B.
2002ESASP.506..331M    Altcode: 2002ESPM...10..331M; 2002svco.conf..331M
  We analyzed a large data set of fine structures observed during type
  IV solar radio events recorded with high time resolution at single
  frequencies in the metric and decimetric bands by the Trieste Solar
  Radio System. Varieties of fine structures with periodical behavior
  but different temporal morphologies and polarization characteristics
  were identified. For selected events general statistics was derived
  in order to describe the evolution in time and at different observing
  frequencies, i.e. to infer the evolution of the related coronal plasma
  disturbances in time and height. To better characterize the observed
  radio pulsations in the framework of the flaring process, we derived
  the positions of the associated active regions, and studied the timing
  of such radio phenomena with respect to the associated SXR flares.

---------------------------------------------------------
Title: The Neupert effect in solar flares and implications for
    coronal heating
Authors: Veronig, A.; Vrsnak, B.; Dennis, B. R.; Temmer, M.;
   Hanslmeier, A.; Magdalenić, J.
2002ESASP.505..599V    Altcode: 2002solm.conf..599V; 2002IAUCo.188..599V; 2002astro.ph..8089V
  Based on simultaneous observations of solar flares in hard and soft
  X-rays we studied several aspects of the Neupert effect. About half of
  1114 analyzed events show a timing behavior consistent with the Neupert
  effect. For these events, a high correlation between the soft X-ray
  peak flux and the hard X-ray fluence is obtained, being indicative of
  electron-beam-driven evaporation. However, for about one fourth of the
  events there is strong evidence for an additional heating agent other
  than electron beams. We discuss the relevance of these findings with
  respect to Parker's idea of coronal heating by nanoflares.

---------------------------------------------------------
Title: Flare waves observed in Helium I 10 830 Å. A link between
    Hα Moreton and EIT waves
Authors: Vršnak, B.; Warmuth, A.; Brajša, R.; Hanslmeier, A.
2002A&A...394..299V    Altcode:
  Three traveling disturbances recorded in the absorption line of
  Helium I at 10 830 Å, (He I), analogous to Hα Moreton waves,
  are analyzed. The morphology and kinematics of the wavefronts are
  described in detail. The He I wave appears as an expanding arc of
  increased absorption roughly corresponding to the Hα disturbance,
  although not as sharply defined. He I perturbations consist of a
  relatively uniform diffuse component and a patchy one that appears as
  enhanced absorption in He I mottles. It leads the Hα front by some
  20 Mm and can be followed to considerably larger distances than in
  Hα observations. Behind the front stationary areas of reduced He I
  absorption develop, resembling EUV coronal dimming. The observed He I
  as well as the Hα disturbances show a deceleration of the order of
  100-1000 m s<SUP>-2</SUP>. Moreover, in the event where Hα , He I,
  and EUV wavefronts are observed, all of them follow closely related
  kinematical curves, indicating that they are a consequence of a common
  disturbance. The analysis of spatial perturbation profiles indicates
  that He I disturbances consist of a forerunner and a main dip, the
  latter being cospatial with the Hα disturbance. The properties and
  behavior of the wavefronts can be comprehended as a consequence of a
  fast-mode MHD coronal shock whose front is weakly inclined to the solar
  surface. The Hα disturbance and the main He I dip are a consequence
  of the pressure jump in the corona behind the shock front. The He I
  forerunner might be caused by thermal conduction from the oblique shock
  segments ahead of the shock-chromosphere intersection, or by electron
  beams accelerated in the quasi-perpendicular section of the shock.

---------------------------------------------------------
Title: Investigation of the Neupert effect in solar
    flares. I. Statistical properties and the evaporation model
Authors: Veronig, A.; Vršnak, B.; Dennis, B. R.; Temmer, M.;
   Hanslmeier, A.; Magdalenić, J.
2002A&A...392..699V    Altcode: 2002astro.ph..7217V
  Based on a sample of 1114 flares observed simultaneously in hard X-rays
  (HXR) by the BATSE instrument and in soft X-rays (SXR) by GOES, we
  studied several aspects of the Neupert effect and its interpretation
  in the frame of the electron-beam-driven evaporation model. In
  particular, we investigated the time differences (Delta t) between
  the maximum of the SXR emission and the end of the HXR emission,
  which are expected to occur at almost the same time. Furthermore,
  we performed a detailed analysis of the SXR peak flux - HXR fluence
  relationship for the complete set of events, as well as separately for
  subsets of events which are likely compatible/incompatible with the
  timing expectations of the Neupert effect. The distribution of the time
  differences reveals a pronounced peak at Delta t = 0. About half of the
  events show a timing behavior which can be considered to be consistent
  with the expectations from the Neupert effect. For these events, a high
  correlation between the SXR peak flux and the HXR fluence is obtained,
  indicative of electron-beam-driven evaporation. However, there is also
  a significant fraction of flares (about one fourth), which show strong
  deviations from Delta t = 0, with a prolonged increase of the SXR
  emission distinctly beyond the end of the HXR emission. These results
  suggest that electron-beam-driven evaporation plays an important role
  in solar flares. Yet, in a significant fraction of events, there is
  also clear evidence for the presence of an additional energy transport
  mechanism other than nonthermal electron beams, where the relative
  contribution is found to vary with the flare importance.

---------------------------------------------------------
Title: Solar differential rotation determined by tracing coronal
    bright points in SOHO-EIT images. II. Results for 1998/99 obtained
    with interactive and automatic methods
Authors: Brajša, R.; Wöhl, H.; Vršnak, B.; Ruždjak, V.; Clette,
   F.; Hochedez, J. -F.
2002A&A...392..329B    Altcode:
  Full-disc solar images obtained with the Extreme Ultraviolet Imaging
  Telescope (EIT) on board the Solar and Heliospheric Observatory (SOHO)
  were used to analyse solar differential rotation by tracing coronal
  bright points. The results obtained with the interactive and the
  automatic method for the time period June 4, 1998 to May 22, 1999 are
  presented and compared. A possible north-south rotational asymmetry
  and differences in the rotation velocity curves for various subtypes
  of tracers are investigated.

---------------------------------------------------------
Title: Relative timing of solar flares observed at different
    wavelengths
Authors: Veronig, A.; Vršnak, B.; Temmer, M.; Hanslmeier, A.
2002SoPh..208..297V    Altcode: 2002astro.ph..8088V
  The timing of 503 solar flares observed simultaneously in hard X-rays,
  soft X-rays and Hα is analyzed. We investigated the start and the peak
  time differences in different wavelengths, as well as the differences
  between the end of the hard X-ray emission and the maximum of the
  soft X-ray and Hα emission. In more than 90% of the analyzed events,
  a thermal pre-heating seen in soft X-rays is present prior to the
  impulsive flare phase. On average, the soft X-ray emission starts 3 min
  before the hard X-ray and the Hα emission. No correlation between the
  duration of the pre-heating phase and the importance of the subsequent
  flare is found. Furthermore, the duration of the pre-heating phase
  does not differ for impulsive and gradual flares. For at least half of
  the events, the end of the non-thermal emission coincides well with
  the maximum of the thermal emission, consistent with the beam-driven
  evaporation model. On the other hand, for ∼ 25% of the events there
  is strong evidence for prolonged evaporation beyond the end of the
  hard X-rays. For these events, the presence of an additional energy
  transport mechanism, most probably thermal conduction, seems to play
  an important role.

---------------------------------------------------------
Title: Differential Rotation of Stable Recurrent Sunspot Groups
Authors: Brajša, R.; Wöhl, H.; Vršnak, B.; Ruždjak, D.; Sudar,
   D.; Roša, D.; Hržina, D.
2002SoPh..206..229B    Altcode:
  Stable recurrent sunspot groups from the Greenwich data set which
  were identified in at least two subsequent solar rotations were
  traced. The solar rotation was determined by the period method from
  the time difference of the two central meridian passages of each of
  the 327 identified groups. Sidereal rotation periods were calculated
  from the synodic ones by a seasonal-dependent procedure taking into
  account the details of the Earth's motion around the Sun. Growing
  recurrent sunspot groups rotate on the average faster than decaying
  recurrent sunspot groups, while sunspot groups of all types taken
  together rotate faster than both growing and decaying recurrent sunspot
  groups. A north-south rotational asymmetry and a cycle-dependence of
  rotational velocity of recurrent sunspot groups were analyzed. Positive
  rotation velocity deviations are larger, but less numerous than the
  negative ones. Signatures of torsional oscillations were not found
  analyzing the rotation velocity residual of recurrent sunspot groups
  as a function of the distance from the average latitude of activity.

---------------------------------------------------------
Title: Shock-excited radio burst from reconnection outflow jet?
Authors: Aurass, H.; Vršnak, B.; Mann, G.
2002A&A...384..273A    Altcode:
  Models of dynamic (two-ribbon-, arcade) flares involve the formation
  of a system of standing slow and possibly also fast mode shock waves
  associated with the fast reconnection process below the erupting
  filament. These shocks are anticipated theoretically, but are not
  unambiguously confirmed by observations. In this paper we identify for
  the first time the radio signature of a fast mode outflow termination
  shock in a dynamic radio burst spectrogram. The standing fast mode
  shock is revealed by a zero-drift type II burst recorded between 300
  and 400 MHz. It started almost 1 hour after the impulsive phase of
  the 7 April 1997 flare and lasted for more than 30 min. The burst
  shows a characteristic herringbone fine structure and a band split
  of (10+/-6)% of the emission frequency. No fundamental-harmonic
  pattern was observed, and we argue that the feature is fundamental
  mode emission. Simultaneous imaging observations (Hα , Yohkoh SXT,
  SOHO EIT) show a relaxed postflare loop arcade with a bright soft X-ray
  cusp commonly interpreted as a typical reconnection pattern. Conditions
  for termination shock formation and excitation of radio emision are
  investigated. Favourable circumstances for the radio detection of a
  termination shock in the reconnection outflow are a comparatively large
  height of the diffusion region, a low plasma to magnetic pressure
  ratio beta upstream of the slow shocks, and a small angle between
  the reconnecting field lines. Finally, we discuss why similar radio
  signatures are not observed more frequently, and why it appeared
  so late in the event. We stress the implications and point to some
  inconsistencies which might be a consequence of commonly practiced ad
  hoc application of idealized model results to realistic conditions.

---------------------------------------------------------
Title: Moreton waves and their relation with EIT waves
Authors: Warmuth, Alexander; Vršnak, Bojan; Aurass, Henry; Hanslmeier,
   Arnold
2002ESASP.477..195W    Altcode: 2002scsw.conf..195W
  Moreton waves, observed in Hα, and the recently discovered coronal
  transients known as "EIT waves" have remained fairly poorly understood
  phenomena. In particular, the issues of their mutual association and of
  the nature of their driver are not resolved. We discuss seven Moreton
  waves observed in Hα and derive their basic characteristics. Four of
  these events were observed simultaneously in Hα and EUV. A deceleration
  of the disturbances is found in all cases. In the 2 May 1998 event,
  the cospatiality of Moreton and EIT wave fronts is established and
  a detailed analysis of the evolution of the Hα wave, its kinematics
  and perturbation profile is carried out. The results - deceleration,
  broadening, and decrease of intensity of the profiles - favor the
  fast-mode shock ("blast wave") scenario over the CME-associated magnetic
  field evolution hypothesis.

---------------------------------------------------------
Title: Influence of the aerodynamic drag on the motion of
    interplanetary ejecta
Authors: Vršnak, Bojan; Gopalswamy, Nat
2002JGRA..107.1019V    Altcode:
  A simple semi-empirical model for the motion of interplanetary ejecta is
  proposed to advance the prediction of their arrival times at Earth. It
  is considered that the driving force and the gravity are much smaller
  than the aerodynamic drag force. The interaction with the ambient solar
  wind is modeled using a simple expression for the acceleration $[\dot
  \upsilon \]$ = -γ(υ-w), where w = w(R) is the distance-dependent
  solar wind speed. It is assumed that the coefficient γ decreases
  with the heliocentric distance as γ = αR<SUP>-β</SUP>, where α
  and β are constants. The equation of motion is integrated numerically
  to relate the Earth transit time and the associated in situ velocity
  with the velocity of coronal mass ejection. The results reproduce well
  the observations in the whole velocity range of interest. The model
  values are compared with some other models in which the interplanetary
  acceleration is not velocity dependent, as well as with the model where
  the drag acceleration is quadratic in velocity $\[\dot \upsilon \]$
  = -γ<SUB>2</SUB>(υ - w)|υ - w|.

---------------------------------------------------------
Title: Radio Shocks from Reconnection Outflow Jet? - New Observations
Authors: Aurass, H.; Karlicky, M.; Thompson, B. J.; Vršnak, B.
2002mwoc.conf..401A    Altcode:
  The common analysis of dynamic radio spectrograms with Yohkoh X-ray
  images yields information about possible associations between
  nonthermal electron acceleration and changes in hot and dense
  plasma-magnetic field structures of the corona. Examples are correlated
  X-ray-jet--electron beam injections (type III/U bursts), motions of
  X-ray blobs and correlated shock-driven (type II) radio bursts, and
  sigmoid evolution associated with characteristic type IV burst spectral
  fine structures. Here, we demonstrate the first identification of the
  radio signature of a reconnection outflow termination shock during a
  dynamic flare. Reconnection of magnetic fields is one flare energy
  release mechanism. During dynamic flares there is formed a system
  of standing slow and - sometimes - also fast mode shock waves in the
  space around the diffusion region. This standing fast mode shock is
  revealed by a zero-drift type II burst between 300 and 400 MHz. It
  exists more than 30 min starting 1 hour after the impulsive flare on
  07 April 1997 in AR 8027. It shows herringbone fine structure and 10%
  band splitted lanes. We argue for having detected fundamental mode
  emission. No fundamental-harmonic pattern was observed. Simultaneous
  imaging observations (Hα, Yohkoh SXT, SOHO EIT) show a postflare loop
  arcade with a bright soft X-ray cusp. Preferable conditions for the
  radio detection of the termination shock are a low plasma to magnetic
  pressure ratio eta upstream of the slow shocks, a low diffusion region
  rise velocity, and a low reconnection rate. The occurrence of the
  termination shock is most probable in late stage of flares.

---------------------------------------------------------
Title: Processes Governing Coronal and Interplanetary Ejecta
Authors: Vrsnak, B.
2001AGUFMSH12A0741V    Altcode:
  Basic features of coronal mass ejections (CMEs) are surveyed, relating
  the observations in chromospheric and transition region spectral lines
  with white light coronographic observations. The pre-eruptive prominence
  evolution, including the development of internal (helical) structure
  is emphasized. Various processes causing destabilization of the
  arcade/filament system are noted. Properties of the acceleration phase,
  including the relationship between the dynamics of prominence, cavity,
  and leading edge of CMEs are stressed revealing various acceleration
  scenarios. The decrease of the helical fine structure pitch angle
  and the mass leakage estimated in some prominences are presented as
  a function of time and compared with acceleration curves. The events
  showing a deceleration in late phases of cronographic observations
  are used to estimate the influence of the drag force on the flux rope
  motion and to evaluate the propelling Lorentz force. The CME velocities,
  earth transit times, and in situ measured velocities are analyzed to
  infer the intreplanetary dynamics of ejecta.\The observational features
  described are explained considering the Lorentz force acting in the
  line-tied semi-toroidal flux rope, the gravity, and the aerodynamic
  drag. At low heights (initial stage) dominant forces are the Lorentz
  force and gravity. After the ejection attains velocity in the order of
  100 km s<SUP>-1</SUP> the influence of the aerodynamic drag becomes
  important. Since the cold and dense prominence material is leaking
  down the rope's legs, and the height increases, the gravity soon
  becomes negligible. The Lorentz force also starts decreasing beyond
  radial distances of several solar radii. Its action might be enhanced
  and prolonged by effects of the reconnection below the rope (long
  duration flare association) and by the redistribution of twist into
  the expanded uppermost parts of the rope. At large distances the drag
  becomes the dominant force. Fast ejecta start decelerating, whereas
  those in which the Lorentz force was too weak and the ejection did not
  surpass the solar wind speed get an additional acceleration: In the
  interplanetary space ejecta asymptotically approach the wind velocity.

---------------------------------------------------------
Title: Dynamics of solar coronal eruptions
Authors: Vršnak, Bojan
2001JGR...10625249V    Altcode:
  The kinematics of 87 solar eruptive events (flare sprays, eruptive
  prominences, and coronal transients) observed above the solar limb
  are studied. The data reveal a clear statistical trend for the
  highest measured value of the acceleration to be lower in the events
  taking place at a larger radial distance. The majority of events
  (84%) show a phase of exponential-like growth of the velocity. The
  growth rate decreases with the height at which this regime sets in. A
  phase of constant acceleration was found only in 11% of cases. In the
  postacceleration phase a constant velocity regime was found in 57% of
  events. A considerable number of eruptions (32%) exposed a deceleration,
  most often showing an exponential-like decay of the velocity. The
  related theoretical models are confronted with the observations,
  and the implications are discussed.

---------------------------------------------------------
Title: Solar flares and coronal shock waves
Authors: Vršnak, Bojan
2001JGR...10625291V    Altcode:
  The ignition of coronal shock waves by solar flares is
  investigated confronting the results of a simple MHD model with the
  observations. Characteristics of type II bursts recorded in the metric
  and decametric wavelength range are compared with the properties of
  the microwave and soft X-ray bursts of the associated flares. The time
  delay of the type II burst beginning after the onset of a flare is
  found to be shorter for shorter rise time of a flare burst and for
  a more powerful flare. Starting frequencies of type II bursts are
  higher for more impulsive flares. Instantaneous relative bandwidths
  of the type II bursts are larger for more powerful flares, indicating
  a higher Mach number of the shock. Consistent with this, a positive
  correlation between the flare importance and the inferred shock velocity
  is found. The results are fully consistent with the implications of
  the model describing the shock formation by a flare-ignited blast wave.

---------------------------------------------------------
Title: Evolution of Two EIT/Hα Moreton Waves
Authors: Warmuth, A.; Vršnak, B.; Aurass, H.; Hanslmeier, A.
2001ApJ...560L.105W    Altcode:
  Since the discovery of EIT waves, questions have remained about
  the driver of these disturbances and their association with the
  chromospheric Moreton waves. In order to resolve some of these issues,
  two flare-associated transient events (1997 November 3 and 1998 May 2)
  observed simultaneously in Hα and EIT are analyzed. The cospatiality
  of Moreton and EIT wave fronts is established, and a deceleration of
  the disturbances is found in both events. In the case of 1998 May 2, a
  detailed analysis of the evolution of the Moreton wave, its kinematics,
  and perturbation profile is carried out. The results-deceleration,
  broadening, and decrease of intensity of the profiles-favor the
  fast-mode shock (“blast wave”) scenario over the coronal mass
  ejection-associated magnetic field evolution hypothesis.

---------------------------------------------------------
Title: Band-splitting of coronal and interplanetary type II
    bursts. I. Basic properties
Authors: Vršnak, B.; Aurass, H.; Magdalenić, J.; Gopalswamy, N.
2001A&A...377..321V    Altcode:
  Patterns analogous to the band-splitting of metric type II bursts are
  found in a number of type II bursts observed in the dekameter-kilometer
  wavelength range. A similarity of morphological and frequency-time
  characteristics of two emission components are indicative of a
  common source. Relative frequency splits span in the range Delta
  f/f=0.05-0.6. At radial distances between 2 and 4 R<SUB>sun</SUB> only
  small splits around 0.1 can be found. In the interplanetary space the
  relative split on average increases with the radial distance, whereas
  the inferred shock velocity decreases. In three events extrapolations
  of the split components point to the base and the peak of the jump
  in the local plasma frequency caused by the associated shock passage
  at 1 AU. This is suggestive of the plasma radiation from the regions
  upstream and downstream of the shock. Adopting this interpretation, one
  finds that the drop of Delta f/f at 2-4 R<SUB>sun</SUB> is congruent
  with the Alfvén velocity maximum expected there. The split increase
  and the velocity decrease at larger distances can be explained as a
  consequence of declining Alfvén speed in the interplanetary space.

---------------------------------------------------------
Title: Comparative Analysis of Type ii Bursts and of Thermal and
    non-Thermal Flare Signatures
Authors: Vršnak, B.; Magdalenić, J.; Aurass, H.
2001SoPh..202..319V    Altcode:
  The relationship between metric type II radio bursts and solar flares is
  studied. Well-defined correlations between the properties of type II
  bursts and the characteristics of associated microwave and soft X-ray
  bursts are established in two entirely independent data sets. It is
  shown that the correlations are strongly affected by the wide range
  of coronal Alfvén velocities involved, comprising values from only
  150 up to 800 km s<SUP>−1</SUP>, with a typical value of 400 km
  s<SUP>−1</SUP>. After careful data analysis it was inferred that
  type II bursts are more closely related to the soft X-ray bursts than
  they are to microwave bursts. The correlations indicate that type II
  burst shocks are preferably generated by flares with a relatively
  strong thermal component, and that the shocks are probably ignited
  by the plasma expansion associated with the 'evaporation' process in
  the transition region. Although the results imply that the majority
  of metric type II bursts are caused by flares, a simple geometrical
  consideration shows that a fraction of non-flare type II bursts cannot
  be explained by behind-limb events and that roughly 10% of metric type
  II bursts should be attributed to non-flare coronal mass ejections.

---------------------------------------------------------
Title: Deceleration of Coronal Mass Ejections
Authors: Vršnak, Bojan
2001SoPh..202..173V    Altcode:
  Decelerated motion of 12 coronal eruptions is studied. It is found that
  the measured decelerations and deceleration rates depend on the events'
  plane-of-sky velocities and heights. The dependence of deceleration on
  the velocity is described better by a quadratic function then by linear
  fit. Results are interpreted in terms of a viscous drag. An empirical
  relation expressing the decrease of the drag effectiveness with the
  projected height is established. The interplay between the Lorentz
  force, viscous drag, and gravity is discussed. Several examples are
  considered to illustrate the relative contributions of these forces
  under various circumstances.

---------------------------------------------------------
Title: Solar differential rotation determined by tracing coronal
    bright points in SOHO-EIT images. I. Interactive and automatic
    methods of data reduction
Authors: Brajša, R.; Wöhl, H.; Vršnak, B.; Ruždjak, V.; Clette,
   F.; Hochedez, J. -F.
2001A&A...374..309B    Altcode:
  Full-disc solar images obtained with the Extreme Ultraviolet Imaging
  Telescope (EIT) on board the Solar and Heliospheric Observatory (SOHO)
  were used to analyse solar differential rotation determined by tracing
  coronal bright points. Two different procedures were developed and
  compared: an interactive and an automatic method. The interactive method
  is based on the visual tracing of coronal bright points in consecutive
  images using computer programs written in the Interactive Data Language
  (IDL). The automatic method relies on the IDL procedure “Regions Of
  Interest (ROI) segmentation” which is used to detect and follow bright
  points in triplets of consecutive images. The test-results obtained
  applying both methods by different persons who performed tracing are
  presented and compared. The advantages and disadvantages of the two
  methods are discussed.

---------------------------------------------------------
Title: On the Rigid Component in the Solar Rotation
Authors: Brajša, R.; Ruždjak, V.; Vršnak, B.; Wöhl, H.;
   Pohjolainen, S.; Urpo, S.
2001ASSL..259..263B    Altcode: 2001dysu.conf..263B
  A rigid component in the rotation velocity determined by tracing low
  brightness temperature regions in the microwave regime was found and
  interpreted in terms of their association rate (39%) with rigidly
  rotating “pivot-points".

---------------------------------------------------------
Title: Onset of Metric and Kilometric Type II Bursts
Authors: Vršnak, B.
2001ASSL..259..255V    Altcode: 2001dysu.conf..255V
  A model governing the evolution of a large amplitude magnetosonic
  wave is applied to coronal and interplanetary conditions, with the
  aim to investigate the starting frequencies and the onset times of
  metric and kilometric type II bursts. The results are compared with
  the statistical properties of a sample of metric type II bursts and
  the associated flares.

---------------------------------------------------------
Title: Formation of Coronal Shock Waves
Authors: Vršnak, B.
2001ASSL..259..251V    Altcode: 2001dysu.conf..251V
  The evolution of the leading edge of a large amplitude perturbation
  is studied to investigate the formation of a perpendicular MHD shock
  wave. The results are applicable to metric and kilometric solar
  type~II bursts.

---------------------------------------------------------
Title: An Analysis of the Solar Rotation Velocity by Tracing Coronal
    Features
Authors: Brajsa, R.; Vrsnak, B.; Ruzdjak, V.; Rosa, D.; Hrzina, D.;
   Wöhl, H.; Clette, F.; Hochedez, J. -F.
2001IAUS..203..377B    Altcode:
  Full-disc solar images in the extreme ultraviolet part of the spectrum
  from the SOHO spacecraft (EIT) are used to identify various coronal
  structures appropriate for the solar rotation determination (e.g. bright
  points and coronal holes). From the time differences in tracer positions
  (more than 1 image per day) solar rotation velocities are measured,
  primarily by well-defined tracers, such as coronal bright points, whose
  large number and broad coverage of latitudes may provide an unique
  opportunity for a solar rotation analysis. The analysis started using
  the SOHO data from 1997-1999 and preliminary experiences obtained
  measuring solar rotation from the full-disc images in soft X-rays
  from the YOHKOH (SXT) satellite were taken into account. This work is
  connected to the SOHO EIT Proposal Brajsas.

---------------------------------------------------------
Title: Determination of the Solar Rotation Tracing EUV Bright Points
    with the Automatic Method
Authors: Wöhl, H.; Brajša, R.; Vršnak, B.; Ruždjak, V.; Clette,
   F.; Hochedez, J. -F.
2001HvaOB..25...27W    Altcode:
  Full-disc solar images in the extreme ultraviolet part of the spectrum
  from the SOHO spacecraft (instrument EIT, data in the spectral
  line of Fe XV at the wavelength of 28.4 nm) are used for the solar
  rotation determination tracing coronal bright points. From the time
  differences in tracer positions, approximately six hours, the solar
  rotation velocity is determined automatically for image sequences in
  several time intervals from June 4, 1998 to May 22, 1999. The resulting
  rotational profiles are mutually compared.

---------------------------------------------------------
Title: Determination of the Solar Rotation Tracing EUV Bright Points
    with the Interactive Method
Authors: Brajša, R.; Wöhl, H.; Schuck, T. J.; Schawinski-Guiton,
   K.; Wegner, A.; Vršnak, B.; Ruždjak, V.; Clette, F.; Hochedez, J. -F.
2001HvaOB..25...13B    Altcode:
  Full-disc solar images in the extreme ultraviolet part of the spectrum
  from the SOHO spacecraft (instrument EIT, data in the spectral line of
  Fe XV at a wavelength of 28.4 nm) are used to visually identify coronal
  bright points appropriate for the solar rotation determination. From the
  time differences in successive tracer positions, about six hours, the
  solar rotation velocity is determined tracing coronal bright points in
  several time intervals from June 4, 1998 to May 22, 1999. The resulting
  rotational profiles obtained by five observers are mutually compared.

---------------------------------------------------------
Title: Statistical Study of Solar Flares Observed in Soft X-Ray,
    Hard X-Ray and Hα Emission
Authors: Veronig, A.; Vršnak, B.; Temmer, M.; Magdalenić, J.;
   Hanslmeier, A.
2001HvaOB..25...39V    Altcode:
  Correlations among statistical properties of solar flares observed
  in soft X-rays, hard X-rays and Hα are studied. We investigate
  corresponding HXR flares measured by BATSE, SXR flares observed by GOES
  and Hα flares reported in the SGD for the period 1997--2000. Distinct
  correlations are found among the SXR peak flux and Hα area, as well
  as between the SXR peak flux and HXR fluence. This can be comprehended
  in the frame of the chromospheric evaporation model of flares.

---------------------------------------------------------
Title: Statistical Weights and Selective Height Corrections in the
    Determination of the Solar Rotation Velocity
Authors: Brajša, R.; Ruždjak, V.; Vršnak, B.; Wöhl, H.;
   Pohjolainen, S.; Upro, S.
2000SoPh..196..279B    Altcode:
  Observations of the Sun performed at 37 GHz with the 14-m radio
  telescope of the Metsähovi Radio Observatory were analyzed. Rotation
  velocities were determined, tracing Low Temperature Regions (LTRs) in
  the years 1979-1980, 1981-1982, 1987-1988, and 1989-1991. Statistical
  weights were ascribed to the determined rotation velocities of LTRs,
  according to the number of tracing days. Measured changes of the
  rotation velocity during the solar activity cycle, as well as a
  north-south rotation asymmetry, are discussed. The results obtained
  with and without the statistical weights procedure are compared, and it
  was found that the statistical significance of the solar differential
  rotation parameters' changes is higher when the statistical weights
  procedure is applied. A selective application of the height correction
  on LTR's positions has not removed the cycle-related changes nor the
  north-south asymmetry of the solar rotation measured tracing LTRs. So,
  projection effects cannot explain these changes. The differential
  rotation of LTRs is more rigid than the differential rotation obtained
  tracing magnetic features and measuring Doppler shifts, which can be
  explained by the association rate of the LTRs' positions with rigidly
  rotating `pivot points'. The observed cycle-related changes and the
  north-south asymmetry of the rotation velocity of LTRs are consistent
  with the cycle-related changes and the north-south asymmetry of the
  association rate between LTRs and pivot points.

---------------------------------------------------------
Title: Formation of coronal MHD shock waves - II. The Pressure
    Pulse Mechanism
Authors: Vršnak, B.; Lulić, S.
2000SoPh..196..181V    Altcode:
  The ignition of coronal shock waves by flares is investigated. It
  is assumed that an explosive expansion of the source region caused
  by impulsive heating generates a fast-mode MHD blast wave which
  subsequently transforms into a shock wave. The solutions of 1-D
  MHD equations for the flaring region and for the external region
  are matched at their boundary. The obtained results show under what
  conditions flares can ignite shock waves that excite the metric type
  II bursts. The heat input rate per unit mass has to be sufficiently
  high and the preflare value of the plasma parameter β in the flaring
  region has to be larger than β<SUB>0</SUB><SUP>crit</SUP>. The critical
  values depend on the flare dimensions and impulsiveness. Larger and more
  impulsive flares are more effective in generating type II bursts. Shock
  waves of a higher Mach number require a higher preflare value of β
  and a more powerful heating per unit mass. The results demonstrate why
  only a small fraction of flares is associated with type II bursts and
  why the association rate increases with the flare importance.

---------------------------------------------------------
Title: Formation Of Coronal Mhd Shock Waves - I. The Basic Mechanism
Authors: Vršnak, B.; Lulić, S.
2000SoPh..196..157V    Altcode:
  The formation and evolution of a large amplitude MHD perturbation
  propagating perpendicular to the magnetic field in a perfectly
  conducting low β plasma is studied. The perturbation is generated
  by an abrupt expansion of the source region. Explicit expressions
  for the time and the distance needed for the transformation of the
  perturbation's leading edge into a shock wave are derived. The results
  are applied to coronal conditions and the dynamic spectra of the radio
  emission excited by the shock are synthesized, reproducing metric and
  kilometric type II bursts. The features corresponding to the metric
  type II burst precursor and the moving type IV burst in the case of
  kilometric type II bursts are identified. A specific radio signature
  that is sometimes observed at the onset of a metric type II burst is
  found to appear immediately before the shock wave formation due to
  the associated growth of the magnetic field gradient. Time delays and
  starting frequencies of bursts' onsets are calculated and presented
  as a function of the impulsiveness of the source-region expansion,
  using different values of the ambient Alfvén velocity and various time
  profiles of the expansion velocity. The results are confronted with
  the observations of metric and kilometric type II solar radio bursts.

---------------------------------------------------------
Title: Characteristics of Flares with Hα Emission Protruding over
    Major Sunspot Umbrae
Authors: Vršnak, B.; Ruždjak, V.; Brajša, R.; Zlobec, P.; Altaş,
   L.; Özgüç, A.; Aurass, H.; Schroll, A.
2000SoPh..194..285V    Altcode:
  A sample of 47 importance ≥ 1 flares whose Hα emission occurred
  or protruded over umbrae of major sunspots (so called Z-flares) was
  studied to investigate characteristics of the associated dm - m radio,
  microwave and soft X-ray emission as the energy release site permeats
  into regions of strong magnetic fields. A close time association was
  found between the microwave burst peak and the `contact' of the Hα
  emission with the sunspot umbra. The Hα emission attained maximum
  close to or a few minutes after the contact. The soft X-ray bursts
  were delayed more, attaining maximum 0-10 min after the contact. The
  onset of bursts in the dm - m wavelength range was associated with the
  period of growth or the peak of the microwave burst. Two categories
  of type III and IV bursts could be recognized: the ones starting some
  ten minutes before the microwave peak, and those that begin close to
  the microwave burst peak. Type III bursts occur preferably when the
  microwave burst peaks simultaneously with or after the contact. The
  results are explained presuming that the contact reveals a permeation
  of the energy release process into a region of strong magnetic fields,
  where the process intensifies, and where the accelerated particles
  have access to magnetic field lines extending to large coronal
  heights. Different manifestations of the energy release process in
  various magnetic field topologies are considered to account for the
  various time sequences observed.

---------------------------------------------------------
Title: Correlations Between Properties of Type II Bursts and
    Associated Flares
Authors: Magdalenic, J.; Vrsnak, B.
2000HvaOB..24....1M    Altcode:
  Relations between characteristics of metric type II bursts and the
  associated microwave bursts are investigated to test the model of the
  shock wave formation via a flare ignited blast. It is found that the
  time delay of the type II burst start after the onset of the microwave
  burst is shorter for a more powerful microwave burst. A considerably
  lower correlation coefficient is found for the microwave burst
  impulsiveness. The starting frequency of a type II burst increases
  with the microwave burst impulsiveness. The instantaneous relative
  bandwidths and the propagation velocities are positively correlated,
  and are larger when associated with stronger microwave bursts. All of
  the obtained correlations are fully consistent with the flare ignited
  blast wave scenario for the shock wave formation.

---------------------------------------------------------
Title: Position Measurements on Synoptic Solar Images
Authors: Rosa, D.; Hrzina, D.; Vrsnak, B.; Brajsa, R.
2000HvaOB..24..145R    Altcode:
  Procedures for finding the solar sidereal rotation rate, which are
  taking into account the height of tracers are described. The related
  algorithms for data reduction, including detailed corrections for the
  Earth's motion, are presented.

---------------------------------------------------------
Title: On the Origin and Propagation of Coronal and Interplanetary
    MHD Shock Waves
Authors: Vrsnak, B.; Lulic, S.
2000HvaOB..24...17V    Altcode:
  Various scenaria for the formation of coronal and interplanetary MHD
  shock waves are surveyed. The main characteristics of shocks generated
  by different mechanisms are summarized and observational signatures are
  illustrated by several examples. An explanation is proposed showing
  how a flare ignited shock can sustain in propagating through the
  interplanetary space. Signatures that might reveal the shock source
  and the shock formation mechanisms are discussed.

---------------------------------------------------------
Title: Measurements of Solar Rotation Using EUV Bright Points -
    Preliminary Results
Authors: Brajsa, R.; Woehl, H.; Kasabasic, M.; Rodmann, J.; Vrsnak,
   B.; Ruzdjak, V.; Rosa, D.; Hrzina, D.; Clette, F.; Hochedez, J. -F.
2000HvaOB..24..153B    Altcode:
  Full-disc solar images in the extreme ultraviolet part of the spectrum
  from the SOHO spacecraft (instrument EIT, data in the spectral line
  of Fe XV at the wavelength of 28.4 nm) are used to identify visually
  various small-scale coronal structures appropriate for the determination
  of the solar rotation. From the time differences in tracer positions,
  approximately six hours, the solar rotation velocity is determined
  tracing coronal bright points in the period June 4-14, 1998 by four
  observers. The resulting rotational profiles are mutually compared
  and the reduction methods are discussed.

---------------------------------------------------------
Title: Correlated Radio Bursts Observed at Metric and Millimetric
    Wavelengths
Authors: Zlobec, P.; Urpo, S.; Vrsnak, B.; Brajsa, R.; Ruzdjak, V.
2000HvaOB..24...41Z    Altcode:
  Characteristics of the bursts that occur almost contemporaneously at
  metric and millimetric wavelengths are presented. It is found that
  such events are rather rare. The correlated impulsive bursts observed
  at 237 MHz and at 37 GHz start in average almost simultaneously (time
  difference 0.3 - 2.8 s). The first peaks at 37 GHz are delayed few
  seconds (3.1 - 3.0 s) in respect to the 237 MHz peaks, whereas for the
  bursts maxima the delay is about 1s in average (1.0 - 2.7 s). A weak
  correlation between peak fluxes at 37 GHz and 237 MHz is found. Spectral
  characteristics of these events indicate electron beams of extremely
  high energies. The association of the gradual bursts observed at 37
  GHz and the phenomena at 237 MHz is not so clear, however in some
  cases a relationship was established.

---------------------------------------------------------
Title: Flares in Sigmoidal Coronal Structures   a Case Study
Authors: Aurass, H.; Vršnak, B.; Hofmann, A.; Rudžjak, V.
1999SoPh..190..267A    Altcode:
  We analyze radio observations, magnetograms and extrapolated field
  line maps, Hα filtergrams, and X-ray observations of two flare events
  (6 February 1992 in AR 7042 and 25 October 1994 in AR 7792) and study
  properties, evolution and energy release signatures of sigmoidal loop
  systems. During both events, the loop configuration seen in soft X-ray
  (SXR) images changes from a preflare sigmoidal shape to a relaxed
  post-flare loop system. The underlying magnetic field system consists
  of a quadrupolar configuration formed by a sheared arcade core and
  a remote field concentration. We demonstrate two possibilities: a
  sigmoidal SXR pattern can be due to a single continuous flux tube (the
  1992 event). Alternatively, it can be due to a set of independent loops
  appearing like a sigmoid (the 1994 event). In both cases, the preflare
  and post-flare loops can be well reproduced by a linear force-free
  field and potential field, respectively, computed using preflare
  magnetograms. We find that thermal and non-thermal flare energy release
  indicators of both events become remarkably similar after applying
  spatial and temporal scale transformations. Using the spatial scaling
  between both events we estimated that the non-thermal energy release
  in the second event liberated about 1.7 times more energy per unit
  volume. A two-and-a-half times faster evolution indicates that the rate
  of the energy release per unit volume is more than four times higher
  in this event. A coronal type II burst reveals ignition and propagation
  of a coronal shock wave. In contrast, the first event, which was larger
  and released about a 10 times more energy during the non-thermal phase,
  was associated with a CME, but no type II burst was recorded. During
  both events, in addition to the two-ribbon flare process an interaction
  was observed between the flaring arcade and an emerging magnetic flux
  region of opposite polarity next to the dominant leading sunspot. The
  arcade flare seems to stimulate the reconnection process in an `emerging
  flux-type' configuration, which significantly contributes to the energy
  release. This regime is characterized by the quasiperiodic injection of
  electron beams into the surrounding extended field line systems. The
  repeated beam injections excite pulsating broadband radio emission in
  the decimetric-metric wavelength range. Each radio pulse is due to a
  new electron beam injection. The pulsation period (seconds) reflects
  the spatial scale of the emerging flux-type field configuration. Since
  broadband decimetric-metric radio pulsations are a frequent radio
  flare phenomenon, we speculate that opposite-polarity small-scale flux
  intrusions located in the vicinity of strong field regions may be an
  essential component of the energy release process in dynamic flares.

---------------------------------------------------------
Title: Height of Tracers and the Correction of the Measured Solar
Synodic Rotation Rate: Demonstration of the Method
Authors: Vršnak, B.; Roša, D.; Božić, H.; Brajša, R.; Ruždjak,
   V.; Schroll, A.; Wöhl, H.
1999SoPh..185..207V    Altcode:
  Two large stable solar filaments were used as test tracers to determine
  the apparent synodic rotation rate as a function of the central meridian
  distance for several filaments' segments at different heights. An
  analytic fitting procedure was applied to determine simultaneously
  the real synodic rotation rate and the height of the traced filament
  segments. The determined heights were compared with the values obtained
  from the widths of filament contours on the solar disk and with the
  values obtained by direct measurements at the solar limb. Furthermore,
  the obtained rotation rates and heights of the filaments' segments close
  to the filaments' pivot points were compared with the values obtained
  using two successive central meridian passages. Finally, sources and
  scales of errors were investigated and possible implications on the
  previous studies of the solar differential rotation were considered.

---------------------------------------------------------
Title: An Estimate of Microwave low-Brightness-Temperature Regions'
    Heights Obtained Measuring Their Rotation Velocity
Authors: Brajša, R.; Ruždjak, V.; Vršnak, B.; Wöhl, H.;
   Pohjolainen, S.; Urpo, S.
1999SoPh..184..281B    Altcode:
  Daily full-disk solar maps obtained at 37 GHz in the years 1979,
  1980, 1981, 1982, 1987, 1988, 1989, 1990, and 1991 are analysed
  and compared with full-disk solar maps in Hα. A search for a
  difference in the measured angular rotation velocity for two classes
  of microwave low-brightness-temperature regions (LTRs), associated and
  not associated with Hα filaments, is performed. Procedures with and
  without statistical weights, assigned to angular rotation velocities
  according to the tracing time, are applied and the statistical
  significance of the results is discussed. A higher angular rotation
  velocity is measured for LTRs associated with Hα filaments than for
  the not-associated ones. This angular velocity difference is interpreted
  as a consequence of a height difference between these two types of LTR
  tracers. Changes of the solar differential rotation velocity during
  the activity cycle measured using LTRs as tracers are explained by
  the measured cycle-dependence of the association rate between LTRs
  and Hα filaments. Similarly, the north-south asymmetry in the solar
  rotation velocity measured tracing LTRs is explained by the measured
  north-south asymmetry in the association rate between LTRs and Hα
  filaments. The rotation velocity of LTRs and Hα filaments is on the
  average more rigid in comparison with sunspots.

---------------------------------------------------------
Title: An analysis of the solar rotation velocity determined tracing
    microwave features and an estimate of their heights.
Authors: Brajša, R.; Ruždjak, V.; Vršnak, B.; Wöhl, H.;
   Pohjolainen, S.; Urpo, S.
1999joso.proc..156B    Altcode:
  Measurements of the Sun performed at 37 GHz (8 mm) with the 14 m
  radio telescope of the Metsähovi Radio Observatory were analysed
  and rotation velocities tracing microwave Low brightness Temperature
  Regions in the years 1979 - 1980, 1981 - 1982, 1987 - 1988, and 1989 -
  1991 were determined. The statistical weights method was applied and
  possible changes of the measured rotation velocity values are discussed.

---------------------------------------------------------
Title: Multi-Frequency Observations of the February 6, 1992 Flare
Authors: Ruzdjak, V.; Vrsnak, B.; Aurass, H.; Hofmann, A.; Schroll, A.
1999HvaOB..23....1R    Altcode:
  Observations of the two-ribbon flare of February 6, 1992 which occured
  in the active region NOAA 7042 involving a sigmoidal soft X-ray loop
  pattern, are described. YOHKOH SXT images, H-alpha filtergrams and
  coronal magnetic field extrapolations are used to reveal details of
  the preflare coronal magnetic field configuration. The development of
  the flare in SXR, H-alpha and dm-m radio wavelength range is followed
  in detail to disclose the basic stages of the energy release process.

---------------------------------------------------------
Title: Energy Release Stages of the Complex Solar Flare of October
    25, 1994
Authors: Vrsnak, B.; Aurass, H.; Ruzdjak, V.; Hofmann, A.; Schroll, A.
1999HvaOB..23...15V    Altcode:
  The morphology and evolution of the 1n/C4.7 flare which occured in
  the active region NOAA 7792 on October 25, 1994 are studied using the
  observations in the SXR, optical and radio range. The preflare coronal
  magnetic field structure is inferred comparing the force-free magnetic
  field extrapolations of the photospheric longitudinal magnetograms
  with structures seen in YOHKOH SXT images and H-alpha filtergrams. The
  preflare arcade consisted of a highly sheared system of loops which was
  abruptly transformed during the impulsive energy release. The further
  evolution was basically following the two-ribbon flare scenario,
  including a protrusion of the energy release process into the strong
  magnetic field of the major sunspot, as well as an interaction with
  an emerging flux region.

---------------------------------------------------------
Title: A Method to Determine the Solar Synodic Rotation Rate and
    the Height of Tracers
Authors: Roša, D.; Vršnak, B.; Božić, H.; Brajša, R.; Ruždjak,
   V.; Schroll, A.; Wöhl, H.
1998SoPh..179..237R    Altcode:
  The dependence of the measured apparent synodic solar rotation rate
  on the height of the chosen tracer is studied. A significant error
  occurs if the rotation rate is determined by tracing the apparent
  position of an object above the photospheric level projected on the
  solar disc. The centre-to-limb variation of this error can be used to
  determine simultaneously the height of the object and the true synodic
  rotation rate. The apparent (projected) heliographic coordinates
  are presented as a function of the height of the traced object and
  the coordinates of its `footpoint'. The relations obtained provide
  an explicit expression for the apparent rotation rate as a function
  of the observed heliographic coordinates of the tracer, enabling an
  analytic least-squares fit expression to determine simultaneously the
  real synodic rotation rate and the height of the tracer.

---------------------------------------------------------
Title: Prominence Eruptions (Review)
Authors: Vrsnak, B.
1998ASPC..150..302V    Altcode: 1998npsp.conf..302V; 1998IAUCo.167..302V
  No abstract at ADS

---------------------------------------------------------
Title: On the Possible Changes of the Solar Differential Rotation
    during the Activity Cycle Determined Using Microwave Low-Brightness
    Regions and Hα Filaments as Tracers
Authors: Brajša, R.; Ruždjak, V.; Vršnak, B.; Pohjolainen, S.;
   Urpo, S.; Schroll, A.; Wöhl, H.
1997SoPh..171....1B    Altcode:
  The solar rotation rate obtained using the microwave
  Low-brightness-Temperature Regions (LTRs) as tracers in the heliographic
  range ± 55° from the years 1979-1980, 1981-1982, 1987-1988, and
  1989-1991 varied from 3% to 4% in medium latitudes, and below 1%
  at the equator. Using Hα filaments as tracers at higher latitudes
  from the years 1979, 1980, 1982, 1984, and 1987, the solar rotation
  rate variation was between 2% and 8%. This represents an upper limit
  on the rotation rate variation during the solar activity cycle. Such
  changes could be caused by short-lived, large-scale velocity patterns
  on the solar surface. The Sun revealed a higher rotation rate on the
  average during the maxima of the solar activity cycles 21 and 22,
  i.e., in the periods 1979-1980 and 1989-1991, respectively, which
  differs from the rotation rates (lower on the average) in some years,
  1981-1982 and 1987-1988, between the activity maximum and minimum
  (LTR data). Simultaneous comparison of rotation rates from LTRs and
  Hα filament tracings was possible in very limited time intervals
  and latitude bands only, and no systematic relationship was found,
  although the rotation rates determined by LTRs were mostly smaller than
  the rotation rates determined by Hα filaments. The errors obtained by
  applying different fitting procedures of the LTR data were analyzed, as
  well as the influence of the height correction. Finally, the north-south
  asymmetry in the rotation rate investigated by LTRs indicates that
  the southern solar hemisphere rotated slower in the periods under
  consideration, the difference being about 1%. The reliability of all
  obtained results is discussed and a comparison with other related
  studies was performed.

---------------------------------------------------------
Title: Soft X-ray, Microwave and He I Measurements of Coronal Holes
Authors: Brajsa, R.; Ruzdjak, V.; Vrsnak, B.; Pohjolainen, S.; Urpo,
   S.; Sakurai, T.; Wohl, H.
1997IAUJD..19E..15B    Altcode:
  The Poster presents and describes microwave signatures of three
  coronal holes that were recorded on May 27, 1993. Differences in the
  brightness temperatures between an equatorial and two polar coronal
  holes were found. The measurements in the He I 10830 AA absorption
  line for that day were also analyzed and compared with the microwave
  and soft X-ray data.

---------------------------------------------------------
Title: On the Determination of the Height of Microwave Low Temperature
    Regions from Solar Rotation Measurements
Authors: Brajsa, R.; Ruzdjak, V.; Vrsnak, B.; Pohjolainen, S.; Urpo,
   S.; Woehl, H.
1997HvaOB..21...67B    Altcode:
  A larger angular rotation velocity was measured for microwave LTRs
  associated with H-alpha filaments than for the not associated ones. This
  implies that LTRs not associated with H-alpha filaments are located
  at lower heights above the solar photosphere than LTRs associated with
  H-alpha filaments. Data from three intervals were analysed (1979-1980,
  1981-1982 and 1987-1988) with different percentages of association
  between LTRs and H-alpha filaments.

---------------------------------------------------------
Title: Sunspot activity and tree growth in Northern Croatia.
Authors: Vršnak, B.; Božić, H.; Roša, J.; Roša, D.; Korica, S.
1997joso.proc...91V    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Correlation of Impulsive Microwave Bursts with Type M Bursts
    and Solar Flares
Authors: Ruzdjak, V.; Vrsnak, B.; Pohjolainen, S.; Urpo, S.; Urbarz,
   H. W.
1996ASPC...93..381R    Altcode: 1996ress.conf..381R
  No abstract at ADS

---------------------------------------------------------
Title: A New Method for Numerical Data Reduction of Solar Microwave
    Measurements
Authors: Brajsa, R.; Ruzdjak, V.; Vrsnak, B.; Woehl, H.; Pohjolainen,
   S.; Urpo, S.
1996HvaOB..20...15B    Altcode:
  Numerical data reduction of full-disk solar measurement taken in
  the microwave part of the spectrum (37 GHz) at the Metsahovi Radio
  Research Station is described. The basic parameter distinguishing
  between various features on the microwave solar maps is the brightness
  temperature. Regions on the Sun with a lower brightness temperature
  than the quiet Sun level are called Low Temperature Regions (LTRs),
  and in the present paper mainly LTRs are considered. On the other
  hand, High Temperature Regions (HTRs) have a brightness temperature
  higher than the quiet Sun level. The data reduction includes: to
  obtain a circular solar picture, to construct twelve radial vectors
  from the preliminary solar disk center in order to determinate the
  coordinates of the solar limb, to remove "erroneous" limb points,
  to determine a circle trough the limb points by the least-squares
  method, to obtain corrected coordinates of the solar disk center and
  the radius and to repeat the procedures using the obtained results
  as input parameters. The quiet Sun level was determined as the mean
  value of all data points on the disk for every map separately. Several
  numerical criteria were tested, and the minima of relative intensities
  for all data points were determined. Taking these minima as centers,
  circles of different radii were drawn with criterion that the mean value
  inside the circle is less than the quiet Sun level. The latitudinal
  distribution of LTRs, as well as the solar rotation rate as determined
  by the LTRs, were investigated using automatic numerical procedures. It
  was established how the parameters which describe the solar rotation
  rate and corresponding errors depend upon various numerical criteria
  including: definition of LTR's size, allowing different deviations
  of LTR's positions and rotation rate, confining the set of obtained
  rotation rates according to each error of the rotation rate and
  confining the set of obtained rotation rates according to allowance
  of a specific rotation rate at a specific latitude.

---------------------------------------------------------
Title: Helium 10830 Å measurements of the Sun
Authors: Brajša, R.; Pohjolainen, S.; Ruždjak, V.; Sakurai, T.;
   Urpo, S.; Vršnak, B.; Wöhl, H.
1996SoPh..163...79B    Altcode:
  Measurements of the Sun in the near-infrared He I 10830 Å absorption
  line were performed using the echelle spectrograph with a dispersion
  of 6.71 mÅ per pixel at the Vacuum Tower Telescope (German Solar
  Telescopes, Teide Observatory, Izaña, Tenerife, Spain) on May 26,
  1993. These measurements were compared with full-disc soft X-ray images
  of the Sun (Japanese solar satellite Yohkoh), full-disc solar images
  in Hα (Big Bear Solar Observatory), full-disc solar images in the
  He I 10830 Å line (National Solar Observatory, Kitt Peak) and with
  full-disc microwave solar maps at 37 GHz (Metsähovi Radio Research
  Station). In the He 10830 Å line the Sun displays a limb darkening
  similar to that in the visible part of the spectrum. Active regions
  and Hα filaments show a strong absorption in the He 10830 Å line,
  whereas the absorption is weak in coronal holes.

---------------------------------------------------------
Title: Soft X-ray radiation associated with flares developing in
    strong magnetic fields.
Authors: Vršnak, B.; Ruždjak, V.; Altas, L.; Özgüç, A.; Zlobec, P.
1996joso.proc..165V    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: The Relation between the Synodic and Sidereal Rotation Period
    of the Sun
Authors: Roša, D.; Brajša, R.; Vršnak, B.; Wöhl, H.
1995SoPh..159..393R    Altcode:
  The relation between the synodic and sidereal rotation period of
  the Sun for an arbitrary date of observation is derived taking into
  account details of the Earth's motion. The transformation procedure
  between the synodic (apparent) and sidereal rotation period presented
  here can be performed without using the annual ephemerides.

---------------------------------------------------------
Title: Ignition of MHD Shocks Associated with Solar Flares
Authors: Vrsnak, B.; Ruzdjak, V.; Zlobec, P.; Aurass, H.
1995SoPh..158..331V    Altcode:
  We have selected single frequency recordings of 28 `high-frequency'
  type II bursts characterized by a starting frequency greater than
  237 MHz to estimate as accurately as possible the `launch-time' of
  the flare-associated MHD shocks. We established the time associations
  between metric type II burst onsets and the time characteristics of
  the microwave and X-ray fluxes of the associated flares. The associated
  flares were impulsive events with rise times most often about 1 min in
  the hard X-ray range and 1-2 min in the microwave wavelength range. The
  majority of the type II bursts from our sample started about 1 min
  after the maximum of the microwave burst. Launch times of MHD shocks
  producing type II bursts were obtained using the 10 × Saito coronal
  model and shock velocities estimated from burst characteristics at
  different frequencies. Back-extrapolations of type II recordings
  indicate that MHD shocks are launched in the time interval prior to
  the maximum of the first peak in the associated microwave burst, most
  probably at the beginning of the rapid increase of the microwave burst.

---------------------------------------------------------
Title: Projected Heliographic Coordinates of Objects Located in the
    Solar Atmosphere
Authors: Rosa, D.; Vrsnak, B.; Bozic, H.
1995HvaOB..19...23R    Altcode:
  The relation between the real and apparent (projected) heliographic
  coordinates of an object located in the solar atmosphere is presented
  as a function of the object's height relative to the solar surface.The
  derived relations are expressed in a explicit form providing simple
  algorhytms which can be applied to various problems in solar research,
  e.g. the solar rotation, the geometry of the coronal features, motions
  in coronal structures, etc.

---------------------------------------------------------
Title: An Investigation of Cycle-Related Changes of the Solar Rotation
    by Tracing Microwave Low Brightness Temperature Regions
Authors: Brajsa, R.; Ruzdjak, V.; Vrsnak, B.; Pohjolainen, S.; Urpo,
   S.; Woehl, H.
1995HvaOB..19....1B    Altcode:
  Indications of possible changes of the solar rotation rate during
  several phases of the solar activity cycle (the years analyzed were
  1979, 1980, 1981, 1982, 1987, 1988, 1989, 1990 and 1991) were found. The
  solar rotation rates were determined by tracing microwave Low brightness
  Temperature Regions in the latitude range 55 deg. These changes of the
  rotation rate, although of low statistical significance, indicate that
  the Sun has nearly equal rotation rates during successive cycle maxima,
  which are different from the measured rotation rates in the periods
  between the maxima.

---------------------------------------------------------
Title: Soft X-Ray Radiation Associated with Flares Developing in
    Strong Magnetic Fields
Authors: Vrsnak, B.; Ruzdjak, V.; Altas, L.; Ozguc, A.; Zlobec, P.
1995HvaOB..19...15V    Altcode:
  A sample of 30 Imp =1 Z-flares (H alpha flare emission protruding over
  sunspot umbrae) observed at Kandilli Observatory was analyzed. It was
  found that the soft X-ray emission reached its maximum approximately
  3-4 minutes after the chromospheric flare emission has protruded over
  the umbra. It can be concluded that the most powerful energy release
  takes place when the flare process starts to occure in strong magnetic
  field regions. This interpretation is also supported by the fact that
  the peaks of microwave emission at about 3 GHz (revealing the presence
  of accelerated electrons) were grouped approximately about the time
  of the protrusion. A positive correlation was found between the peak
  fluxes of the soft X-ray bursts and the magnetic field strengths of
  the protruded spots.

---------------------------------------------------------
Title: Interaction of Two Intertwined Helicoidal Current Filaments
Authors: Lulic, S.; Vrsnak, B.; Rosa, D.
1994HvaOB..18...29L    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Solar Centre-to-Limb Functions in Optical and Radio Wavelength
    Ranges
Authors: Brajsa, R.; Ruzdjak, V.; Vrsnak, B.; Pohjolainen, S.; Urpo,
   S.; Woehl, H.
1994HvaOB..18....9B    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Prominence Oscillations and Stability
Authors: Vrsnak, B.; Ruzdjak, V.
1994scs..conf..329V    Altcode: 1994IAUCo.144..329V
  A number of high-amplitude prominence oscillations of different modes,
  triggered by various perturbations, are presented and classified
  as membrane-like, string-like, sausage-like and elastic-spring-like
  oscillations.

---------------------------------------------------------
Title: Interaction of Two Intertwined Helicoidal Magnetic Tubes
Authors: Lulić, S.; Vršnak, B.; Roša, D.
1994HvaOB..18...21L    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: The Relation Between Solar Activity Tree Growth in Northern
    Croatia
Authors: Rosa, J.; Rosa, D.; Bozic, H.; Vrsnak, B.
1994HvaOB..18...21R    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Structure and Stability of Helicoidal Magnetic Structures in
    the Solar Corona
Authors: Vrsnak, B.; Ruzdjak, V.
1994HvaOB..18....1V    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: A comparison of large-scale patterns outlined by low brightness
    temperature microwave regions and magnetic fields on the Sun
Authors: Brajša, R.; Pohjolainen, S.; Ruždjak, V.; Teräsranta,
   H.; Urpo, S.; Vršnak, B.; Wöhl, H.
1994smf..conf...62B    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: The Relation Between Solar Activity and Tree Growth in
    Northern Croatia
Authors: Roša, J.; Roša, D.; BožiĆ, H.; Vršnak, B.
1994HvaOB..18...29R    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Structure and stability of helicoidal magnetic configurations
    in the solar corona
Authors: Vršnak, B.; Ruždjak, V.
1994smf..conf..393V    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Kinematics and evolution of twist in the eruptive prominence
    of August 18, 1980
Authors: Vrsnak, B.; Ruzdjak, V.; Rompolt, B.; Rosa, D.; Zlobec, P.
1993SoPh..146..147V    Altcode:
  The prominence which erupted at the SE limb on August 18, 1980 is one
  of the best observed disparition brusque events: high-resolution
  monochromatic ground-based observations in the Hα line were
  supplemented by the SMM and Solwind satellite coronographic
  observations; the radio wavelength range was well covered by
  single-frequency and spectral observations, and the prominence magnetic
  fields were measured two days before the eruption.

---------------------------------------------------------
Title: Changes of Helical Structures During the Eruption of Two
    Prominences
Authors: Rosa, D.; Vrsnak, B.; Ruzdjak, V.; Ozguc, A.; Rusin, V.
1993HvaOB..17...15R    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Erratum: "Variations of solar global rotation during the
    polarity reversal" [Hvar Obs. Bull., Vol. 16, No. 1, p. 13 - 22
    (1992)].
Authors: Brajša, R.; Vršnak, B.; Ruždjak, V.; Božić, H.;
   Pohjolainen, S.; Teräsranta, H.; Urpo, S.
1993HvaOB..17...65B    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Classification of Prominence Oscillations
Authors: Vrsnak, B.
1993HvaOB..17...23V    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Magnetic structure of solar prominences.
Authors: Vrsnak, B.
1992AnGeo..10..344V    Altcode: 1992AnG....10..344V
  The cold and dense prominence plasma is suspended in the core of
  an arcade of magnetic field lines above the solar photosphere. The
  observations reveal a rather uniform horizontal component of the
  magnetic field, predominantly directed close to the prominence long
  axis. On the other hand, monochromatic observations of the prominence
  fine structure provide a visualization of the magnetic configuration in
  the core of an arcade revealing intricate morphological structures and
  chaotic plasma flows. Prominences are usually modelled in cylindrical
  or slab geometry, assuming that the fine structure is only superposed
  on a larger scale magnetic field structure. MHD models often treat a
  prominence as a 2-D static feature but it seems that 3-D dynamical
  models, including real geometry, are necessary to comprehend the
  prominence phenomenon completely. The models predict a number of
  possible MHD instabilities which can cause a prominence eruption. When
  the critical conditions in an arcade are met the large scale magnetic
  structure erupts, together with the embedded prominence, and this
  eruption is known as a coronal mass ejection.

---------------------------------------------------------
Title: Variations of Solar Global Rotation During the Polarity
    Reversal
Authors: Brajsa, R.; Vrsnak, B.; Ruzdjak, V.; Bozic, H.; Pohjolainen,
   S.; Urpo, S.; Terasranta, H.
1992HvaOB..16...13B    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: A Study on Electric Currents in a Solar Active Region -
    a Dynamo Process at a Place of Repeated Flaring
Authors: Hofmann, A.; Ruzdjak, V.; Vrsnak, B.
1992HvaOB..16...29H    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Cycle Dependent Rotation of Solar Large Scale Patterns as
    Determined from Millimeter-Range Observations
Authors: Brajsa, R.; Ruzdjak, V.; Vrsnak, B.; Jurac, S.; Pohjolainen,
   S.; Terasranta, H.; Urpo, S.
1992ASPC...27..274B    Altcode: 1992socy.work..274B
  No abstract at ADS

---------------------------------------------------------
Title: Giant Cells on the Sun Revealed by Low Temperature Microwave
    Regions?
Authors: Brajsa, R.; Vrsnak, B.; Ruzdjak, V.; Jurac, S.; Pohjolainen,
   S.; Urpo, S.; Terasranta, H.
1992HvaOB..16....1B    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Large-scale patterns on the Sun observed in the millimetric
    wavelength range
Authors: Vrsnak, B.; Pohjolainen, S.; Urpo, S.; Terasranta, H.;
   Brajsa, R.; Ruzdjak, V.; Mouradian, Z.; Jurac, S.
1992SoPh..137...67V    Altcode:
  The nature and behaviour of large-scale patterns on the solar surface,
  indicated by the areas of brightness-temperature depressions in
  the millimetric wavelength range, is studied. A large sample of 346
  individual, low-temperature regions (LTRs) was employed to provide
  reliable statistical evidence. An association of 99% was found between
  the locations of LTRs and the large-scale magnetic field inversion
  lines, and 60% of the LTRs were associated with the inversion
  line filaments. A tentative physical association with filaments is
  reconsidered, and one particularly well-observed case is presented. The
  heights of the perturbers causing brightness-temperature depressions are
  discussed. The long-term evolution of the latitudinal distribution of
  LTRs is presented in a butterfly diagram. Two belts of low-temperature
  regions outline the active region belts, shifting with them towards the
  equator during the solar activity cycle. The low-temperature region
  belts of the forthcoming cycle appear already at the maximum of the
  actual cycle at latitudes of about 55 °. The superpositions of the
  temperature minima distributions in the synoptic maps show patterns
  appearing as `giant cells' and compatible with indications inferred
  from magnetographic data. The reliability of the inferred cells is
  considered, and a statistical analysis reveals a negligible probability
  for an accidental distribution appearing in the form of giant cells.

---------------------------------------------------------
Title: Stability of Prominences Exposing Helical like Patterns
Authors: Vrsnak, B.; Ruzdjak, V.; Rompolt, B.
1991SoPh..136..151V    Altcode:
  The internal structure of prominences appearing as twisted tubes was
  studied. The sample embraced 15 stable and 13 eruptive prominences,
  exposing patterns which possibly reflect a helical configuration. The
  equivalent pitch angles (ϑ) of twisted fine structure features were
  measured. In some cases the evolution of the internal structure was
  followed and 49 independent measurements of the parameter ϑ were
  performed in total. The results are presented in the plane relating
  the parameter ϑ and the normalized prominence height. The eruptive
  prominences occupy the region characterized by ϑ &gt; 50° and h
  &gt; 0.8d, where h and d are the prominence height and the footpoint
  half-separation, respectively. All prominences characterized by h &lt;
  0.6d or by ϑ &lt; 35° were stable. Such a result is in good agreement
  with an order of magnitude treatment of the forces acting in a curved
  magnetic tube, anchored at both ends in the photosphere.

---------------------------------------------------------
Title: Calcium Plage Intensity and Solar Irradiance Variations
Authors: Vršnak, B.; Plačko, D.; Ruždjak, V.
1991SoPh..133..205V    Altcode:
  We have established a statistical relation between the facular
  contribution to the solar irradiance and the intensity of the associated
  calcium plage. For the solar irradiance data the ACRIM measurements
  were used. The quiet-Sun level of the irradiance was determined as a
  function of the time for the period studied. A sample of plages in the
  period of the solar activity minimum was selected, during the periods
  when no spots were present on the solar disc. We have expressed the
  dependence studied through the parameter C<SUB>p</SUB> in the `proxy'
  PFI concept. The parameter C<SUB>p</SUB> could be related to the plage
  intensity (I) as C<SUB>p</SUB> = 0.006I + 0.003. The mean value of
  the parameter C<SUB>p</SUB> ranged between 0.015 and 0.017 depending
  on the choice of samples.

---------------------------------------------------------
Title: Solar Differential Rotation Determined by Polar Crown Filaments
Authors: Brajša, R.; Vršnak, B.; Ruždjak, V.; Schroll, A.;
   Pohjolainen, S.; Urpo, S.; Teräsranta, H.
1991SoPh..133..195B    Altcode:
  The rotation rates obtained by tracing 124 polar crown filaments are
  presented in comparison with previous results. Higher filament rotation
  rate in polar regions was detected and discussed in terms of the various
  phenomena such as: the projection effect due to the height of measured
  tracers, the connection of polar filaments with the magnetic field
  patterns which show an increase of the rotation rate at high latitudes,
  rigid rotation of polar filaments which form pivot points, and eventual
  change of the differential rotation law during the cycle. However, when
  the height correction for an average height of 1% of the solar radius is
  applied, the filament rotation rate in polar regions decreases. Then
  the rotation law becomes: Ω(φ) = 14.45 − 0.11 sin<SUP>2</SUP>
  φ − 3.69 sin<SUP>4</SUP> φ (° day<SUP>−1</SUP>, sidereal).

---------------------------------------------------------
Title: Intensity Variations and Short Time Evolution of Solar
    Microwave Low Temperature Regions
Authors: Pohjolainen, S.; Urpo, S.; Terasranta, H.; Vrsnak, B.;
   Brajsa, R.; Ruzdjak, V.; Jurac, S.
1991HvaOB..15...21P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Rotation of large scale patterns on the solar surface as
    determined from filament and millimeter data
Authors: Pohjolainen, S.; Vršnak, B.; Teräsranta, H.; Urpol, S.;
   Brajša, R.; Ruždjak, V.; Jurač, S.; Schroll, A.
1991LNP...380..279P    Altcode: 1991IAUCo.130..279P; 1991sacs.coll..279P
  The rotation of large scale solar magnetic field patterns was studied
  using quiescent filaments and low temperature regions observed at 37
  GHz as tracers.

---------------------------------------------------------
Title: Microwave and Soft X-ray Radiation During Flares Evolving in
    Strong Magnetic Fields
Authors: Vrsnak, B.; Ruzdjak, V.; Zlobec, P.; Jurac, S.
1991HvaOB..15...11V    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Launch-times of MHD Shocks Observed as Type II Bursts
Authors: Vrsnak, B.; Zlobec, P.; Ruzdjak, V.
1991HvaOB..15....1V    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Large scale patterns on the solar surface indicated by
    microwave observations
Authors: Vršnak, B.; Pohjolainen, S.; Teräsranta, H.; Urpol, S.;
   Brajša, R.; Ruždjak, V.; Schroll, A.; Jurač, S.
1991LNP...380..282V    Altcode: 1991IAUCo.130..282V; 1991sacs.coll..282V
  A large set of observations of the Sun at 37 GHz is analysed. An
  association of 99% is found between the regions of brightness
  temperature depression and the magnetic field inversion
  lines. Observations indicate a possible existence of giant cells with
  duration of 1-2 years and a longitudinal extension up to 90°.

---------------------------------------------------------
Title: The Role of the Magnetic Field in Intensity and Geometry in
    the Type-Iii Burst Generation
Authors: Zlobec, P.; Ruždjak, V.; Vršnak, B.; Karlický, M.;
   Messerotti, M.
1990SoPh..130...31Z    Altcode:
  We study the association of type III bursts related to Hα flares
  in different magnetic environments in the period 1970-1981. Special
  attention is paid to flares which partly cover a major spot umbra
  (Z-flares). In particular we consider the location of the spots in the
  active regions and the magnetic field intensities of spots covered by
  a ribbon. The association rate with type III bursts decreases to 17%
  when the flare is located inside the bipolar pattern of a large active
  region, compared with an association rate of 54% when the flare is
  situated outside it. The association rate increases with the magnetic
  field intensity of the spot covered by Hα emission; this is most
  clearly revealed for the flares occurring outside the bipolar pattern
  of active regions. Ninety-three percent of the flare-associated type
  III burst were accompanied by 10 cm radio bursts. For the most general
  case in which a flare is developing anywhere in an active region,
  the association with type III bursts generation increases with the
  increasing magnetic field intensity of the main spot of the group.

---------------------------------------------------------
Title: Eruptive instability of cylindrical prominences
Authors: Vrsnak, B.
1990SoPh..129..295V    Altcode: 1990SoPh..129..295B
  The stability of prominences and the dynamics of an eruption are
  studied. The prominence is represented by an uniformly twisted, curved,
  magnetic tube, anchored at both ends in the photosphere. Several stages
  of the eruption are analyzed, from the pre-eruptive phase and the onset
  of the instability, up to the late phases of the process. Before the
  eruption, the prominence evolves through a series of equilibrium states,
  slowly ascending either due to an increase of the electric current or
  to mass loss. The eruption starts when the ratio of the current to
  the total mass attains a critical value after which no neighbouring
  equilibrium exists. The linearized equation of motion was used to
  obtain the instability threshold, which is presented in a form enabling
  comparison with the observations. The height at which the prominence
  erupts depends on the twist, and is typically comparable with the
  footpoint half-separation. Low-lying prominences are stable even for
  large twists. The importance of the external field reconnection below
  the filament, and the mass loss through the legs in the early phases
  of the eruption is stressed. The oscillations of stable prominences
  with periods on the Alfvén time-scale are discussed. The results are
  compared with the observations.

---------------------------------------------------------
Title: Eruptive Instability of Magnetic Arcades
Authors: Vrsnak, B.
1990Ap&SS.170..141V    Altcode:
  Eruptive prominences trace disruptions of magnetic arcades in which
  they are embedded. The stability of an arcade containing an electric
  current filament at its axis is discussed. The model provides criteria
  for the onset of the eruptive instability in terms of prominence twist
  and overall geometry, i.e., the parameters which could be measured
  directly. The evolution of the eruption is analyzed, and the dependence
  of the acceleration and the pitch of field-lines on the height is
  established. The model is compared with the observations of one eruptive
  prominence where the development of helical structure was followed.

---------------------------------------------------------
Title: Solar Irradiance Variations and Nonthermal Processes in the
    Solar Atmosphere
Authors: Vrsnak, B.; Ruzdjak, V.; Zlobec, P.
1990BAICz..41..243V    Altcode:
  The association of solar irradiance decreases with flare and
  noise storm activity is analyzed. The studied irradiance dips were
  accompanied by enhanced flare activity, but increased flare activity
  did not necessarily imply the occurrence of a dip. On the other hand,
  longlasting broadband noise storm activity was always accompanied by
  an irradiance dip. An upper limit to the amplitude of the irradiance
  perturbation caused by a sunspot group of a given area and flare
  activity is estimated. Also, a lower limit to the irradiance
  perturbation amplitude with respect to noise storm activity is
  established. The estimated energies associated with the considered
  processes were found to be much smaller than the energies related to
  the irradiance decreases. Nevertheless, the analysis indicates the
  importance of nonthermal processes in large agglomerations of magnetic
  fields related to irradiance decreases.

---------------------------------------------------------
Title: Oscillatory Motions in an Active Prominence
Authors: Vrsnak, B.; Ruzdjak, V.; Brajsa, R.; Zloch, F.
1990SoPh..127..119V    Altcode:
  Different types of oscillatory motions were detected in the late
  phases of eruption of a prominence. We found oscillations of
  the prominence axis and diameter with periods of 4.3 and 9.1 min,
  corresponding to the eigenmodes m = 4 and m = 8 with a damping factor
  4.6 × 10<SUP>−3</SUP> s<SUP>−1</SUP>. A period about 4.5 min was
  found for oscillations of the pitch angle of the helically twisted
  filaments. The m = 2 and m = 3 eigenmodes could be also identified
  and they led to the final relaxation of the prominence axis. The
  observations are compared with a model in which we consider forces
  acting in a curved, cylindrical magnetic tube anchored at both ends
  in the photosphere and carrying an electric current. The stability of
  the prominence is discussed.

---------------------------------------------------------
Title: Dynamics and Internal Structure of an Eruptive Prominence
Authors: Vrsnak, B.
1990SoPh..127..129V    Altcode:
  The kinematics and the development of the internal structure in the
  eruptive prominence of August 16, 1988 are described. The prominence
  exposed helical structure, and the pitch of the fine structure filaments
  was measured. The evolution of the pitch was measured in the legs of
  the prominence and at its summit from the pre-eruptive phase up to the
  late phases of the eruption. The pitch angle was decreasing in the legs
  as well as at the summit. However, the observations indicate that the
  integral twist remained constant. The prominence was twisted more at
  the summit where it was wider than in the legs. The `effective' twist
  at the prominence summit was approximately 20 π and in the legs it
  amounted to about 8 π. Such a ratio did not change during the eruption,
  i.e., no redistribution of the twist was observed within the accuracy
  of measurements. The nature of the instability causing the eruption
  is discussed and the energetics of the process is considered.

---------------------------------------------------------
Title: Polar Crown Filaments and Solar Differential Rotation at
    High Latitudes
Authors: Brajša, R.; Vršnak, B.; Rundjak, V.; Schroll, A.
1990LNP...363..293B    Altcode: 1990doqp.coll..293B; 1990IAUCo.117..293B
  No abstract at ADS

---------------------------------------------------------
Title: Motion of High Latitude Solar Microwave Sources and Comparison
    with Polar Prominences
Authors: Urpo, S.; Pohjolainen, S.; Teräsranta, H.; Vrsnak, B.;
   Ruzdjak, V.; Brajsa, R.; Schroll, A.
1990LNP...363..292U    Altcode: 1990doqp.coll..292U; 1990IAUCo.117..292U
  Solar microwave sources at high solar latitudes have been observed
  with a 14 m radio telescope at the Metsahovi Radio Research Station in
  Finland. Several periods for observations were organized in 1986-1989
  in order to detect sources close to the north and south pole of
  the Sun. Measurements at 22 and 37 GHz (wavelengths 14 and 8 mm
  respectively) have revealed the existence of high temperature and low
  temperature regions (relative to the quiet Sun level) at latitudes 50-80
  degrees. The motions of these regions have been studied and compared
  with optical measurements of polar prominences. The temperature
  enhancement at 37 GHz is typically 100-400 K above the quiet Sun
  level (7800 K) at that frequency. Although in most cases temperature
  depression in a low temperature area amounts 50-300 K, at 37 GHz,
  the temperature drop in the low temperature area which was observed in
  July 1982 was as low as 900 K. The results of the radio measurements
  of the Sun at 22 and 37 GHz on high solar latitudes imply that high
  temperature areas correspond to polar faculae while low temperature
  areas correspond to polar prominences. The principal cause of the
  observed lower temperature area is the absorbtion by the filament.

---------------------------------------------------------
Title: Vector Magnetic Field and Currents at the Footpoint of a
    Loop Prominence
Authors: Hofmann, A.; Ruždjak, V.; Vršnak, B.
1990LNP...363..233H    Altcode: 1990IAUCo.117..233H; 1990doqp.coll..233H
  Using H -filtergrams and vector magnetograms we study the structure of
  the magnetic field at the footpoint of a loop prominence rooting deep
  in the penumbral photosphere of a sunspot. In the region investigated
  the footpoint -field is well marked in the transversal field map. The
  field has a predominantly transverse character and is directed parallel
  to the axis of the prominence. The flux bundle forming the prominence
  left the photosphere by an angle of about 26°, i.e. close to the
  horizontal. In the maps of current densities inferred from the vector
  magnetic field we find a pair of up- and downflowing currents, being
  situated symmetrically to the axis of the prominence. This indicates on
  a current ( 3,8 · 1011 A) flowing round the flux bundle and generating
  the Lorentz forces causing the concentration of flux at the footpoint
  region. The vertical gradients of the longitudinal field hint on an
  increase of the field strength with height, i.e. toward the axis of
  the prominence.

---------------------------------------------------------
Title: Time Profiles of Solar Irradiance Dips
Authors: Vrsnak, B.; Ruzdjak, V.; Ruzic, Z.
1990SoPh..125...13V    Altcode:
  ACRIM data have been analyzed to study the time profiles of simple
  irradiance dips caused by single active regions. Comparison of the
  average characteristics of the dips appearing in the minimum and maximum
  of the solar cycle shows that there are no significant differences. In
  both periods we disclosed the facular irradiance excess in the profile
  wings having typical duration of two to three days and an amplitude
  of about 20% of the dip amplitude. The profiles were asymmetric, with
  a stronger and longer excess in the trailing wing. We determined an
  `average' profile which was attributed to an idealized active region,
  and we calculated the luminosity perturbation caused by it. Excess
  radiation in the wings of the profile compensates about 1/3 of
  the deficit in the dip. In the most simple case from our sample we
  compared the profile based on ACRIM measurements and the proxy profile
  estimated using sunspot and plage areas published in Solar Geophysical
  Data catalogues. The comparison indicates that the facular excess was
  compensating instantaneously about 2/3 of the luminosity deficit caused
  by sunspots.

---------------------------------------------------------
Title: On the Appearances, Intensities and Motions of Solar Microwave
    Low Temperature Areas
Authors: Pohjolainen, S.; Brajša, R.; Urpo, S.; Teräsranta, H.;
   Vršnak, B.; Ruždjak, V.; Jurač, S.
1990PDHO....7...56P    Altcode: 1990ESPM....6...56P; 1990dysu.conf...56P
  Solar microwave sources at 37 GHz have been observed at Metsähovi since
  1978. The solar maps have revealed the existence of low temperature
  regions, i.e. areas where the brightness temperature is typically 100 -
  400K lower than the quiet Sun level, throughout the solar cycle. The
  authors have investigated the appearances, intensities and motions
  of these temperature depressions and compared them with the activity
  features in the optical part of the spectrum.

---------------------------------------------------------
Title: Oscillatory Relaxation of an Eruptive Prominence
Authors: Vršnak, B.; Ruždjak, V.; Brajša, R.; Zloch, F.
1990LNP...363..256V    Altcode: 1990IAUCo.117..256V; 1990doqp.coll..256V
  Different types of oscillatory motions were detected in the late phases
  of eruption of a prominence. We found oscillations of the prominence
  axis and diameter with periods of 4.3 and 9.1 minutes corresponding
  to the eigenmodes m=4 and m=8 with a damping factor 4.6 10-3 s{-1}. A
  period of about 4.5 minutes was found for oscillations of the pitch
  angle of the helically twisted filaments. The m=2 and m=3 eigenmodes
  could be also identified and they led to the final relaxation of the
  prominence axis. The observations are interpreted in analogy with
  damped oscillations of an elastic string. The lowest eigenmode was
  not excited due to &gt;hile the m=2 and m=3 eigenmodes were highly
  damped. The frequency of free oscillations due to restoring forces
  and the decay constant were inferred using the dispersion relation for
  oscillation of the elastic string and the observed frequentes in the
  m=4 and m=8 modes to =3.1x10-3-1, corresponding to a period of T=34
  min. and S =4.6x10-3s-1.

---------------------------------------------------------
Title: A Comparison of Hα and Soft X-Ray Characteristics of Spotless
    and SPOT Group Flares
Authors: Ruždjak, V.; Vršnak, B.; Schroll, A.; Brajša, R.
1989SoPh..123..309R    Altcode:
  A comparative analysis of spotless and spot group flares recorded
  at Hvar and Kanzelhöhe Observatories during the 21st cycle of solar
  activity is presented. The rate of occurrence of two-ribbon flares was
  found to be significantly higher for the spotless flares. In comparison
  with spot group flares of corresponding Hα importance, the soft X-ray
  peak values have been systematically lower for the spotless flares. The
  highest peak values and the energy released in soft X-rays was found
  for flares with a Hα ribbon protruding over a major spot umbra. It
  was found that the effective plasma temperatures in spotless flares
  have been considerably lower than the temperatures in spot group flares.

---------------------------------------------------------
Title: Soft X-Ray Emission from a Hot Turbulent Current Sheet and
    the Precursor Phase of Solar Flares
Authors: Vrsnak, B.
1989SoPh..120...79V    Altcode:
  The properties and development of a high-temperature current sheet
  characterized by increasing merging velocity are studied and related to
  the early phases of solar flares. It is shown that the system can be
  described by the Petschek-type geometry for a wide range of merging
  velocities. In the diffusion region and the standing MHD shocks a
  certain low-frequency plasma microturbulence is generated from the very
  beginning of the reconnection process. We present qualitative solutions
  for the case of ion-acoustic turbulence in marginally stable state,
  which provide a comparison with observations. The increasing merging
  velocity leads to the appearance of the soft X-ray precursor. The
  precursor temperature maximum should appear during the current sheet
  formation, before the Petschek regime is established. In the Petschek
  regime the temperature of the hot plasma decreases due to the decrease
  of the magnetic field strength at the diffusion region boundary, while
  the soft X-ray radiation still increases, reaching precursor maximum
  for merging velocities about 1% of the external Alfvén velocity. The
  precursor phase ends when the value of the merging velocity surpasses
  the upper limit for the Petschek regime and the system enters into the
  pile-up regime, causing a new increase of plasma temperature and soft
  X-ray radiation.

---------------------------------------------------------
Title: Motion of High Latitude Solar Microwave Sources and Comparison
    with Solar Prominences
Authors: Urpo, S.; Pohjolainen, S.; Terasranta, H.; Vrsnak, B.;
   Ruzdjak, V.; Brajsa, R.; Schroll, A.
1989HvaOB..13..437U    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Oscillatory Relaxation of an Eruptive Prominence
Authors: Vrsnak, B.; Ruzdjak, V.; Brajsa, R.; Zloch, F.
1989HvaOB..13..137V    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Polar Crown Filaments and Solar Differential Rotation at
    High Latitudes
Authors: Brajsa, R.; Vrsnak, B.; Ruzdjak, V.; Schroll, A.
1989HvaOB..13..449B    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Vector Magnetic Field and Currents at the Footpoint of a
    Loop Prominence
Authors: Hofmann, A.; Ruzdjak, V.; Vrsnak, B.
1989HvaOB..13...11H    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Solar irradiance variations and their relation with solar
    flares.
Authors: Pap, J.; Vrsnak, B.
1989sasf.confP.243P    Altcode: 1988sasf.conf..243P; 1989IAUCo.104P.243P
  A clear association is demonstrated between the dips in the total solar
  irradiance and flare occurrence. It is found that both the irradiance
  dips and flares are related to emerging new activity.

---------------------------------------------------------
Title: Structure and Stability of Prominences with Helical Structure
Authors: Vrsnak, B.; Ruzdjak, V.; Brajsa, R.; Dzubur, A.
1988SoPh..116...45V    Altcode:
  Observations of internal structure and development of four helical
  prominences are presented. We assume that the helically twisted fine
  structure threads are outlining magnetic field lines and we found
  that it is possible to describe the magnetic fields by the uniform
  twist configuration, with the twists ranging between 2π and 7π. The
  estimated lower limits for the magnetic fields were about 20 G which
  give lower limits for the currents flowing along the prominences in
  the range between 2 × 10<SUP>10</SUP> A and 2 × 10<SUP>11</SUP> A and
  current densities at the axis of the prominences about 10<SUP>-4</SUP>
  A m<SUP>-2</SUP>. The upper limit of electron drift velocity could
  be estimated as 1 m s<SUP>-1</SUP>, which is far below the critical
  velocities for the onset of plasma microinstabilities.

---------------------------------------------------------
Title: Solar Irradiance Perturbations Caused by Active Regions
Authors: Vrsnak, B.; Ruzdjak, V.; Ruzic, Z.
1988HvaOB..12....1V    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Solar irradiance variations and magnetic field emergence
Authors: Vrsnak, B.; Ruzdjak, V.
1988AdSpR...8g..35V    Altcode: 1988AdSpR...8...35V
  We have studied the association between different aspects of the
  magnetic field behaviour in large active regions and the solar
  irradiance variations. It was found that irradiance decreases were
  accompanied by enhanced flare and coronal mass ejection activity. A
  still better association seems to exist with broadband, long-lasting
  noise storm activity. This indicates that the enhanced generation
  of weak MHD shock waves causing noise storm in large interconnecting
  coronal loops is related to the appearance of irradiance dips.

---------------------------------------------------------
Title: H-alpha Flares Recorded at Hvar Observatory During the "Solar
    International Month-September 1988"
Authors: Ruzdjak, V.; Vrsnak, B.; Zloch, F.
1988HvaOB..12...11R    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Reconnection driven by an erupting filament in the May 14,
    1981 flare
Authors: Vršnak, B.; Ruždjak, V.; Messerotti, M.; Mouradian, Z.;
   Urbarz, H.; Zlobec, P.
1987SoPh..114..289V    Altcode:
  We present observations of the flare of May 14, 1981, which can
  be classified as a three-ribbon flare. After a detailed analysis
  in metric, decimetric, microwave, optical, and X-ray ranges we
  propose that the event was caused by a reconnection process driven
  by erupting filament. The energy was liberated in the current sheet
  above the filament in the region between the erupting flux and the
  overlying field. It is shown that plasma microinstabilities develop
  as the plasma enters the current sheet. The observations indicate
  that during the precursor phase a certain low-frequency turbulence,
  such as ion-accoustic turbulence had to be present.

---------------------------------------------------------
Title: Evidence for interacting loop process in a phase of the May
    16, 1981 flare
Authors: Vrsnak, B.; Ruzdjak, V.; Messerotti, M.; Zlobec, P.
1987SoPh..111...23V    Altcode:
  The behaviour of the flare in the period of enhancement and maximum of
  hard X-ray, microwave and decimetric type IV continuum is analysed. The
  elongation of the Hα ribbons and microwave source disclose that
  the energy release site was shifting through a system of loops with
  a velocity less than 200 km s<SUP>-1</SUP>, and that the energy
  was carried down the field lines with a velocity of about 1000 km
  s<SUP>-1</SUP>, implying the thermal conduction front mechanism of
  energy transport. Several processes of energy release are considered and
  it is concluded that an explanation in terms of succeeding interactions
  of neighbouring loops, involving fast reconnection of their poloidal
  components is in best agreement with the observations.

---------------------------------------------------------
Title: Spotless flares and the associated radio continuum emission.
Authors: Ruždjak, V.; Messerotti, M.; Nonino, M.; Schroll, A.;
   Vršnak, B.; Zlobec, P.
1987SoPh..111..103R    Altcode: 1987SoPh..111..103F
  We studied 24 spotless flares of Ha importance ≥ 1 which occurred
  during the 21st cycle of solar activity. The spotless flares could
  be grouped in three categories according to their location and time
  history of the associated active region. Our association of the
  flares with radio events was based on relative timing and on the
  flare importances. Weak microwave gradual rise and fall events were
  frequently recorded during the occurrence of the spotless flares. A few
  flares from our sample could be associated with impulsive and complex
  microwave bursts. Only in one case an association of a spotless flare
  with a significant metric type II/IV event seems to be justified.

---------------------------------------------------------
Title: The Effects of Diferent Basic Process in Solar Flares
Authors: Vrsnak, B.
1987HvaOB..11...91V    Altcode:
  Current flare classifications are presented briefly, to illustrate
  observational evidence of the differences among flares. Possible
  mechanisms of energy release processes in different magnetic structures
  are discussed and the interplay between ideal and resistive MHD
  processes and plasma microinstabilities is emphasized. The interacting
  loop flare model is taken as an example to show that there are
  observational evidences for at least two different mechanisms of energy
  release processes (coalescence instability and driven reconnection)
  in this kind of flares.

---------------------------------------------------------
Title: PC Based Image Processing of Solar Activity Features
Authors: Dzubur, A.; Caldarevic, M.; Ruzdjak, V.; Vrsnak, B.
1987HvaOB..11..143D    Altcode:
  A short description of digital image, i.e. the image which is after
  digitalization process stored in the PC computer memory and to which
  digital processing can be applied is given. The procedure is applied
  to images of various solar activity features.

---------------------------------------------------------
Title: Behaviour of the Polarization at Dm-M Wavelengths during the
    Evolution of Five Two-Ribbon Flares
Authors: Ruzdjak, V.; Vrsnak, B.; Zlobec, P.; Schroll, A.
1986SoPh..104..169R    Altcode:
  The general behaviour of the circular polarization at dm-m wavelengths
  during the evolution of five two-ribbon flares is investigated. The
  changes of polarization, if present, occurred 10 to 20 min after the
  impulsive phases. Increases of the radio and X-ray fluxes occurred at
  the moments when the Hα ribbons started to extend over spot umbrae.

---------------------------------------------------------
Title: Changes of Polarization in the dm-m Range During the Flare
    of May 16, 1981
Authors: Ruzdjak, V.; Vrsnak, B.; Zlobec, P.
1986HvaOB..10...11R    Altcode:
  The polarization behaviour in the dm-m radio range during the flare of
  May 16, 1981 is studied and related to other observed phenomena. The
  evolution of the flare is discussed.

---------------------------------------------------------
Title: Flare occurence in the complex of activity NOAA/USAF No. 4201,
    May 29 - June 12, 1983
Authors: Ruždjak, V.; Vršnak, B.; Hofmann, A.; Křivský, L.;
   Markova, E.; Kálmán, B.
1986CoSka..15..257R    Altcode:
  The evolution of a large complex of activity NOAA/USAF No. 4201 in the
  period May 29 to June 12, 1983 was investigated. Almost 200 flares
  occurring in the complex were reported, most of which clustered at
  preferred sites where delta configurations with shear and strong
  gradients of the magnetic fields were present or new flux emerged.

---------------------------------------------------------
Title: Microwave limb sources and their relation to solar flares
Authors: Urpo, S.; Terasranta, H.; Pohjolainen, S.; Ruzdjak, V.;
   Vrsnak, B.
1986AdSpR...6f.267U    Altcode: 1986AdSpR...6..267U
  Solar microwave maps (at 22 and 37 GHz) performed at Metsähovi
  (Finland) in the period 1979-1982 have revealed about a dozen
  radiation sources, microwave limb sources (MW LS), located up to 50
  000 km above the optical limb of the Sun (in normal conditions the
  sources for microwave emission are locate 2 000 - 4 000 km above the
  photosphere). It could be established that MW LS showed up after
  the occurrence of two ribbon flares situated close to the limb of
  the visible hemisphere or that they have been connected to flares
  occuring behind the limb, which was documented by the appearance of
  H<SUB>α</SUB> post flare loop systems. The life time of the MW LS was
  typically about 3 hours and they have been correlated to long decay
  events (LDE) in X-rays. In one case the active region where the MW LS
  appeared was also tracked at Metsähovi and a typical gradual rise and
  fall event was recorded. It is proposed that the MW LS are of thermal
  origin and that they originate from condensed flaring loops appearing
  at successive higher altitudes.

---------------------------------------------------------
Title: The Two Ribbon Flare of May 14, 1981
Authors: Vrsnak, B.; Ruzdjak, V.; Zlobec, P.
1986HvaOB..10...17V    Altcode:
  The flare behaviour at radio waves, X-rays and in H-alpha is
  described. The flare geometry is discussed and compared with the model
  of Heyvaerts et al. (1977).

---------------------------------------------------------
Title: Microwave emission from the limb of the Sun: the events of
    September 8, 1980 and May 10, 1981
Authors: Urpo, S.; Terasranta, H.; Ruzdjak, V.; Vrsnak, B.; Rompolt,
   B.; Kren, G.
1985HvaOB...9...25U    Altcode:
  Solar microwave maps at 8 mm performed at the Metsähovi Radio
  Research Station in the period 1978 - 1982 revealed some radiation
  sources located up to 50000 km outside the optical Sun. The authors
  describe two characteristic events which were associated with large
  flares occurring close to the solar limb.

---------------------------------------------------------
Title: Helical prominences III: the prominence of July 29, 1980
Authors: Vrsnak, B.
1985HvaOB...9...61V    Altcode:
  A prominence, observed at Hvar Observatory on July 29, 1980, is
  described and interpreted. The lower limit of the magnetic field
  strength is estimated to 10 G, while lower limits of the total internal
  current and current density are estimated as 10<SUP>11</SUP>A and
  8×10<SUP>-5</SUP>A/m<SUP>2</SUP>, respectively.

---------------------------------------------------------
Title: The oscillating loop prominence of July 17, 1981
Authors: Vrsnak, B.
1984SoPh...94..289V    Altcode:
  Oscillatory motions of a loop prominence observed on July 17, 1981 are
  analysed. The oscillations were mainly horizontal, with a period of 8
  min. Restoring force was a result of magnetic tension, and assuming a
  simplified magnetic field configuration the expression for frequencies
  of oscillations is derived and compared with the observations. Taking
  the observed period, the strength of the magnetic field permeating
  the prominence is estimated as 45 G. Finally, the stability of the
  prominence is discussed.

---------------------------------------------------------
Title: The Flares of May 14 and 16, 1981, August 19, 1981, October
    14, 1983 and the Associated Radio Events
Authors: Ruzdjak, V.; Vrsnak, B.; Kotrc, P.; Merciar, C.; Schober,
   H. J.; Schroll, A.; Urpo, S.; Zlobec, P.
1984HvaOB...8...25R    Altcode:
  Observational data for the flares of May 14 and 16, 1981,
  August 19, 1981 and October 14, 1983 in the optical and
  radio ranges are presented. It seems that the complexity of the
  photospheric-chromospheric aspect and its time evolution is reflected
  in the radio range.

---------------------------------------------------------
Title: The Hellical Prominence of May 26, 1982
Authors: Vrsnak, B.
1984HvaOB...8...13V    Altcode:
  The observation of a prominence with helical structure is described
  and interpreted. Dynamics, stability and the internal structure of
  the prominence are discussed.

---------------------------------------------------------
Title: The Determination of the Reduction Factors for Sunspot
    Observations at the Astronomical Observatory Zagreb
Authors: Kren, G.; Vrsnak, B.; Ruzdjak, V.
1984HvaOB...8....1K    Altcode:
  Sunspot observations performed at the Astronomical Observatory Zagreb
  in the period May 1979 - June 1983 were investigated. The reduction
  factors of the observed Wolf numbers to the international Wolf numbers
  have been obtained. The dependence of the reduction factors on the
  seeing has been analysed.

---------------------------------------------------------
Title: Correlation of noise storm and H-alpha activity for the CONS
    period Sept. 1 - 4, 1980.
Authors: Vršnak, B.; Ruždjak, V.
1983srs..work..315V    Altcode:
  The Ca plage index was found to be highly correlated with the 260
  MHz radio flux. The noise storm enhancement followed the increase in
  the number of major flares with the delay of one day. The noise storm
  behaviour was correlated with the three hour flare index, but not with
  the one hour flare index.

---------------------------------------------------------
Title: Oscillatory motions of prominences
Authors: Vrsnak, B.
1982HvaOB...6..129V    Altcode:
  Oscillatory motions of a loop prominence observed on July 17, 1981
  are discussed. Stability of the loop, origin of the restoring force
  and magnetic field strength are discussed.

---------------------------------------------------------
Title: Correlation of noise storm and Hα activity for the CONS
    period September 1-4, 1980
Authors: Vršnak, B.; Ruždjak, V.
1982srs..work..315V    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: The helical prominence of March 17, 1977
Authors: Vrsnak, B.; Ruzdjak, V.
1982HvaOB...6..123V    Altcode:
  The dynamics of a prominence with helical structure is studied. The
  slow rising motion accompanied by detwisting indicates that mass loss
  probably caused the prominence rising and decrease of the azimuthal
  component of the magnetic field. The radial dependence of current
  density within the prominence cylinder is discussed.

---------------------------------------------------------
Title: Post SMY observations at Hvar Observatory, May-June 1981
Authors: Ruzdjak, V.; Vrsnak, B.; Novak, N.
1981HvaOB...5...41R    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Some internal mass motions in prominences indicated by special
    spectral features.
Authors: Ruzdjak, V.; Vrsnak, B.
1981PAOS....1..191R    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Observations carried out at Hvar Observatory during SMY,
    August 1979 - February 1981
Authors: Ruzdjak, V.; Vrsnak, B.; Novak, N.
1981HvaOB...5...31R    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Internal mass motions in three eruptive prominences
Authors: Vrsnak, B.
1980HvaOB...4...17V    Altcode:
  No abstract at ADS