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Author name code: anzer
ADS astronomy entries on 2022-09-14
author:"Anzer, Ulrich" 

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Title: 3D modelling of magnetic field and plasma structure of entire
    prominences
Authors: Gunár, Stanislav; Anzer, Ulrich; Heinzel, Petr; Mackay,
   Duncan
2018cosp...42E1315G    Altcode:
  The 3D Whole-Prominence Fine Structure (WPFS) model allows us for
  the first time to simulate entire prominences/filaments including
  their numerous fine structures. This model combines a 3D magnetic
  field configuration of an entire prominence obtained from non-linear
  force-free field simulations, with a detailed description of the
  prominence plasma. The plasma is located in magnetic dips in hydrostatic
  equilibrium and is distributed along hundreds of fine structures
  within the 3D magnetic model. The prominence plasma has realistic
  density and temperature distributions including the prominence-corona
  transition region. This allows us to produce synthetic H-alpha images
  of simulated prominences both in emission on the solar limb and in
  absorption against the solar disk (viewed as filaments) using a single
  model.Such 3D WPFS model provides us with consistent information about
  the prominence magnetic field configuration, prominence fine structure
  plasma and its radiative output. Moreover, we are able to follow the
  evolution of modeled prominences caused by changes of the underlying
  photospheric magnetic flux distribution. Thanks to these capabilities we
  can study links between the photospheric flux distribution, prominence
  magnetic field configuration, distribution and composition of the
  prominence plasma and its observable signatures. These relationships
  are important for interpretation of the observed imaging and
  spectral/spectropolarimetric data and for inference of the properties
  of the prominence magnetic field.

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Title: Plasma physical parameters of a prominence embedded in the
    core of a Coronal Mass Ejection
Authors: Bemporad, Alessandro; Anzer, Ulrich; Heinzel, Petr; Jejcic,
   Sonja; Susino, Roberto
2018cosp...42E.267B    Altcode:
  We determine the plasma physical parameters of an erupting prominence
  embedded in the core of a CME, combininging visible light coronagraphic
  images from SOHO/LASCO with UV spectra acquired by SOHO/UVCS. Strong
  UV emissions were detected in the hydrogen Lyman-α and Lyman-β
  lines and C III line. Visible light and UV intensities have been used
  to estimate the projected thickness and velocity of the prominence,
  together with the effective plasma temperature, microturbolent velocity,
  and column density. These parameters have been used to constrain
  1D NLTE modeling of the erupting plasma, taking into account the
  effects of large flow velocities (Doppler dimming). Roughly one-half
  of considered points in the prominence body show a non-negligible
  Lyman-α optical thickness. Comparison between the calculated and the
  measured intensities of the two Lyman lines was also used to derive the
  geometrical filling factor. Results show that the erupting prominence
  plasma is relatively hot, with a low electron density, a wide range of
  effective thicknesses, a rather narrow range of radial flow velocities,
  and a microturbulence of about 25 km/s. This analysis provides a basis
  for future diagnostics of prominences using the METIS coronagraph on
  board the Solar Orbiter mission.

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Title: Hot Erupting Prominences in Cores of Cme's
Authors: Heinzel, Petr; Bemporad, Alessandro; Anzer, Ulrich; Jejcic,
   Sonja; Susino, Roberto; Dzifcakova, Elena
2018cosp...42E1421H    Altcode:
  Coronal mass ejections (CME) associated with prominence eruptions
  exhibit relatively coolmaterial in their cores. Such prominence
  plasmas were frequently detected in various spectrallines by SOHO/UVCS
  coronagraph and in the visible light by SOHO/LASCO as well as bySTEREO
  coronagraphs. UVCS provided excellent spectra of CME-core prominences
  and anextended catalogue of these data is available. We will present
  recent results of a hot prominence diagnostics using the hydrogen Lyman
  lines and the CIII line . The erupting prominence parameters are further
  constrained by the visible light observations from LASCO-C2. A novel
  non-LTE modeling based on such observations will be presented and we
  will highlight the diagnostic potential of the UV and visible light for
  future space coronagraphs like Metis on board the ESA Solar Orbiter
  mission. The plasma parameters of such hot prominences are compared
  with those obtained from numerical MHD simulations of erupting flux
  ropes surrounded by CMEs. Finally, we will also mention synergies with
  stellar analogues.

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Title: Can 3D whole-prominence fine structure models be used for
    assessment of the prominence plasma mass and distribution prior to
    the onset of CMEs?
Authors: Gunár, Stanislav; Schmieder, Brigitte; Aulanier, Guillaume;
   Anzer, Ulrich; Heinzel, Petr; Mackay, Duncan; Dudik, Jaroslav
2018cosp...42E1316G    Altcode:
  Two complex 3D models of entire prominences including their numerous
  fine structures were recently developed. The first 3D Whole-Prominence
  Fine Structure (WPFS) model was developed by Gunár and Mackay. The
  second 3D WPFS model was put forward by Gunár, Aulanier, Dudík,
  Heinzel, and Schmieder. These 3D prominence models combine simulations
  of the 3D magnetic field configuration of an entire prominence with a
  detailed description of the prominence plasma. The plasma is located
  in magnetic dips in hydrostatic equilibrium and is distributed
  along hundreds of fine structures. The assumed prominence plasma
  has realistic density and temperature distributions including the
  prominence-corona transition region.These 3D WPFS models allow us
  to study the distribution and the mass of the prominence plasma
  contained in prominence magnetic field configurations. These can
  be crucial during the onset and early evolution of CMEs. Moreover,
  prominence plasma represents a bulk of the material ejected by CMEs
  into the interplanetary space. Here, we investigate the potential of
  using the 3D WPFS models for assessment of the role the prominence
  plasma plays in the initiation and evolution of CMEs.

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Title: Quiescent Prominences in the Era of ALMA. II. Kinetic
    Temperature Diagnostics
Authors: Gunár, Stanislav; Heinzel, Petr; Anzer, Ulrich; Mackay,
   Duncan H.
2018ApJ...853...21G    Altcode:
  We provide the theoretical background for diagnostics of the thermal
  properties of solar prominences observed by the Atacama Large
  Millimeter/submillimeter Array (ALMA). To do this, we employ the 3D
  Whole-Prominence Fine Structure (WPFS) model that produces synthetic
  ALMA-like observations of a complex simulated prominence. We use
  synthetic observations derived at two different submillimeter/millimeter
  (SMM) wavelengths—one at a wavelength at which the simulated
  prominence is completely optically thin and another at a wavelength at
  which a significant portion of the simulated prominence is optically
  thick—as if these were the actual ALMA observations. This allows
  us to develop a technique for an analysis of the prominence plasma
  thermal properties from such a pair of simultaneous high-resolution ALMA
  observations. The 3D WPFS model also provides detailed information about
  the distribution of the kinetic temperature and the optical thickness
  along any line of sight. We can thus assess whether the measure of the
  kinetic temperature derived from observations accurately represents
  the actual kinetic temperature properties of the observed plasma. We
  demonstrate here that in a given pixel the optical thickness at the
  wavelength at which the prominence plasma is optically thick needs
  to be above unity or even larger to achieve a sufficient accuracy of
  the derived information about the kinetic temperature of the analyzed
  plasma. Information about the optical thickness cannot be directly
  discerned from observations at the SMM wavelengths alone. However,
  we show that a criterion that can identify those pixels in which
  the derived kinetic temperature values correspond well to the actual
  thermal properties in which the observed prominence can be established.

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Title: Hot prominence detected in the core of a coronal mass
    ejection. II. Analysis of the C III line detected by SOHO/UVCS
Authors: Jejčič, S.; Susino, R.; Heinzel, P.; Dzifčáková, E.;
   Bemporad, A.; Anzer, U.
2017A&A...607A..80J    Altcode:
  Context. We study the physics of erupting prominences in the core
  of coronal mass ejections (CMEs) and present a continuation of a
  previous analysis. <BR /> Aims: We determine the kinetic temperature
  and microturbulent velocity of an erupting prominence embedded in the
  core of a CME that occurred on August 2, 2000 using the Ultraviolet
  Coronagraph and Spectrometer observations (UVCS) on board the Solar
  and Heliospheric Observatory (SOHO) simultaneously in the hydrogen
  Lα and C III lines. We develop the non-LTE (departures from the local
  thermodynamic equilibrium - LTE) spectral diagnostics based on Lα and
  Lβ measured integrated intensities to derive other physical quantities
  of the hot erupting prominence. Based on this, we synthesize the C
  III line intensity to compare it with observations. <BR /> Methods:
  Our method is based on non-LTE modeling of eruptive prominences. We
  used a general non-LTE radiative-transfer code only for optically thin
  prominence points because optically thick points do not allow the
  direct determination of the kinetic temperature and microturbulence
  from the line profiles. The input parameters of the code were the
  kinetic temperature and microturbulent velocity derived from the Lα
  and C III line widths, as well as the integrated intensity of the Lα
  and Lβ lines. The code runs in three loops to compute the radial flow
  velocity, electron density, and effective thickness as the best fit
  to the Lα and Lβ integrated intensities within the accuracy defined
  by the absolute radiometric calibration of UVCS data. <BR /> Results:
  We analyzed 39 observational points along the whole erupting prominence
  because for these points we found a solution for the kinetic temperature
  and microturbulent velocity. For these points we ran the non-LTE code to
  determine best-fit models. All models with τ<SUB>0</SUB>(Lα) ≤ 0.3
  and τ<SUB>0</SUB>(C III) ≤ 0.3 were analyzed further, for which we
  computed the integrated intensity of the C III line using a two-level
  atom. The best agreement between computed and observed integrated
  intensity led to 30 optically thin points along the prominence. The
  results are presented as histograms of the kinetic temperature,
  microturbulent velocity, effective thickness, radial flow velocity,
  electron density, and gas pressure. We also show the relation between
  the microturbulence and kinetic temperature together with a scatter plot
  of computed versus observed C III integrated intensities and the ratio
  of the computed to observed C III integrated intensities versus kinetic
  temperature. <BR /> Conclusions: The erupting prominence embedded in
  the CME is relatively hot with a low electron density, a wide range of
  effective thicknesses, a rather narrow range of radial flow velocities,
  and a microturbulence of about 25 km s<SUP>-1</SUP>. This analysis shows
  a disagreement between observed and synthetic intensities of the C III
  line, the reason for which most probably is that photoionization is
  neglected in calculations of the ionization equilibrium. Alternatively,
  the disagreement might be due to non-equilibrium processes.

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Title: Quiescent Prominences in the Era of ALMA: Simulated
    Observations Using the 3D Whole-prominence Fine Structure Model
Authors: Gunár, Stanislav; Heinzel, Petr; Mackay, Duncan H.; Anzer,
   Ulrich
2016ApJ...833..141G    Altcode:
  We use the detailed 3D whole-prominence fine structure model to
  produce the first simulated high-resolution ALMA observations
  of a modeled quiescent solar prominence. The maps of synthetic
  brightness temperature and optical thickness shown in the present
  paper are produced using a visualization method for synthesis of the
  submillimeter/millimeter radio continua. We have obtained the simulated
  observations of both the prominence at the limb and the filament
  on the disk at wavelengths covering a broad range that encompasses
  the full potential of ALMA. We demonstrate here extent to which the
  small-scale and large-scale prominence and filament structures will be
  visible in the ALMA observations spanning both the optically thin and
  thick regimes. We analyze the relationship between the brightness and
  kinetic temperature of the prominence plasma. We also illustrate the
  opportunities ALMA will provide for studying the thermal structure
  of the prominence plasma from the cores of the cool prominence fine
  structure to the prominence-corona transition region. In addition, we
  show that detailed 3D modeling of entire prominences with their numerous
  fine structures will be important for the correct interpretation of
  future ALMA observations of prominences.

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Title: Hot prominence detected in the core of a coronal mass ejection:
    Analysis of SOHO/UVCS Lα and SOHO/LASCO visible-light observations
Authors: Heinzel, P.; Susino, R.; Jejčič, S.; Bemporad, A.; Anzer, U.
2016A&A...589A.128H    Altcode:
  Context. The paper deals with the physics of erupting prominences in
  the core of coronal mass ejections (CME). <BR /> Aims: We determine the
  physical parameters of an erupting prominence embedded in the core of a
  CME using SOHO/UVCS hydrogen Lα and Lβ lines and SOHO/LASCO visible
  light observations. In particular we analyze the CME event observed
  on August 2, 2000. We develop the non-LTE (NLTE; I.e. considering
  departures from the local thermodynamic equilibrium - LTE) spectral
  diagnostics based on Lα and visible light observations. <BR /> Methods:
  Our method is based on 1D NLTE modeling of eruptive prominences and
  takes into account the effect of large flow velocities, which reach
  up to 300 km s<SUP>-1</SUP> for the studied event (the so-called
  Doppler dimming). The NLTE radiative-transfer method can be used
  for both optically thin and thick prominence structures. We combine
  spectroscopic UVCS observations of an erupting prominence in the core
  of a CME with visible light images from LASCO-C2 in order to derive the
  geometrical parameters like projected thickness and velocity, together
  with the effective temperature and column density of electrons. These
  are then used to constrain our NLTE radiative transfer modeling which
  provides the kinetic temperature, microturbulent velocity, gas pressure,
  ionization degree, the line opacities, and the prominence effective
  thickness (geometrical filling factor). <BR /> Results: Analysis was
  made for 69 observational points (spatial pixels) inside the whole
  erupting prominence. Roughly one-half of them show a non-negligible Lα
  optical thickness for flow velocity 300 km s<SUP>-1</SUP> and about
  one-third for flow velocity 150 km s<SUP>-1</SUP>. All pixels with
  Lατ<SUB>0</SUB> ≤ 0.3 have been considered for further analysis,
  which is presented in the form of statistical distributions (histograms)
  of various physical quantities such as the kinetic temperature, gas
  pressure, and electron density for two representative flow velocities
  (150 and 300 km s<SUP>-1</SUP>) and non-zero microturbulence. For
  two pixels co-temporal LASCO visible-light data are also available,
  which further constrains the diagnostics of the electron density and
  effective thickness. Detailed NLTE modeling is presented for various
  sets of input parameters. <BR /> Conclusions: The studied CME event
  shows that the erupting prominence expands to large volumes, meaning
  that it is a low-pressure structure with low electron densities and
  high temperatures. This analysis provides a basis for future diagnostics
  using the METIS coronagraph on board the Solar Orbiter mission.

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Title: Is it Possible to Use the Green Coronal Line Instead of X rays
    to Cancel an Effect of the Coronal Emissivity Deficit in Estimation of
    the Prominence Total Mass from Decrease of the EUV-corona Intensities?
Authors: Schwartz, P.; Heinzel, P.; Jejčič, S.; Rybák, J.; Kotrč,
   P.; Fárník, F.; Kupryakov, Yu. A.; Deluca, E. E.; Golub, L.; Jibben,
   P. R.; Anzer, U.; Tlatov, A. G. .; Guseva, S. A.
2016ASPC..504...89S    Altcode:
  Total masses of six quiescent prominences observed from April through
  June 2011 were estimated using multi-spectral observations (in EUV,
  X-rays, Hα, and Ca &lt;small&gt;II&lt;/small&gt; H). The method for
  the total mass estimation is based on the fact that the intensity
  of the EUV solar corona at wavelengths below 912 Å is reduced at a
  prominence by the absorption in resonance continua (photoionisation)
  of hydrogen and possibly by helium and subsequently an amount of
  absorbed radiation is proportional to the column density of hydrogen
  and helium plasma. Moreover, the deficit of the coronal emissivity in
  volume occupied by the cool prominence plasma also contributes to the
  intensity decrease. The observations in X-rays which are not absorbed
  by the prominence plasma, allow us to separate these two mechanisms
  from each other. The X-ray observations of XRT onboard the Hinode
  satellite made with the Al-mesh focal filter were used because the
  X-ray coronal radiation formed in plasma of temperatures of the order
  of 10<SUP>6</SUP> K was registered and EUV spectral lines occurring in
  the 193, 211 and 335 Å channels of the Atmospheric Imaging Assembly
  of the Solar Dynamics Observatory satellite are also formed at such
  temperatures. Unfortunately, the Al-mesh filter has a secondary peak
  of the transmittance at around 171 Å which causes a contribution
  from the EUV corona to the measured data of up to 11 % in the quiet
  corona. Thus, absorption in prominence plasma influences XRT X-ray
  data when using the Al-mesh filter. On the other hand, other X-ray XRT
  filters are more sensitive to plasma of much higher temperatures (log
  T of the order of 7), thus observations using these filters cannot
  be used together with the AIA observations in the method for mass
  estimations. This problem could be solved using observations in the
  green coronal line instead of X-rays. Absorption of the green coronal
  line by a prominence plasma is negligible and this line is formed at
  temperatures of the order of 10<SUP>6</SUP> K. We compare values of
  the total mass of the prominence observed on 20 October 2012 on the
  SE limb estimated when using XRT X-ray observations and observations
  in the green coronal line obtained at Kislovodsk Mountain Astronomical
  Station of the Pulkovo observatory (Russia).

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Title: Observed IRIS Profiles of the h and k Doublet of Mg II and
    Comparison with Profiles from Quiescent Prominence NLTE Models
Authors: Vial, Jean-Claude; Pelouze, Gabriel; Heinzel, Petr; Kleint,
   Lucia; Anzer, Ulrich
2016SoPh..291...67V    Altcode: 2015SoPh..tmp..173V
  With the launch of the Interface Region Imaging Spectrograph (IRIS)
  mission, it is now possible to obtain high-resolution solar prominence
  spectra and to begin to distinguish the contributions of the many
  (apparent or not) threads that structure prominences. We aim at
  comparing unique observations obtained in the Mg II h and k lines of a
  polar crown prominence with the radiative outputs from one-dimensional
  models built with non-local-thermodynamic equilibrium codes (Heinzel et
  al.Astron. Astrophys.564, A132, 2014). We characterize the profiles
  obtained through thorough calibration procedures, with attention
  paid to the absolute values, full-width at half-maximum, and the
  ratio of k to h intensities. We also show that at the top of some
  structures, line-of-sight velocities of about 9 kms−<SUP>1</SUP> can
  be detected. We find a range of static, low-pressure, low-thickness,
  low-temperature models that could fit k or h observed values, but that
  cannot satisfy the low observed k/h ratio. We investigate whether these
  low values might be explained by the inclusion of horizontal flows in
  small-scale threads. These flows are also necessary in another class
  of models, where the pressure is kept low but thickness and temperature
  are increased up to the observed thickness and up to 15 000 K.

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Title: High-resolution fine-structure synthetic imaging of an entire
    prominence using 3D whole-prominence fine structure modelling
Authors: Gunar, Stanislav; Mackay, Duncan; Heinzel, Petr; Anzer, Ulrich
2015IAUGA..2251323G    Altcode:
  The newly developed 3D whole-prominence fine structure (WPFS)
  model (Gunár &amp; Mackay 2015) allows us for the first time to
  simulate entire prominences/filaments including their numerous fine
  structures. This model combines a 3D magnetic field configuration of an
  entire prominence obtained from non-linear force-free field simulations,
  with a detailed description of the prominence plasma. The plasma is
  located in magnetic dips in hydrostatic equilibrium and is distributed
  along hundreds of fine structures within the 3D magnetic model. The
  prominence plasma has realistic density and temperature distributions
  including the prominence-corona transition region.To produce the
  high-resolution synthetic H-alpha images of the WPFS model we use
  a novel fast approximate radiative transfer visualization technique
  (Heinzel et al. 2015). This allows us for the first time to produce
  images of the prominences in emission on the solar limb and filaments in
  absorption against the solar disk using a single model. The prominence
  plasma and magnetic field are described in the WPFS model on scales
  that allow us to produce synthetic images with resolution matching that
  of the state-of-the-art observations, or indeed that of the upcoming
  solar observatories, such as DKIST or Solar-C. Moreover, to complement
  the prominence/filament synthetic images we have consistent information
  about the magnetic field and plasma parameters everywhere in the modeled
  prominences. This allows us to investigate the apparent puzzling nature
  of the observed prominence and filament fine structures. We can also
  study the connections between the local configuration of the magnetic
  field and the observable structure of the finest prominence/filament
  features. In addition, we are able to investigate the prominence
  evolution. We can consistently study the influence of the varying
  photospheric flux distribution on the prominence magnetic field
  configuration and its effect on the observable prominence plasma.

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Title: Fast approximate radiative transfer method for visualizing
    the fine structure of prominences in the hydrogen Hα line
Authors: Heinzel, P.; Gunár, S.; Anzer, U.
2015A&A...579A..16H    Altcode:
  <BR /> Aims: We present a novel approximate radiative transfer method
  developed to visualize 3D whole-prominence models with multiple fine
  structures using the hydrogen Hα spectral line. <BR /> Methods: This
  method employs a fast line-of-sight synthesis of the Hα line profiles
  through the whole 3D prominence volume and realistically reflects the
  basic properties of the Hα line formation in the cool and low-density
  prominence medium. The method can be applied both to prominences seen
  above the limb and filaments seen against the disk. <BR /> Results:
  We provide recipes for the use of this method for visualizing the
  prominence or filament models that have multiple fine structures. We
  also perform tests of the method that demonstrate its accuracy
  under prominence conditions. <BR /> Conclusions: We demonstrate that
  this fast approximate radiative transfer method provides realistic
  synthetic Hα intensities useful for a reliable visualization of
  prominences and filaments. Such synthetic high-resolution images of
  modeled prominences/filaments can be used for a direct comparison with
  high-resolution observations.

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Title: Prominence Visibility in Hinode/XRT Images
Authors: Schwartz, P.; Jejčič, S.; Heinzel, P.; Anzer, U.; Jibben,
   P. R.
2015ApJ...807...97S    Altcode: 2015arXiv150606078S
  In this paper we study the soft X-ray (SXR) signatures of one
  particular prominence. The X-ray observations used here were made by the
  Hinode/X-Ray Telescope instrument using two different filters. Both of
  them have a pronounced peak of the response function around 10 Å. One
  of them has a secondary smaller peak around 170 Å, which leads to a
  contamination of SXR images. The observed darkening in both of these
  filters has a very large vertical extension. The position and shape of
  the darkening correspond nicely with the prominence structure seen in
  SDO/AIA images. First, we have investigated the possibility that the
  darkening is caused by X-ray absorption. However, detailed calculations
  of the optical thickness in this spectral range show clearly that
  this effect is completely negligible. Therefore, the alternative is
  the presence of an extended region with a large emissivity deficit,
  which can be caused by the presence of cool prominence plasmas within
  an otherwise hot corona. To reproduce the observed darkening, one needs
  a very large extension along the line of sight of the region amounting
  to around 10<SUP>5</SUP> km. We interpret this region as the prominence
  spine, which is also consistent with SDO/AIA observations in EUV.

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Title: On the formation of Mg ii h and k lines in solar prominences
Authors: Heinzel, P.; Vial, J. -C.; Anzer, U.
2014A&A...564A.132H    Altcode:
  <BR /> Aims: With the recent launch of the IRIS mission, it has become
  urgent to develop the spectral diagnostics using the Mg ii resonance
  h and k lines. In this paper, we aim to demonstrate the behavior of
  these lines under various prominence conditions. Our results serve
  as a basis for analysis of new IRIS data and for more sophisticated
  prominence modeling. <BR /> Methods: For this exploratory work,
  we use a canonical 1D prominence-slab model, which is isobaric
  and may have three different temperature structures: isothermal,
  PCTR-like (prominence-corona transition region), and consistent with
  the radiative equilibrium. The slabs are illuminated by a realistic
  incident solar radiation obtained from the UV observations. A five-level
  plus continuum Mg ii model atom is used to solve the full NLTE problem
  of the radiative transfer. We use the numerical code based on the ALI
  techniques and apply the partial frequency redistribution for both
  Mg ii resonance lines. We also use the velocity-dependent boundary
  conditions to study the effect of Doppler dimming in the case of
  moving prominences. Finally, the relaxation technique is used to
  compute a grid of models in radiative equilibrium. <BR /> Results:
  We computed the Mg ii h and k line profiles that are emergent from
  prominence-slab models and show their dependence on kinetic temperature,
  gas pressure, geometrical extension, and microturbulent velocity. By
  increasing the line opacity, significant departures from the complete
  frequency redistribution take place in the line wings. Models with a
  PCTR temperature structure show that Mg ii becomes ionized to Mg iii
  in the temperature range between roughly 15 000 and 30 000 K. Doppler
  dimming is significant for Mg ii resonance lines. At the velocity 300
  km s<SUP>-1</SUP>, the line intensity decreases to about 20% of the
  value for static prominences. Finally, we demonstrate the role of Mg
  ii h and k radiation losses on the prominence energy balance. Their
  dominant role is at lower pressures, while the losses due to hydrogen
  and Ca ii dominate at higher pressures.

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Title: A comparison between observed IRIS profiles of the h &amp;
    k doublet of Mg II and profiles from quiescent prominence NLTE models
Authors: Vial, Jean-Claude; Anzer, Ulrich; Heinzel, Petr; Kleint, Lucia
2014cosp...40E3515V    Altcode:
  With the advent of IRIS, it is now possible to investigate the cool core
  of prominences through the detailed profiles of the Mg II resonance
  lines with an unprecedented spatial resolution of 0.33 arcsecond. The
  slit-jaw camera also allows to record the temporal evolution of the
  prominence fine structure. We present IRIS observations of quiescent
  prominence profiles that we analyse in terms of reversal (if any),
  width, k/h line ratio, prominence/ quiet Sun line ratio. Comparing these
  parameters with the results of NLTE modelling (see Heinzel et al. 2014),
  we can derive thermodynamic parameters of the cool prominence plasma,
  along with the (line-of-sight) velocities and mass flows.

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Title: Puzzling nature of the fine structure of quiescent prominences
    and filaments
Authors: Gunár, Stanislav; Heinzel, Petr; Anzer, Ulrich; Mackay,
   Duncan H.
2013JPhCS.440a2035G    Altcode:
  Even after more than 160 years of observations and modelling of solar
  prominences their true nature contains many open questions. In this
  work we argue that current 2D prominence fine structure models can
  help us to understand the puzzling connection between quasi-vertical
  fine structures often seen in quiescent prominences observed on the
  solar limb and horizontally aligned dark fibrils representing the fine
  structures of prominences observed in absorption against the solar disk
  (filaments).

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Title: Non-linear force-free magnetic dip models of quiescent
    prominence fine structures
Authors: Gunár, S.; Mackay, D. H.; Anzer, U.; Heinzel, P.
2013A&A...551A...3G    Altcode:
  <BR /> Aims: We use 3D non-linear force-free magnetic field modeling
  of prominence/filament magnetic fields to develop the first 2D models
  of individual prominence fine structures based on the 3D configuration
  of the magnetic field of the whole prominence. <BR /> Methods: We use
  an iterative technique to fill the magnetic dips produced by the 3D
  modeling with realistic prominence plasma in hydrostatic equilibrium
  and with a temperature structure that contains the prominence-corona
  transition region. With this well-defined plasma structure the radiative
  transfer can be treated in detail in 2D and the resulting synthetic
  emission can be compared with prominence/filament observations. <BR
  /> Results: Newly developed non-linear force-free magnetic dip models
  are able to produce synthetic hydrogen Lyman spectra in a qualitative
  agreement with a range of quiescent prominence observations. Moreover,
  the plasma structure of these models agrees with the gravity induced
  prominence fine structure models which have already been shown to
  produce synthetic spectra in good qualitative agreement with several
  observed prominences. <BR /> Conclusions: We describe in detail the
  iterative technique which can be used to produce realistic plasma
  models of prominence fine structures located in prominence magnetic
  field configurations containing dips, obtained using any kind of
  magnetic field modeling.

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Title: Velocity Vector, Ionization Degree, and Temperature of
    Prominence Fine Structures Observed by Hinode/SOT
Authors: Schmieder, B.; Mein, P.; Chandra, R.; Molodij, G.; Heinzel,
   P.; Berlicki, A.; Schwartz, P.; Fárník, F.; Labrosse, N.; Anzer,
   U.; Watanabe, T.
2012ASPC..454..107S    Altcode:
  Prominences have been successfully observed by Hinode in April 2007
  exhibiting a strong dynamics of their fine structures. The dynamics
  of a prominence is a challenge to understand the formation of cool
  prominence plasma embedded in the hot corona. Combining simultaneous
  observations obtained in Hα with Hinode/SOT and the MSDP spectrograph
  operating at the Meudon solar tower, velocity vectors have been
  derived. The Doppler-shifts of bright threads are of the same order
  as the velocities measured perpendicular to the line of sight. This
  suggests that the vertical structures of the prominence could be a pile
  up of dips in magnetic field lines viewed in 3D. Using Hα, Hinode/XRT
  and TRACE data, the hydrogen ionization degree has been determined to
  be 0.5-0.8, and the optical thickness in Hα between 0.2 and 1.3. The
  Extreme Ultraviolet Imaging Spectrometer (EIS) on Hinode produced images
  of the prominence in 11 selected lines with formation temperatures
  between log(T) = 4.7 and log(T) = 6.1. We comment on the absorption,
  emissivity blocking and emission involved for interpreting the different
  structures of the prominence in terms of the temperature and density.

---------------------------------------------------------
Title: Mass of Solar Prominences Estimated from Multi-Wavelength Data
Authors: Schwartz, P.; Fárník, F.; Heinzel, P.; Kotrč, P.; Anzer, U.
2012ASPC..454..117S    Altcode:
  The mass of selected prominences was estimated using their
  multi-wavelength observations: in Hα by the HSFA2 spectrograph of
  the Ondřejov observatory, in EUV by SoHO/EIT and in the soft X-rays
  by Hinode XRT. The results are compared with values estimated by
  other authors.

---------------------------------------------------------
Title: Mass Loading of Quiescent Prominences
Authors: Schwartz, P.; Heinzel, 2. P.; Kotrč, P.; Anzer, U.;
   Kupryakov, Y.; DeLuca, E.
2012ASPC..456...73S    Altcode:
  From April through June 2011 a multi-spectral observing campaign of
  quiescent prominences was made. Observations were carried out in EUV
  by SDO/AIA, in soft X-rays by XRT on Hinode and in Hα by horizontal
  spectrographs of the Ondrřejov observatory. In this work the masses of
  selected prominences, observed on May 18 and April 19, were determined
  in order to test the method and our semi-automatic computer code.

---------------------------------------------------------
Title: Radiative equilibrium in solar prominences reconsidered
Authors: Heinzel, P.; Anzer, U.
2012A&A...539A..49H    Altcode:
  <BR /> Aims: We reconsider the question which kinetic temperatures
  can lead to prominence configurations that are in radiative
  equilibrium. We compare these temperatures to those from other
  calculations. <BR /> Methods: For this purpose we solved the full
  non-LTE radiative-transfer problem for a gas consisting of hydrogen,
  helium and calcium. We used simple isobaric 1D slabs and began with
  isothermal models. Then we solved the radiative-relaxation problem
  and determined the radiative-equilibrium conditions within the
  whole slab. <BR /> Results: By adding the calcium radiative losses,
  we found that these equilibrium temperatures are considerably lower
  than those obtained for a pure hydrogen gas. This is because the newly
  calculated CaII line losses appear to play a significant role in the
  energy balance, similar to chromospheric conditions. The equilibrium
  temperatures obtained span the range between 4400-9500 K, depending
  on the gas pressure and slab thickness.

---------------------------------------------------------
Title: Synthetic differential emission measure curves of prominence
    fine structures. II. The SoHO/SUMER prominence of 8 June 2004
Authors: Gunár, S.; Parenti, S.; Anzer, U.; Heinzel, P.; Vial, J. -C.
2011A&A...535A.122G    Altcode:
  <BR /> Aims: This study is the first attempt to combine the prominence
  observations in Lyman, UV, and EUV lines with the determination of the
  prominence differential emission measure derived using two different
  techniques, one based on the inversion of the observed UV and EUV lines
  and the other employing 2D non-LTE prominence fine-structure modeling
  of the Lyman spectra. <BR /> Methods: We use a trial-and-error method
  to derive the 2D multi-thread prominence fine-structure model producing
  synthetic Lyman spectra in good agreement with the observations. We then
  employ a numerical method to perform the forward determination of the
  DEM from 2D multi-thread models and compare the synthetic DEM curves
  with those derived from observations using inversion techniques. <BR
  /> Results: A set of available observations of the June 8, 2004
  prominence allows us to determine the range of input parameters, which
  contains models producing synthetic Lyman spectra in good agreement
  with the observations. We select three models, which represent this
  parametric-space area well and compute the synthetic DEM curves for
  multi-thread realizations of these models. The synthetic DEM curves
  of selected models are in good agreement with the DEM curves derived
  from the observations. <BR /> Conclusions: We show that the evaluation
  of the prominence fine-structure DEM complements the analysis of the
  prominence hydrogen Lyman spectra and that its combination with the
  detailed radiative-transfer modeling of prominence fine structures
  provides a useful tool for investigating the prominence temperature
  structure from the cool core to the prominence-corona transition region.

---------------------------------------------------------
Title: Synthetic differential emission measure curves of prominence
    fine structures
Authors: Gunár, S.; Heinzel, P.; Anzer, U.
2011A&A...528A..47G    Altcode:
  <BR /> Aims: We use 2D single and multi-thread prominence fine-structure
  models to obtain the synthetic DEM curves. These are then compared
  with the DEM curves derived from observations. <BR /> Methods: We use
  the temperature and electron density structure resulting from the
  2D models and numerically compute the average synthetic DEM curves
  for different orientations of the threads with respect to the line of
  sight. <BR /> Results: We show that the synthetic DEM curves obtained
  by 2D modelling are similar to the DEM curves derived from observations
  of quiescent prominences. <BR /> Conclusions: The DEM curves derived
  from observations, which are most reliable above temperatures of 20
  000 K, can be extended towards cool prominence-core temperatures by
  supplementing them with synthetic DEM values obtained by modelling
  hydrogen Lyman spectra originating mainly at temperatures below 20 000
  K. On the other hand, the observed DEM can constrain the temperature
  structure of the prominence fine structures above the formation
  temperatures of the Lyman spectrum.

---------------------------------------------------------
Title: Statistical comparison of the observed and synthetic hydrogen
    Lyman line profiles in solar prominences
Authors: Gunár, S.; Schwartz, P.; Schmieder, B.; Heinzel, P.;
   Anzer, U.
2010A&A...514A..43G    Altcode:
  <BR /> Aims: We analyse a unique set of prominence SOHO/SUMER
  Lyman spectra by comparing it with synthetic spectra obtained by 2D
  multi-thread prominence fine-structure models. <BR /> Methods: We
  employed a novel statistical approach to the analysis of the observed
  and synthetic Lyman spectra. We compared the statistical distributions
  of the line properties of the observed and synthetic Lyman spectra using
  a set of four statistical criteria. <BR /> Results: We demonstrate
  the very good agreement between the observed Lyman spectra and
  synthetic spectra obtained by modelling. <BR /> Conclusions: Our set
  of statistical criteria is well-suited to analyses of the prominence
  Lyman spectra because of its sensitivity to a number of different
  parameters governing the conditions in the prominence fine structures.

---------------------------------------------------------
Title: How do unresolved motions affect the prominence hydrogen
    Lyman spectrum.
Authors: Gunar, Stanislav; Schwartz, Pavol; Schmieder, Brigitte;
   Heinzel, Petr; Anzer, Ulrich
2010cosp...38.2830G    Altcode: 2010cosp.meet.2830G
  Space-born observations of quiescent prominences in the hydrogen
  Lyman line series provide a considerable amount of information
  about their structure and physical properties. Lyman line series
  thus represents a focus of several detailed studies. However, the
  substantial asymmetries exhibited by considerable number of observed
  Lyman line profiles present a strong indication for the existence of
  hidden fine-structure dynamics. If attributed merely to the Doppler
  shift effect, these asymmetries would correspond to radial velocities
  of the order of 100 km/s. Such high velocities, however, were never
  observed in quiescent prominences. Typical fine-structure velocities are
  of the order of 10 km/s. To tackle this problem, we have modified our
  2D multi-thread prominence models and randomly assigned line-of-sight
  (LOS) velocities of the order of 10 km/s to each thread. The obtained
  synthetic Lyman spectrum exhibits substantial asymme-tries of the line
  profiles comparable with SOHO/SUMER observations. Moreover, our results
  do indicate that the synthetic Lyman-α profiles may exhibit an opposite
  asymmetry to that of the higher Lyman lines. This is consistent with
  observations which often show opposite asym-metries of these lines at
  the same prominence location. We have demonstrated the agreement of
  synthetic and observed spectra not only by comparing asymmetries of
  individual profiles but also by exploiting statistically significant
  sets of the observed and synthetic data. These results represent an
  important step in our understanding of hidden fine-structure dynamics
  of quiescent prominences.

---------------------------------------------------------
Title: Prominence fine structures and corresponding differential
    emission measures
Authors: Gunar, Stanislav; Heinzel, Petr; Anzer, Ulrich
2010cosp...38.2845G    Altcode: 2010cosp.meet.2845G
  We use the temperature and density structure resulting from multi-thread
  prominence fine-structure models (consisting of individual 2D
  vertical threads) to compute the differential emission measures
  (DEM). We derive the DEM at various positions along the length of
  the foremost thread of the multi-thread model and also for various
  angles between the line-of-sight and the magnetic field. We compare
  the calculated DEM values with those obtained by in-versions from
  the observed intensities of the transition-region UV lines. We show
  that the unresolved fine-structuring of quiescent prominences along a
  particular line-of-sight has consid-erable effect on shape of the DEM
  curve due to fracturing of the prominence-corona transition region into
  many thin layers corresponding to individual prominence fine structures.

---------------------------------------------------------
Title: Solar quiescent prominences. Filamentary structure and
    energetics
Authors: Heinzel, P.; Anzer, U.; Gunár, S.
2010MmSAI..81..654H    Altcode:
  We present a first attempt to solve the non-LTE radiative-transfer
  problem within a 2D numerical domain consisting of several randomly
  distributed vertical threads. This represents a starting point
  to simulate mutual radiative interaction between such prominence
  threads. The second part of the paper presents our new results which
  concern the radiative equilibrium in prominences and in their fine
  structure. We show that adding the non-hydrogenic radiative losses
  significantly lowers the central equilibrium temperatures. To match the
  observed temperatures, an additional heating seems to be unavoidable.

---------------------------------------------------------
Title: Global prominence oscillations
Authors: Anzer, U.
2009A&A...497..521A    Altcode:
  Aims: The question of the different oscillation periods for global
  modes of quiescent prominences is discussed. <BR />Methods: Simple 1D
  prominence configurations are used to describe the magnetohydrostatic
  equilibrium and their oscillations for small amplitudes. <BR />Results:
  Three basic modes of oscillations were found and their periods as a
  function of the magnetic field configuration and the assumed geometry
  are given.

---------------------------------------------------------
Title: On Lyman-line asymmetries in quiescent prominences
Authors: Gunár, S.; Heinzel, P.; Anzer, U.; Schmieder, B.
2008A&A...490..307G    Altcode:
  Aims: We study the asymmetries of the synthetic hydrogen Lyman
  lines and the process responsible for their formation. <BR
  />Methods: To obtain the synthetic Lyman line profiles, we use a
  multi-thread prominence fine-structure model consisting of identical
  2D threads. The 2D thread models are in MHS equilibrium, include an
  empirical prominence-corona transition region, and solve consistently
  2D non-LTE radiative transfer. Each thread of the multi-thread model
  has a randomly assigned line-of-sight (LOS) velocity. <BR />Results:
  The synthetic Lyman spectrum obtained by multi-thread modelling
  exhibits substantial asymmetries of the line profiles, even though
  the LOS velocities of individual threads are only of the order of 10
  km s<SUP>-1</SUP>. Moreover, our results indicate that the synthetic
  Lyman-α profiles may exhibit an opposite asymmetry to that of the
  higher Lyman lines. <BR />Conclusions: The presence and behaviour
  of the asymmetrical profiles of the synthetic Lyman lines agree with
  observed profiles acquired by SUMER. <P />Appendix A is only available
  in electronic form at http://www.aanda.org

---------------------------------------------------------
Title: Hinode, TRACE, SOHO, and Ground-based Observations of a
    Quiescent Prominence
Authors: Heinzel, P.; Schmieder, B.; Fárník, F.; Schwartz, P.;
   Labrosse, N.; Kotrč, P.; Anzer, U.; Molodij, G.; Berlicki, A.;
   DeLuca, E. E.; Golub, L.; Watanabe, T.; Berger, T.
2008ApJ...686.1383H    Altcode:
  A quiescent prominence was observed by several instruments on
  2007 April 25. The temporal evolution was recorded in Hα by the
  Hinode SOT, in X-rays by the Hinode XRT, and in the 195 Å channel by
  TRACE. Moreover, ground-based observatories (GBOs) provided calibrated
  Hα intensities. Simultaneous extreme-UV (EUV) data were also taken by
  the Hinode EIS and SOHO SUMER and CDS instruments. Here we have selected
  the SOT Hα image taken at 13:19 UT, which nicely shows the prominence
  fine structure. We compare this image with cotemporaneous ones taken
  by the XRT and TRACE and show the intensity variations along several
  cuts parallel to the solar limb. EIS spectra were obtained about half
  an hour later. Dark prominence structure clearly seen in the TRACE and
  EIS 195 Å images is due to the prominence absorption in H I, He I,
  and He II resonance continua plus the coronal emissivity blocking due
  to the prominence void (cavity). The void clearly visible in the XRT
  images is entirely due to X-ray emissivity blocking. We use TRACE, EIS,
  and XRT data to estimate the amount of absorption and blocking. The
  Hα integrated intensities independently provide us with an estimate of
  the Hα opacity, which is related to the opacity of resonance continua
  as follows from the non-LTE radiative-transfer modeling. However,
  spatial averaging of the Hα and EUV data have quite different natures,
  which must be taken into account when evaluating the true opacities. We
  demonstrate this important effect here for the first time. Finally,
  based on this multiwavelength analysis, we discuss the determination
  of the column densities and the ionization degree of hydrogen in
  the prominence.

---------------------------------------------------------
Title: On Lyman-line Asymmetries in Quiescent Prominences
Authors: Gunár, S.; Heinzel, P.; Anzer, U.; Schmieder, B.
2008ESPM...12.3.18G    Altcode:
  We present a new study of the asymmetries of synthetic hydrogen Lyman
  line profiles and suggest the mechanism of their formation. <P />In
  order to obtain the synthetic Lyman line profiles, we use multi-thread
  prominence fine-structure model consisting of identical vertical
  2D threads. The 2D thread models are in magnetohydrostatic (MHS)
  equilibrium, include an empirical prominence-corona transition
  region (PCTR) and consistently solve the 2D non-LTE radiative
  transfer. Individual threads of the multi-thread fine-structure model
  have a randomly assigned LOS velocities. <P />The synthetic Lyman
  spectrum obtained by our multi-thread modelling exhibits substantial
  asymmetries of the line profiles even thought the LOS velocities
  of individual threads are only of the order of 10 km s-1. Moreover,
  our results show that the synthetic Lyman-? profiles may exhibit an
  opposite asymmetry as compared to higher Lyman lines. These results are
  in agreement with the observed Lyman line profiles from SOHO/SUMER. <P
  />The presence and the behaviour of the asymmetrical profiles of the
  synthetic Lyman spectrum is in agreement with observed profiles taken
  by SUMER.

---------------------------------------------------------
Title: Prominence modelling: from observed emission measures to
    temperature profiles
Authors: Anzer, U.; Heinzel, P.
2008A&A...480..537A    Altcode:
  Aims:We outline the construction of prominence - corona transition
  region models based upon the observations of one particular
  prominence. <BR />Methods: The differential emission measure curves from
  observations were approximated by simple analytical functions. On this
  basis we constructed the temperature curve and calculated the radiative
  losses, the gains by thermal conduction, and some estimates for the
  wave heating. <BR />Results: The temperature curve was calculated in
  the range between 23 000 K and 450 000 K. The resulting transition
  region can be divided into an inner region where the temperature is
  low and the radiative losses are very large, a part with a very steep
  temperature rise from 40 000 K to around 250 000 K over a width of only
  500 km, and an extended high temperature region. Both the conductive
  heating and our estimates for a possible wave cooling/heating peak very
  sharply in the region with the very large temperature gradient. The
  consequences for the energy balance are discussed.

---------------------------------------------------------
Title: Limb Prominences Seen in UV, EUV and SXR
Authors: Heinzel, P.; Fárník, F.; Anzer, U.; Dammasch, I.
2007ASPC..369..279H    Altcode:
  We use SOHO/SUMER, EIT and Yohkoh/SXT prominence observations to study
  the absorption and/or volume blocking of UV, EUV and SXR coronal
  radiation by cool prominence plasma. An example of such a complex
  behaviour is the limb prominence observed on 5 September 1996. The
  SUMER spectrograph has detected two coronal lines, MgX at 625 Å,
  which is absorbed by the hydrogen Lyman continuum and blocked within
  a volume occupied by cool prominence plasma, and FeXII at 1242 Å,
  where the prominence appears dark due to blocking (no absorption at
  this wavelength). A similar behaviour show also the EUV images taken by
  EIT. We find that a darkening similar to that detected in the FeXII line
  is quite well visible also in the SXR images obtained by Yohkoh/SXT. To
  explain this feature, we exclude the absorption by the HeI and HeII
  resonance continua (hydrogen absorption is quite negligible) and suggest
  that it is entirely due to the volume blocking. Based on a quantitative
  analysis of these data, we discuss the physical conditions in cool
  prominences and their coronal environment. Finally, we propose new
  high-resolution EUV and SXR observations of prominences by Solar-B,
  using the EUV imaging spectrometer (EIS) and the X-ray telescope
  (XRT), respectively.

---------------------------------------------------------
Title: Properties of prominence fine-structure threads derived from
    SOHO/SUMER hydrogen Lyman lines
Authors: Gunár, S.; Heinzel, P.; Schmieder, B.; Schwartz, P.;
   Anzer, U.
2007A&A...472..929G    Altcode:
  Context: The SOHO/SUMER observations provide us for the first time with
  the prominence spectra in the Lyman-α line outside the attenuator
  together with the higher members of the hydrogen Lyman series. <BR
  />Aims: We derive the prominence fine-structure thread properties
  by comparing the SOHO/SUMER hydrogen Lyman series observations with
  the synthetic Lyman lines. <BR />Methods: To obtain the synthetic
  profiles of the Lyman lines, we used 2D prominence fine-structure
  thread models with a PCTR and consistently solved the 2D non-LTE
  multilevel radiative transfer. The trial-and-error method was applied
  to find the model with the best agreement between the synthetic Lyman
  line profiles and the observed ones. <BR />Results: The properties of
  the resulting model with the best match of the synthetic and observed
  line profiles are central (minimum) temperature T<SUB>0</SUB> = 7000
  K, maximum column mass in the centre of the thread M<SUB>0</SUB> =
  1.1×10<SUP>-4</SUP> g cm<SUP>-2</SUP>, horizontal field strength in
  the middle of the thread B<SUB>x</SUB>(0) = 6 Gauss and the boundary
  pressure p<SUB>0</SUB> = 0.015 dyn cm<SUP>-2</SUP>. <BR />Conclusions:
  The Lyman line profiles observed by SOHO/SUMER can be better reproduced
  by using multi-thread models consisting of a set of the 2D prominence
  fine-structure threads placed perpendicularly to the line-of-sight,
  rather than with the single-thread model.

---------------------------------------------------------
Title: Is the magnetic field in quiescent prominences force-free?
Authors: Anzer, U.; Heinzel, P.
2007A&A...467.1285A    Altcode:
  Aims:We describe under which conditions the magnetic fields of quiescent
  prominences are force-free and under which gravity plays the dominant
  role. <BR />Methods: The existing observational determinations of the
  magnetic field are summarised and the calculation of the plasma β
  is outlined. We derive the dependence of β on the prominence weight
  and the field strength. <BR />Results: We show that in many cases of
  well-developed quiescent prominences the field can deviate substantially
  from the force-free situation and gravity fully determines the structure
  of the magnetic dips.

---------------------------------------------------------
Title: Prominence Parameters from 2D Modeling of Lyman Lines Measured
    with SUMER
Authors: Gunár, S.; Heinzel, P.; Schmieder, B.; Anzer, U.
2007ASPC..368..317G    Altcode:
  We present SOHO/SUMER observations of a solar prominence in the hydrogen
  Lyman series lines and compare the line profiles with the synthetic
  ones obtained using our 2D prominence modeling. The observations
  contain the Ly-β, Ly-γ, and Ly-δ lines on 25 May 2005. <P />In
  order to derive the prominence parameters we used our 2D fine structure
  models of vertical threads in magnetohydrostatic (MHS) equilibrium. By
  varying the input model parameters (central temperature, boundary
  pressure, magnetic field, central column mass and turbulent velocity)
  we obtained a model having the synthetic Lyman line profiles in good
  agreement with the observed ones. In this way we are able to determine
  the structure of the magnetic dip and the thermodynamical parameters
  in the observed prominence.

---------------------------------------------------------
Title: Prominences on the Limb: Diagnostics with UV   EUV Lines and
    the Soft X-Ray Continuum
Authors: Anzer, U.; Heinzel, P.; Fárnik, F.
2007SoPh..242...43A    Altcode:
  In this paper we discuss the two mechanisms by which solar prominences
  on the limb can manifest themselves when observed in coronal UV -
  EUV lines and in the soft X-ray continuum. These mechanisms are the
  absorption in the resonance continua of hydrogen and helium on one hand
  and the reduction of the emissivity in a part of the coronal volume
  occupied by a prominence on the other one. We briefly describe earlier
  observations made with SOHO/SUMER, EIT and Yohkoh/SXT. We then discuss
  how the instruments on the new Japanese satellite Hinode can be used
  for more detailed studies of prominences. We also propose some combined
  observations between the Hinode satellite and the SOHO/SUMER instrument.

---------------------------------------------------------
Title: Spectral Diagnostics of the Magnetic Field Orientation in a
    Prominence Observed with SOHO/SUMER
Authors: Schmieder, B.; Gunár, S.; Heinzel, P.; Anzer, U.
2007SoPh..241...53S    Altcode:
  During several campaigns focused on prominences we have obtained
  coordinated spectral observations from the ground and from space. The
  SOHO/SUMER spectrometer allows us to observe, among others, the
  whole Lyman series of hydrogen, while the Hα line was observed
  by the MSDP spectrograph at the VTT. For the Lyman lines, non-LTE
  radiative-transfer computations have shown the importance of the optical
  thickness of the prominence - corona transition region (PCTR) and its
  relation to the magnetic field orientation for the explanation of the
  observed line profiles. Moreover, Heinzel, Anzer, and Gunár (2005,
  Astron. Astrophys.442, 331) developed a 2D magnetostatic model of
  prominence fine structures that demonstrates how the shapes of Lyman
  lines vary, depending on the orientation of the magnetic field with
  respect to the line of sight. To support this result observationally,
  we focus here on a round-shaped filament observed during three days as
  it was crossing the limb. The Lyman profiles observed on the limb are
  different from day to day. We interpret these differences as being due
  to the change of orientation of the prominence axis (and therefore the
  magnetic field direction) with respect to the line of sight. The Lyman
  lines are more reversed if the line of sight is across the prominence
  axis as compared to the case when it is aligned along its axis.

---------------------------------------------------------
Title: Prominence fine structures in a magnetic
    equilibrium. III. Lyman continuum in 2D configurations
Authors: Gunár, S.; Heinzel, P.; Anzer, U.
2007A&A...463..737G    Altcode:
  Aims:We discuss the behavior of the Lyman continuum profiles
  studied on the grid of 2D vertical-thread models for prominence fine
  structures. <BR />Methods: Multilevel non-LTE transfer calculations for
  a 12-level plus continuum hydrogen model atom are used. <BR />Results:
  Since the Lyman continuum is formed in regions with different
  temperatures for different orientations between the magnetic field
  direction and the line-of-sight, our Lyman continuum modeling, together
  with additional information from Lyman lines, represents a very useful
  tool for the determination of the thread structure. <BR />Conclusions:
  .A comparison between our theoretical Lyman continuum models between
  800 Å and 911 Å with the observed values shows that such a modeling
  can give interesting new constraints on the temperature structure in
  prominence threads.

---------------------------------------------------------
Title: Study of an extended EUV filament using SoHO/SUMER observations
    of the hydrogen Lyman lines
Authors: Schwartz, P.; Heinzel, P.; Schmieder, B.; Anzer, U.
2006A&A...459..651S    Altcode:
  Context: .In previous work we determined the 3D structure of an
  EUV extension of the filament observed by SoHO/CDS on 15 October
  1999. The determination of the 3D structure depends on the optical
  thickness τ<SUB>912</SUB> at the hydrogen Lyman-continuum edge at
  912 Å. The τ<SUB>912</SUB> value was unknown, therefore it was taken
  as a free parameter for the 3D-structure determinations.<BR /> Aims:
  .The plasma properties (including τ<SUB>912</SUB>) of this EUV filament
  are estimated using non-LTE modelling of profiles of the hydrogen Lyman
  lines.<BR /> Methods: .The lines Lβ, Lδ, L ɛ, L6 and L7 were observed
  by SoHO/SUMER with the slit positioned across the EUV filament. In our
  modelling the EUV filament was approximated by a horizontal 1D slab with
  constant pressure and the temperature decreasing vertically from the
  edges to interior of the slab. The values of the geometrical thickness
  of the slab in the EUV extension were taken from its 3D structure
  determined for the τ<SUB>912</SUB> values estimated iteratively. The
  synthetic profiles were fitted to observed ones using the χ<SUP>2</SUP>
  minimization.<BR /> Results: .For the Hα-filament part we obtained
  the expected results: a small geometrical thickness between several
  thousand and 15 000 km, temperatures around 5000 K in the interior and
  around 20 000 K in PCTRs, and pressure ~0.1~dyn~cm<SUP>-2</SUP>. That
  leads to an optical thickness in the Hα line center larger than 1. In
  the EUV extension, temperatures of 10 000-40 000 K in the interior
  and 35 000-50 000 K in the vertically extended PCTRs and a pressure
  of ~0.01~dyn~cm<SUP>-2</SUP> were determined. Such large variations
  of the temperature lead to large variations of τ<SUB>912</SUB>.<BR />
  Conclusions: .The EUV extension is inhomogeneous - areas both optically
  thick and thin at 912 Å are present close to each other. Parts
  optically thick at 912 Å are visible also in Hα as faint and tiny dark
  structures around the very dark and well pronounced Hα filament. The
  volume blocking mechanism is an important mechanism throughout the
  whole EUV extension even in its optically thick parts. The absorption
  dominates only in the Hα-filament part of the EUV filament.

---------------------------------------------------------
Title: Darkening of Coronal Lines by Limb Prominences Observed
    by SOHO/SUMER
Authors: Dammasch, I. E.; Heinzel, P.; Anzer, U.
2006ESASP.617E..66D    Altcode: 2006soho...17E..66D
  No abstract at ADS

---------------------------------------------------------
Title: On the Fine Structure of Solar Filaments
Authors: Heinzel, P.; Anzer, U.
2006ApJ...643L..65H    Altcode:
  High-resolution Hα images of solar filaments show a variety of
  dark fine-structure fibrils, most of them aligned with the magnetic
  field that is sheared with respect to the filament long axis. Here we
  demonstrate how such fibrils can be explained in terms of the magnetic
  field dips produced by realistic mass loading due to plasma condensation
  along the top of a magnetic prominence arcade. Our interpretation is
  supported by (2+1)-dimensional radiation-magnetohydrostatic simulations
  that predict quantitatively the properties of such condensations that
  are suspended in the dipped magnetic field.

---------------------------------------------------------
Title: A periodic arcade model for extended EUV filaments
Authors: Anzer, U.; Heinzel, P.
2006A&A...446..301A    Altcode:
  The extensions of Hα filaments that are observed in EUV spectral lines
  require the presence of cool material in a large volume surrounding
  these filaments. This material can only be supported by magnetic fields
  with dips. Such dips can be generated by a sufficiently strong twisting
  of magnetic flux tubes. In the present paper we have extended earlier
  work to more realistic magnetic field configurations that are periodic
  in the x-direction. We derived approximate equilibria for twisted
  slender flux tubes and determined the region that contains dips. In
  addition we investigated the effects on our models of the mass loading
  due to a heavy prominence. Finally we compared our theoretical models
  with the EUV - observations. We conclude that these types of models
  are capable of explaining the basic features of the observations.

---------------------------------------------------------
Title: Prominence Fine Structures in Amagnetic Equilibrium: a Grid
    Oftwo-Dimensional Models
Authors: Gunár, S.; Heinzel, P.; Anzer, U.
2005ESASP.600E..85G    Altcode: 2005dysu.confE..85G; 2005ESPM...11...85G
  No abstract at ADS

---------------------------------------------------------
Title: Radiative effects in supersonic wind accretion onto gravitating
    objects
Authors: Kryukov, I.; Pogorelov, N.; Anzer, U.; Börner, G.;
   Bisnovatyi-Kogan, G.
2005A&A...441..863K    Altcode:
  We investigate the influence of radiative effects <P />on supersonic
  wind accretion onto gravitating objects. The accreting matter is assumed
  to be optically thin. The physical mechanisms taken into account include
  cooling due to free-free and free-bound transitions, the Compton heating
  via X-ray scattering on electrons and the inverse Compton cooling in
  the regions where the temperature of the matter becomes sufficiently
  large to be able to transfer part of its internal energy to photons. A
  wide range of determining parameters was covered, including the values
  applicable to the Vela X-1 binary system, but our main emphasis is
  on the study of the effects of radiative processes on the behavior
  of accretion flows. It is shown that the applicability of polytropic
  accretion models is very limited and the actual accretion rate can
  be considerably lower than that provided by the Bondi-Hoyle-Lyttleton
  formula. The detailed consideration of the realistic radiative effects
  proved to be of great importance in our understanding of the accretion
  phenomenon, since they can substantially affect it both qualitatively
  and quantitatively.

---------------------------------------------------------
Title: Prominence fine structures in a magnetic equilibrium. II. A
    grid of two-dimensional models
Authors: Heinzel, P.; Anzer, U.; Gunár, S.
2005A&A...442..331H    Altcode:
  We construct a grid of 2D vertical-thread models for prominence fine
  structures which are in magnetohydrostatic (MHS) equilibrium. Such
  thread models have been described in a previous paper by Heinzel
  &amp; Anzer (2001), but here we use a modified 2D transfer code with
  an adaptive MHS grid. Multilevel non-LTE transfer calculations are
  now performed for a 12-level plus continuum hydrogen model atom,
  in order to study the behaviour of the Lyman-series lines observed
  by SOHO/SUMER. Our grid consists of 18 models which cover a range of
  central column masses, magnetic-field intensities and two parameters
  characterising the 2D temperature structure of the thread. Since
  different Lyman lines and their parts (line center, peak, wings) are
  formed at different places within the thread, the Lyman series may
  serve as a good diagnostic tool for thermodynamic conditions varying
  from central cool parts to a prominence-corona transition region. We
  demonstrate this behaviour for various lines, showing their synthetic
  profiles as seen from two perpendicular directions along and across
  the magnetic field lines, respectively, and displaying the respective
  contribution functions. This study confirms our earlier conclusion
  that the Lyman line profiles are much more reversed when seen across
  the field lines, compared to those seen along the lines. The latter
  can be even unreversed. We also show the geometrical cross-section
  (shape) of all 18 models. Their thread-like shape with a considerable
  aspect ratio resembles recent high-resolution Hα images. Finally,
  we discuss the relation of our thread models to the vertical threads
  studied by Fontenla et al. (1996, ApJ, 466, 496).

---------------------------------------------------------
Title: On the Nature of Dark Extreme Ultraviolet Structures Seen by
    SOHO/EIT and TRACE
Authors: Anzer, U.; Heinzel, P.
2005ApJ...622..714A    Altcode:
  Spectral lines in the extreme ultraviolet (EUV) observed on the Sun
  can originate either from the hot corona or the cooler chromosphere
  to corona transition region. In the present paper we concentrate on
  coronal lines and in particular on iron lines at 171, 195, and 284
  Å, which have been frequently observed by the Solar and Heliospheric
  Observatory (SOHO)/Extreme Ultraviolet Imaging Telescope (EIT) and the
  Transition Region and Coronal Explorer (TRACE). The intensity of these
  lines emitted by the corona can be reduced by the presence of a cool
  gas, e.g., by prominence-like material, located in the corona. There
  are two mechanisms that can lead to a reduction of the line intensity:
  absorption and volume blocking. That part of the coronal radiation
  that comes from behind the cool gas can be partially absorbed. The
  main absorbers for the iron lines studied here are neutral hydrogen
  and neutral plus singly ionized helium. In this paper we calculate
  the optical thickness of their resonance continua at the wavelength
  positions of iron lines and compare it with that in the Hα line
  center. The comparison of the derived values shows that they are quite
  similar. The second effect is due to the fact that cool structures in
  the corona do not emit any radiation in the EUV lines, which gives rise
  to an additional reduction of the observed intensity as compared with
  the surrounding corona-we have termed this “volume blocking.” We
  further describe in this paper how these two effects can be used in
  a new way of performing prominence diagnostics. Our results are also
  applicable to other coronal lines detected by, e.g., the SOHO CDS or
  SUMER instruments.

---------------------------------------------------------
Title: Determination of the 3D structure of an EUV-filament observed
    by SoHO/CDS, SoHO/SUMER and VTT/MSDP
Authors: Schwartz, P.; Heinzel, P.; Anzer, U.; Schmieder, B.
2004A&A...421..323S    Altcode:
  Heinzel et al. (\cite{hein1}) found that filaments seem to be much
  more extended in EUV spectral lines than in Hα. In this paper we
  reconstruct the 3D structure of the extensions of the EUV-filament
  observed on 15 October 1999 by SoHO/CDS and SoHO/SUMER. Small Hα
  structures were observed by VTT/MSDP. We computed the bottom and top
  heights of the EUV-filament extensions for several values of the
  hydrogen Lyman-continuum optical thickness τ<SUB>912</SUB> using
  the spectroscopic model of Heinzel et al. (\cite{hein2}). For this
  we used CDS observations of the two coronal lines Mg X 624.94 Å and
  Si XII 520.60 Å. Further, we develop a new method for estimating
  τ<SUB>912</SUB> using the O V line measured by CDS and the O VI
  measured by SUMER onboard SoHO. The latter line is used as a proxy to
  deduce the intensity variations of O V underneath the filament. This
  method also takes into account the presence of prominence-corona
  transition regions. <P />Resulting heights of the EUV-filament
  extensions are around 15 000 km for the bottom and around 40 000 km
  for the top boundaries. However, there are significant variations
  around these representative values and we show that in about half
  of observed pixels the Lyman-continuum absorption dominates in
  the coronal-line depression, while in the other half it is the
  volume blocking effect. The latter situation corresponds to a large
  (larger than 30 000 km) geometrical thickness of the EUV-filament
  extension. From the heights of the boundaries of the EUV-filament the
  geometrical thickness can be computed and used to estimate the total
  mass loading which was found to be comparable to that of typical CMEs.

---------------------------------------------------------
Title: Multiwavelength determination of the density and total mass
    of the EUV filament observed by SoHO/CDS, SoHO/SUMER and MSDP/VTT
Authors: Schwartz, P.; Schmieder, B.; Heinzel, P.; Anzer, U.
2004IAUS..223..219S    Altcode: 2005IAUS..223..219S
  It was found that filaments observed in EUV could be much more extended
  than in Halpha. These extended dark structures visible in EUV are named
  EUV filaments. Their parts seen only in EUV (not observable in Halpha
  because of low opacity at the Halpha wavelength) are called EUV-filament
  extensions (or simply EUV extensions). For the EUV filament observed
  by SoHO on 15 October 1999 as northern polar crown filament, only
  a few small dark structures were seen in Halpha. This suggests that
  the mass of the EUV extension is larger than, or at least comparable
  with, the mass of the parts of the filament observed in Halpha. In
  our previous work we determined the 3D structure of the EUV extension
  of this EUV filament. In this paper we present the determinations of
  mass and average density of this EUV extension. For better density
  estimates we interpret the hydrogen Lyman lines observed by SUMER
  using non-LTE radiative transfer code. From the best fitting of Lyman
  lines we obtained a reasonable model of the EUV extension with low gas
  pressure, temperatures from 2times10^4 K to 10^5 K and with extended
  prominence-corona transition regions.

---------------------------------------------------------
Title: A Spectroscopic Model of euv Filaments
Authors: Heinzel, P.; Anzer, U.; Schmieder, B.
2003SoPh..216..159H    Altcode:
  We propose a new spectroscopic model for extended dark structures
  around Hα filaments observed in EUV lines. As in previous papers,
  we call these structures EUV filaments. Our model uses at least three
  observed EUV lines (located shortward the hydrogen Lyman-continuum
  limit) to compute iteratively the altitudes at which the EUV filament
  extensions are located. A transition-region line (O v in the present
  case) can be used to derive the opacity of the Lyman continuum and the
  other two coronal lines (e.g., Mg x and Si xii) then give two heights:
  the bottom and top of the EUV filament. The method takes into account
  self-consistently the absorption of EUV-line radiation by the Lyman
  continuum, as well as the volume-blocking effect potentially important
  for coronal lines. As an example we compute the heights of the EUV
  filament at one particular position, using CDS data for the 5 May 2000
  filament. At this position, the EUV filament extension lies between
  altitudes 28 700 and 39 000 km, so that the geometrical thickness of the
  structure is 10300 km (we discuss also the sensitivity of our models
  to variations of the line intensities). These heights are consistent
  with the concept of twisted magnetic flux tubes, but there could be
  also some influence on our results due to additional low lying cool
  structures from parasitic polarities.

---------------------------------------------------------
Title: Determination of the 3D-topology of an EUV-filament observed
    by SoHO/CDS SoHO/SUMER and VTT/MSDP
Authors: Schwartz, P.; Heinzel, P.; Schmieder, B.; Anzer, U.
2003ESASP.535..495S    Altcode: 2003iscs.symp..495S
  We have constructed a spatial model of an extended EUV-filament
  observed on 15 October 1999 (polar crown N 38 deg) by SoHO/CDS. The
  narrow Hα counterparts were observed by VTT/MSDP. As found in 2001,
  EUV-filaments are much more extended than those parts visible in Hα. We
  have computed the bottom and top heights of this EUV-filament for the
  whole CDS raster for different values of the Lyman-continuum optical
  thickness using CDS measurements of two coronal lines (Mg X 624.94
  Å and Si XII 520.60 Å) and the model of Heinzel et al., 2003. For
  the scale height of the MgX line we used the value from Fludra et
  al. 1999, assuming that this line is not solar cycle and activity
  dependent. We created a new method for τ<SUB>912</SUB> determination
  from O VI and O V line intensities. Because of the inhomogeneity in
  the O V 629.37 Å line intensity distribution in the vicinitiy of
  the EUV-filament it was not possible to estimate this intensity under
  the filament. So we used observations made by SoHO/SUMER of the O VI
  1031.91 Å line not absorbed by EUV-filament cold plasma. The knowledge
  of the heights of the bottom and top boundaries of an EUV-filament
  gives us the EUV-filament geometrical thickness. From this the mass
  of the EUV-filament was computed.

---------------------------------------------------------
Title: EUV-filaments and their mass loading
Authors: Heinzel, P.; Anzer, U.; Schmieder, B.; Schwartz, P.
2003ESASP.535..447H    Altcode: 2003iscs.symp..447H
  It was found recently (Heinzel et al., 2001; Schmieder et al., 2003)
  that solar filaments observed in EUV lines by SOHO/CDS are much more
  extended than their Hα counterparts. This was explained by a large
  difference between the hydrogen Lyman-continuum and Hα opacities. Two
  different MHD models were suggested to explain the EUV-filament
  extensions: the model based on parasitic polarities (Aulanier &amp;
  Schmieder, 2002) and the model with twisted flux tubes (Anzer &amp;
  Heinzel, 2003). The latter model can explain our recent findings
  that at least some parts of the EUV-filament extensions are located
  relatively high in the corona. These heights can be computed using a
  new spectroscopic model of EUV-filaments. The mass which is loaded into
  the EUV-filament extensions is then estimated on the basis of non-LTE
  transfer calculation. The total filament mass is larger than that
  derived for the Hα filament itself and this may have consequences
  for the structure and mass loading of CMEs whenever they form from
  such filaments - this may answer the question how the extended CME
  structures can form from rather narrow Hα filaments. We summarize
  the basic properties of EUV-filaments, present their spectroscopic
  analysis and give some estimates for mass loading. We then discuss
  possible relations between EUV-filaments and CMEs, in particular the
  problems of their masses.

---------------------------------------------------------
Title: On the nature of extended EUV filaments
Authors: Anzer, U.; Heinzel, P.
2003A&A...404.1139A    Altcode:
  This paper describes the properties of extended EUV filaments and the
  theoretical modelling of them. We summarise the general aspects of the
  depression of EUV-line emission and give an interpretation of recent
  filament observations in transition-region and coronal lines. The
  EUV filament was found to be located relatively high in the corona
  (at least 20 000 km above the solar surface) and this requires an
  MHD scenario alternative to the parasitic-polarity model of Aulanier
  &amp; Schmieder (\cite{Aulanier02}). Here we present a new idea
  for the support of cool gas in the magnetic arcade of a prominence
  which is capable of explaining both wide and vertically extended EUV
  filaments. Our mechanism is based upon the twisting of individual
  flux tubes, similar to the one which was suggested by Priest et
  al. (\cite{Priest89}). Finally, the consequences of this new model
  are discussed.

---------------------------------------------------------
Title: The influence of radiative effects on the accretion onto
    stellar magnetospheres
Authors: Kryukov, I. A.; Pogorelov, N. V.; Anzer, U.; Bisnovatyi-Kogan,
   G. S.; Börner, G.
2003A&A...402...13K    Altcode:
  The influence of radiative effects on the accretion onto stellar
  magnetospheres is investigated by performing global 2- and
  2.5-dimensional simulations on the basis of high-resolution numerical
  schemes with the application of irregular grids adapted to the shape
  of the magnetopause. The latter is represented by an impermeable,
  contracted dipole magnetic field surface with polar holes. Accreting
  matter is assumed to be optically thin. The physical mechanisms which
  are taken into account include cooling due to free-free and free-bound
  transitions, the Compton heating via X-ray scattering on electrons, and
  the inverse Compton cooling in the regions where the temperature of the
  matter becomes sufficiently large to be able to transfer part of its
  internal energy to photons. Depending on the determining parameters,
  both steady-state solutions with a system of discontinuities and
  unsteady flows with expanding shock waves can be obtained. It is shown
  that efficient cooling of the matter can substantially facilitate
  the penetration of the matter through the polar holes. The detailed
  consideration of the realistic radiative effects proved to be of great
  importance in our understanding of the accretion phenomenon, since
  they can substantially affect it both qualitatively and quantitatively.

---------------------------------------------------------
Title: 2D Radiative Transfer in Magnetically Confined Structures
Authors: Heinzel, P.; Anzer, U.
2003ASPC..288..441H    Altcode: 2003sam..conf..441H
  Magnetically confined structures in the solar atmosphere exhibit
  a large complexity in their shapes and physical conditions. As an
  example, we show the case of so-called magnetic dips in prominences
  which are in magnetohydrostatic equilibria. For such models we solve
  2D non-LTE multilevel problem for hydrogen with PRD in Lyman resonance
  lines. The iterative technique used is based on the MALI approach with
  simple diagonal ALO and SC formal solver. <P />To compute the hydrogen
  ionization balance, the preconditioned MALI equations are linearized
  with respect to atomic level populations and electron density and
  solved iteratively using the Newton-Raphson scheme. Two additional
  problems are addressed: (i) an adequate iteration method for cases when
  the column-mass scale is used in one of the two dimensions but varies
  along the other dimension (which has a geometrical scaling); and (ii)
  a possibility of using AMR (Adaptive Mesh Refinement) algorithms to
  account for steep 2D gradients of selected variables (temperature,
  density, etc.).

---------------------------------------------------------
Title: Radiative Effects in the Modelling of Accretion onto Stellar
    Magnetospheres
Authors: Pogorelov, Nikolai; Kryukov, Igor; Anzer, Ulrich;
   Bisnovatyi-Kogan, Guennadii; Börner, Gerhard
2003acfp.conf..473P    Altcode:
  Accretion onto neutron stars and black holes is the main energy supply
  in galactic X-ray sources. The angular momentum captured by the X-ray
  star from the optical companion's wind with velocity V_{infty} and
  the binary period P is proportional to V^{-4}_{infty}P^{-1} [4]. If
  V_{infty} is high or the binary components are widely separated, the
  angular momentum is not sufficient for the accretion disk formation
  at distances of the Alfvén radius where the magnetic pressure of the
  star is balanced by the dynamic pressure of infalling matter, and the
  accretion at large distances from the star becomes nearly spherically
  symmetric. This occurs, for example, in some X-ray sources with a
  massive companion star where long-periodic pulsars are observed [1],
  [3].

---------------------------------------------------------
Title: A prominence with transition region: horizontal two-dimensional
    filament model
Authors: Gorshkov, A. B.; Anzer, U.; Heinzel, P.
2002ESASP.506..405G    Altcode: 2002ESPM...10..405G; 2002svco.conf..405G
  SOHO/SUMER observations of solar filaments in Lyman lines of hydrogen
  have revealed, in general, a two-peak form of the emission line
  profiles with peak to center ratio less than an order of magnitude. This
  fact strongly contradicts the results of numerical radiative transfer
  simulations, where profiles with strong dips and large (1.5-2 orders of
  magnitude) peak to center ratio are usually obtained due to the absence
  of incident radiation from above the filament and, as a consequence,
  very low atomic populations on the upper energy levels at the top of
  the filament. Recently it was shown (Schmieder et al. 1998) that this
  discrepancy can be removed by introducing a prominence-corona transition
  region (PCTR) to the radiative transfer models. This paper continues
  a set of publications (Anzer &amp; Heinzel, 1999 and Heinzel &amp;
  Anzer, 2001) devoted to the modelling of prominences as structures in
  MHS equilibrium. Here the prominence is represented by a horizontal
  2D slab supported by a magnetic field. In our model we use a constant
  gas pressure and assume that the kinetic temperature profile and the
  PCTR extension are different in the vertical and horizontal directions
  due to magnetic field. In the PCTR the temperature sharply increases
  outwards from 8000K to 50000K on the scale of 100-600 km. To solve
  the radiative transfer problem we apply a 2D code based on the MALI
  iteration scheme and the modified long characteristics method.

---------------------------------------------------------
Title: Magnetic dips and the physics of quiescent prominences
Authors: Anzer, Ulrich
2002ESASP.506..389A    Altcode: 2002svco.conf..389A; 2002ESPM...10..389A
  This paper discusses the recent developments of prominence
  modelling. The basic aspect of our discussion is the presence of
  magnetic dips in all the models. We first show that "initial" dips
  are needed for prominence formation and stability. We then give some
  typical examples for different field configurations with dips. Next we
  discuss those dips which are required for prominence support. We present
  both 1D (slab) and 2D (thread) models. In addition the problem with the
  theoretical modelling of extended EUV filaments is described. Then we
  explain the difficulties with the observational confirmation of dipped
  structures. We also comment on a model which suggests that equilibria
  can be obtained for configurations without dips and finally we summarise
  the most relevant aspects.

---------------------------------------------------------
Title: Spectral diagnostics of the magnetic field orientation in a
    round-shaped filament
Authors: Schmieder, B.; Mein, N.; Heinzel, P.; Anzer, U.
2002ESASP.506..469S    Altcode: 2002ESPM...10..469S; 2002svco.conf..469S
  During several campaigns focused on prominences we have obtained
  coordinated spectral observations from the ground and from space. The
  SOHO/SUMER spectrometer allows us to observe, among others, the whole
  Lyman series of hydrogen, while the Hα line was observed by the MSDP
  spectrograph at the VTT. For Lyman lines, the non-LTE radiative-transfer
  computations have shown the importance of the prominence-corona
  transition region (PCTR) and its relation to the magnetic field
  orientation for the explanation of the observed line profiles (Schmieder
  et al. 1998, Heinzel et al. 2001). Moreover, Heinzel and Anzer (2001)
  developed new 2D models which demonstrate how the shapes of Lyman
  lines vary depending on the orientation of the magnetic field with
  respect to the line of sight. To confirm this result observationally,
  we focus here on a round-shaped filament observed during three days
  as it was crossing the limb. The Lyman profiles observed on the limb
  are different from day to day and we interpret these differences by
  the change of orientation of the prominence axis (and therefore the
  magnetic field direction) with respect to the line-of-sight.

---------------------------------------------------------
Title: Prominence fine structures in a magnetic equilibrium:
    Two-dimensional models with multilevel radiative transfer
Authors: Heinzel, P.; Anzer, U.
2001A&A...375.1082H    Altcode:
  In this paper we construct theoretical models for vertical prominence
  threads which are in magnetohydrostatic (MHS) equilibrium. These
  models are fully two-dimensional (2D) and take the form of vertically
  infinite threads hanging in a horizontal magnetic field. A typical
  example of such a 2D magnetic-dip structure is shown for the case
  when the central cool parts are surrounded by the prominence-corona
  transition region (PCTR). We display 2D variations of the pressure,
  density and temperature. While the pressure variations follow from the
  MHS equilibrium, the kinetic temperature was specified empirically. As a
  next step, we have solved the 2D multilevel non-LTE transfer problem in
  such thread-like structures, in order to predict the spatial variations
  of the emergent hydrogen spectrum. It is demonstrated that the hydrogen
  Lyman lines (treated with partial redistribution) show significant
  spatial variations of the intensity and that an important difference
  exists between the line profiles emergent along and across the magnetic
  field lines. We also discuss how these intensity variations compare to
  recent SOHO/SUMER prominence observations, namely we show the effects
  of line-profile averaging over the fine-structure threads which are
  below the instrumental resolution. Finally we make some suggestions
  for future modelling and observations.

---------------------------------------------------------
Title: Hydrodynamic modeling of accretion onto stellar magnetospheres
Authors: Kryukov, I. A.; Pogorelov, N. V.; Bisnovatyi-Kogan, G. S.;
   Anzer, U.; Börner, G.
2000A&A...364..901K    Altcode:
  A numerical investigation is performed of the accretion of slowly
  rotating matter onto a stellar magnetosphere. The shape of the
  magnetosphere is represented by an impermeable, contracted dipole
  magnetic field surface with polar holes. Depending on the governing
  parameters, both steady-state solutions with a system of discontinuities
  and unsteady flows with expanding shock waves can be obtained. Certain
  solutions exhibit extended outflow regions. The simulation is performed
  using a high-resolution finite volume numerical scheme and structured
  irregular grids adapted to the shape of the accreting body.

---------------------------------------------------------
Title: Energy considerations for solar prominences with mass inflow
Authors: Anzer, U.; Heinzel, P.
2000A&A...358L..75A    Altcode:
  In this Letter we study the inflow of enthalpy and ionisation
  energy into solar prominences. We use 1D stationary slab models for
  the prominence to calculate this inflow. We compare the resulting
  energy gain with the integrated radiative losses obtained for such
  slab models. We find that for reasonable inflow velocities many of our
  models can be in energy equilibrium; only the very massive prominences
  will either require some additional heating or they have to cool down
  to low central temperatures. We also discuss the possibility or heating
  the prominence by vertical downflows.

---------------------------------------------------------
Title: The energy balance in solar prominences
Authors: Anzer, U.; Heinzel, P.
1999A&A...349..974A    Altcode:
  In this paper we study the energy balance in quiescent solar
  prominences. For this investigation we use a simple 1D slab model in
  magneto-hydrostatic equilibrium. We divide the studied region into two
  parts: The inner region consisting of the prominence itself and the
  cool part of the transition region (up to 30000 K). In this region the
  plasma is optically thick in several atomic transitions and therefore we
  have to solve the non-LTE radiative transfer problem in this part. This
  allows us to derive self-consistently the gas density, the ionization
  degree of hydrogen and the hydrogenic radiation losses. The energy
  transport by thermal conduction can be neglected in this region. In the
  outer part of the transition region, the thermal conduction becomes very
  important but the treatment of radiation is simplified by the fact that
  the plasma is optically thin. We find that energy balance in prominences
  can only be obtained for special forms of the heating function. This
  requirement is very stringent for the inner parts, while in the outer
  region thermal conduction can transport large amounts of the heat
  energy and therefore a wider class of heating functions will be allowed.

---------------------------------------------------------
Title: Magnetic Dips in Prominences
Authors: Heinzel, P.; Anzer, U.
1999SoPh..184..103H    Altcode:
  Magnetic dips are generally assumed to be basic equilibrium
  configurations in quiescent solar prominences. Here we discuss two types
  of the magnetic dips which were considered in the literature: (1) dips
  resulting from a force-free magnetic equilibrium in the corona, and (2)
  magnetic dips which are formed in situations where the Lorentz force
  balances the weight of the prominence plasma. An important parameter
  which decides between these two cases is the plasma β. For β⋘1,
  the effect of the prominence material on the equilibrium structure is
  quite negligible and the case (1) holds. If, however, β is larger,
  say between 0.1 and 1 or even higher, magnetic dips of the second kind
  are formed and they can be characterized by the angle ψ1 between the
  vertical and the direction of the field lines at the surface of the
  prominence structure. A simple and illustratory formula is derived
  to relate this angle to the plasma β at the prominence center,
  namely βc≃cot2ψ1. βc=1 thus corresponds to ψ1=45°. Finally,
  we discuss the range of values of both βc and ψ1 as deduced from
  various observations and conclude that the dips of the second kind are
  important for the prominence equilibria. We also suggest a new method
  for determination of the field-line inclination.

---------------------------------------------------------
Title: Numerical Computation of Two-Dimensional Wind Accretion of
    Isothermal Gas
Authors: Shima, E.; Matsuda, T.; Anzer, U.; Börner, G.; Boffin,
   H. M. J.
1999ASSL..240..225S    Altcode: 1999numa.conf..225S
  No abstract at ADS

---------------------------------------------------------
Title: Numerical computation of two dimensional wind accretion of
    isothermal gas
Authors: Shima, Eiji; Matsuda, Takuya; Anzer, Ulrich; Boerner, Gerhard;
   Boffin, Henri M. J.
1998A&A...337..311S    Altcode: 1998astro.ph..5343S
  A new numerical algorithm for calculating isothermal wind accretion
  flows has been developed and is applied here to the analysis of the
  hydrodynamics of two-dimensional plane symmetric accretion flows in
  wind-fed sources. Polar coordinates are used to ensure fine resolution
  near the object. It is found that a thin accretion column is formed
  which shows wave-like oscillations. Small accretion disks are formed
  temporarily around the object. Mass accretion rate and angular momentum
  accretion rate exhibit quasi-periodic oscillations. The amplitudes of
  the oscillations depend on the size of the inner boundary, the number
  of grid points and the method of calculation. For a smaller size of
  the inner boundary, finer grids and more accurate numerical schemes,
  the amplitudes of the oscillation become larger.

---------------------------------------------------------
Title: Prominence Parameters Derived from Magnetic-Field Measurements
    and NLTE Diagnostics
Authors: Anzer, U.; Heinzel, P.
1998SoPh..179...75A    Altcode:
  In this paper we present a detailed analysis of a number of quiescent
  prominences for which the components of the magnetic field as well as
  the electron density and emission measure were previously obtained from
  quasi-simultaneous measurements in hydrogen Hα and helium D<SUB>3</SUB>
  lines. From magnetic equilibrium models of the Kippenhahn-Schlüter
  type one can calculate the gas pressure, density, column mass and
  geometrical width. The same set of physical parameters can also
  be derived from a NLTE hydrogen-line analysis. We have studied the
  mutual correlations between these two sets of parameters. Very large
  differences, reaching an order of magnitude, were found between these
  two sets, both for individual prominences and for the mean values over
  all prominences used in this investigation. Finally, we discuss some
  implications of our results.

---------------------------------------------------------
Title: Modelling of Non-Uniform Prominence Slabs
Authors: Heinzel, P.; Anzer, U.
1998ASPC..150..213H    Altcode: 1998IAUCo.167..213H; 1998npsp.conf..213H
  No abstract at ADS

---------------------------------------------------------
Title: VELA X-1: how to produce asymmetric eclipses.
Authors: Feldmeier, A.; Anzer, U.; Boerner, G.; Nagase, F.
1996A&A...311..793F    Altcode:
  Light curves of the X-ray pulsar Vela X-1 obtained with the ASCA
  satellite show a strong asymmetry in the hard energy band during
  the eclipse of the X-ray source: a steep drop at ingress is followed
  by a gradual decline, whereas only a steep increase is observed at
  egress. X-ray scattering off the dense accretion wake trailing the
  neutron star cannot explain the gradual decline because of the long
  persistence of the latter ({DELTA}φ=0.11). Instead we propose that
  scattering in an extended photoionization wake is responsible. This
  wake is caused by the switch-off of the radiative force that drives
  the B supergiant wind during the passage through the highly ionized
  Stroemgren region surrounding the X-ray source. The stalled gas then
  trails the neutron star, which moves relative to the B star surface (no
  corotation). A model for the Vela X-1 system which assumes that the B
  star does not rotate gives too large a phase extent for the dense wake
  and can be ruled out. Including the B star rotation in an approximate
  way, the relative azimuthal motion of the neutron star is slower and
  the wake covers a smaller phase interval. Finally, we assume that the
  Stroemgren sphere does not reach too deep into the wind accelerating
  region. The wind can then reach a certain fraction of the terminal
  velocity before the radiative force is switched off. This elongates
  the photoionization wake further and both its phase extent and its
  scattering efficiency match the observations.

---------------------------------------------------------
Title: Modeling Accretion onto a Closed Pulsar Magnetosphere
Authors: Morris, J. P.; Boerner, G.; Anzer, U.
1995AAS...187.3306M    Altcode: 1995BAAS...27Q1330M
  A method for modeling accretion onto a closed magnetosphere employing
  the numerical method of SPH is presented. This method allows the dynamic
  interaction of the magnetosphere and surrounding field-free plasma to be
  simulated. Results obtained for some steady configurations are compared
  with previous work for closed magnetospheres. Future application of the
  technique, with a view to modeling spin up and spin down of pulsars is
  discussed. Other possible applications and enhancements of the method
  are outlined.

---------------------------------------------------------
Title: Parameters of Quiescent Prominences Derived from Magnetic
    Field Measurements
Authors: Anzer, Ulrich
1995SoPh..161...49A    Altcode:
  Based upon the new magnetic field vector measurements of
  Bommieret al. (1994) we construct prominence models which are in
  magnetohydrostatic equilibrium. We compare these new models with
  earlier ones and find that they are on average more massive and also
  considerably narrower.

---------------------------------------------------------
Title: Random variations of the pulse period of X-ray binaries with
    wind accretion.
Authors: Anzer, U.; Boerner, G.
1995A&A...299...62A    Altcode:
  In this paper we first summarise earlier results about the randomness
  of pulse period variations in wind fed X-ray pulsars. Then we
  present two types of models for the random spin-up and spin-down of
  rotating neutron stars which accrete mass from a stellar wind. We
  show that the irregularities in accretion flows which were discovered
  in numerical models have too low amplitudes in order to explain the
  observations. Therefore we discuss an alternative model which is based
  upon the existence of a Kepler disc around the neutron star. We argue
  that such a model can give an explanation of the observations.

---------------------------------------------------------
Title: Book Review: Fragmented energy release in sun and stars,
    the interface between MHD and plasma physics / Kluwer, 1994
Authors: Anzer, U.
1995SoPh..158R.399V    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Book reviews
Authors: Valníček, B.; Anzer, U.
1995SoPh..158..399V    Altcode: 1995SoPh..158..399A
  No abstract at ADS

---------------------------------------------------------
Title: Bondi-Hoyle accretion simulations including velocity gradients.
Authors: Ruffert, M.; Anzer, U.
1995A&A...295..108R    Altcode:
  We investigate the hydrodynamics of three-dimensional classical
  Bondi-Hoyle accretion, especially the accretion of angular momentum
  from a non-homogeneous medium and discuss some consequences for models
  of wind-fed X-ray sources. A medium taken to be an ideal gas (γ=5/3)
  moves at Mach 3 past a totally absorbing sphere with a radius of 0.1
  accretion radii. The velocity of this medium is given a gradient of 3%
  (per accretion radius distance) perpendicular to the bulk flow. The
  hydrodynamics is modeled by the "Piecewise Parabolic Method" and
  the resolution around the accretor is increased using 7 multiply
  nested grids. The flow in the shock cone is not steady, but does not
  exhibit large scale "flip-flop"-flow. The average specific angular
  momentum accreted is 0.097 (in units of accretion radii and sound
  speed). Although the magnitude is large compared to cases without
  velocity gradient, it still is not large enough to sustain the random
  walk model of wind-fed X-ray sources.

---------------------------------------------------------
Title: Numerical studies of wind accretion using SPH I. 2D
    simulations.
Authors: Boffin, Henri M. J.; Anzer, Ulrich
1994A&A...284.1026B    Altcode:
  Two-dimensional numerical simulations of accretion by a gravitating
  object from a homogeneous wind are performed using SPH. The effects of
  several parameters changes as well as the algorithm modifications are
  studied. The flow is in most cases weakly unstable with a very small,
  quasi-periodic oscillation of the shock cone. Comparison with previous
  works is also done.

---------------------------------------------------------
Title: Remarks on Two-Dimensional Magnetic Arcade Models of Coronal
    Structures
Authors: Anzer, U.
1994scs..conf..309A    Altcode: 1994IAUCo.144..309A
  A critical evaluation of some recent models for coronal structures using
  two-dimensional magnetic arcades is given. Prominences with inverse
  polarity as well as the evolution of sheared arcades are discussed.

---------------------------------------------------------
Title: Tests of Wind Accretion Models
Authors: Anzer, U.; Börner, G.; Nagase, F.
1994nhxr.conf..611A    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: A simple analysis of period noise in binary X-ray pulsars.
Authors: de Kool, Martijn; Anzer, Ulrich
1993MNRAS.262..726D    Altcode:
  A simple method is presented for determining whether the noise in the
  pulse period history of X-ray pulsars can be described by a random
  walk process. This is accomplished by calculating the mean difference
  in angular velocity between different observations as a function of
  the time interval between these observations. The method is applied
  to 10 X-ray pulsars for which more than 10 period determinations
  are available. For Vela X-1, earlier results that the pulse period
  behavior is very well fitted by a random walk in period is confirmed. In
  GX 301-2 the pulse period behavior is also consistent with a random
  walk. Analysis of the pulse period history of three X-ray pulsars with
  a Be companion shows that a random walk is not consistent with the data.

---------------------------------------------------------
Title: Numerical Simulations of Two-dimensional and Three-dimensional
    Wind Accretion Flows of an Isothermal Gas
Authors: Ishii, Takanori; Matsuda, Takuya; Shima, Eiji; Livio, Mario;
   Anzer, Ulrich; Boerner, Gerhard
1993ApJ...404..706I    Altcode:
  We present the results of 2D and 3D numerical hydrodynamical
  calculations of accretion flows of an isothermal gas past a gravitating
  compact object. The calculations were performed both for a homogeneous
  medium and for a medium containing a transverse density or velocity
  gradient. We find that 2D isothermal flows exhibit the 'flip-flop'
  instability (previously seen in adiabatic calculations) both in the
  homogeneous and the inhomogeneous cases. In the 3D case, while some
  unsteadiness is observed, the instability is much less violent than
  in 2D. We calculate (for the first time with a 3D hydrocode) the
  rate of accretion of mass and angular momentum from an inhomogeneous
  medium. The mass accretion rate agrees quite well with the prediction
  of the Bondi-Hoyle theory. However, the rate of accretion of angular
  momentum is considerably lower than the rate at which angular momentum
  is deposited into the accretion cylinder. A possible consequence of
  our results for wind-fed X-ray binaries is discussed.

---------------------------------------------------------
Title: Some Aspects of Magnetic Arcades in the Solar Corona
Authors: Anzer, U.
1993ComAp..16..305A    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Variations of the pulse periods in X-ray binaries: modelling
    attempts
Authors: Anzer, U.
1993heac.conf...15A    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: The Fibril Structure of Prominences
Authors: Hood, A. W.; Priest, E. R.; Anzer, U.
1992SoPh..138..331H    Altcode:
  In this paper we present several magneto-hydrostatic equilibrium
  models for prominences with fibril-like fine structure. For all the
  models ad hoc temperature profiles are used without discussing the
  energetics. For our models we assume fine structure to occur either
  across the prominence axis or along it. This approach is intended
  as a first step towards more realistic models based upon a series of
  vertical fibril structures.

---------------------------------------------------------
Title: Numerical simulations of two-dimensional and three-dimensional
    accretion flows
Authors: Matsuda, Takuya; Ishii, Takanori; Sekino, Nobuhiro; Sawada,
   Keisuke; Shima, Eiji; Livio, Mario; Anzer, Ulrich
1992MNRAS.255..183M    Altcode:
  Numerical simulations of 2D and 3D accretion flows past a gravitating
  compact object from a uniform flow at a large distance upstream are
  performed by solving the Eulerian equations. The 2D flows exhibit a
  'flip-flop instability' if the central accreting body is small. If
  the central body is enlarged at some instance in the oscillating flow,
  then the accretion shock shows a rather periodic oscillation similar
  to the von Karman vortex street. In the case of 3D flows, it is found
  that the shock cone is much more robust than in 2D, and the flip-flop
  instability takes a different, probably less violent, form. The causes
  of the instabilities are discussed.

---------------------------------------------------------
Title: Pulsating X-Ray Sources - Longterm Period Variations
Authors: Anzer, U.; Borner, G.
1992ComAp..16...31A    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Flip-Flop Instability of Wind-Fed Accretion Flow - 2D and
    3D Calculations
Authors: Matsuda, T.; Ishii, T.; Livio, M.; Anzer, U.; Börner, G.
1992fxra.conf..177M    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: On the 'flip-flop' instability of Bondi-Hoyle accretion flows
Authors: Livio, Mario; Soker, Noam; Matsuda, Takuya; Anzer, Ulrich
1991MNRAS.253..633L    Altcode:
  A simple physical interpretation is advanced by means of an analysis
  of the shock cone in the accretion flows past a compact object and with
  an examination of the accretion-line stability analyses. The stability
  of the conical shock is examined against small angular deflections with
  attention given to several simplifying assumptions. A line instability
  is identified in the Bondi-Hoyle accretion flows that leads to the
  formation of a large opening-angle shock. When the opening angle becomes
  large the instability becomes irregular oscillation. The analytical
  methodology is compared to previous numerical configurations that
  demonstrate different shock morphologies. The Bondi-Hoyle accretion
  onto a compact object is concluded to generate a range of nonlinear
  instabilities in both homogeneous and inhomogeneous cases with a
  quasiperiodic oscillation in the linear regime.

---------------------------------------------------------
Title: On the stability of wind accretion.
Authors: Matsuda, T.; Sekino, N.; Sawada, K.; Shima, E.; Livio, M.;
   Anzer, U.; Boerner, G.
1991A&A...248..301M    Altcode:
  Results of numerical investigations of accretion flows past a compact
  object are reported. A strong tendency toward nonsteady flow is
  found to exist in both 2D and 3D computations. Steady flows are
  obtained only when the numerical resolution is low or the central
  absorbing body is large. It is concluded that: (1) accretion from a
  homogeneous medium onto a compact object is intrinsically nonsteady;
  (2) the instability manifests itself in 'flip-flop' oscillations of
  the accretion shock cone, accompanied by short phases of quasi-disk
  formation, with the sense of rotation reversing periodically; and (3)
  no density or velocity gradients in the incoming flow are required
  for the instability to develop.

---------------------------------------------------------
Title: The Fibril Structure of Prominences
Authors: Priest, E. R.; Hood, A. W.; Anzer, U.
1991SoPh..132..199P    Altcode:
  We suggest that the fibril structure of prominences may be caused by
  filamentation during its formation by radiative instability. We also
  discuss the effects of other types of instability and give a mechanism
  for the formation of vertical threads. The models indicate that highly
  inhomogeneous density structures can exist in the presence of smooth
  profiles for the plasma pressure and magnetic field. In our particular
  models the plasma pressure of a fibril prominence is higher and the
  vertical magnetical field is weaker than in a uniform prominence model,
  while the mass is substantially smaller.

---------------------------------------------------------
Title: Binary X-Ray Sources: Some Aspects of Wind Accretion
Authors: Anzer, U.; Börner, G.
1991heac.conf....3A    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Magnetic Field Configurations which can Produce Prominences
    with Inverse Polarity
Authors: Anzer, U.
1990SoPh..130..403A    Altcode:
  In this Letter several observational aspects of prominences with inverse
  magnetic polarity are summarised. It is shown that these features can
  be explained in a natural way if inverse polarity prominences result
  from the merging of two adjacent bipolar magnetic regions.

---------------------------------------------------------
Title: Prominence models with line currents - Stabilisation by
    flux conservation
Authors: Anzer, U.; Ballester, J. L.
1990A&A...238..365A    Altcode:
  A model of prominence eruption, based on a filament with circular cross
  section as different from the filament of a single line current used in
  earlier models, is presented. For configurations with normal and inverse
  polarity, the model is considered to be stable with respect to the
  vertical displacements. This implies that simple configurations cannot
  model prominence eruptions unless the effect of flux conservation is
  also included. It is found that if the magnetic flux below a finite size
  filament is conserved, a run-away instability no longer exists. The
  results apply to a limited class of 2-D equilibria containing a
  cylindrical filament and subjected to strictly 2-D perturbation. Models
  that are more realistic can be unstable.

---------------------------------------------------------
Title: A Model for Quiescent Solar Prominences with Normal Polarity
Authors: Hood, A. W.; Anzer, U.
1990SoPh..126..117H    Altcode:
  A class of 2-D models of solar quiescent prominences, with normal
  polarity, is presented. These represent an extension to the
  Kippenhahn-Schlüter model for which the prominence configuration
  matches smoothly onto an external non-potential coronal solution
  of a constant α field. Using typical prominence values a model is
  constructed which also matches the coronal conditions. It is found
  that the magnetic field component along the prominence influences
  the internal structure of the prominence. A simple extension to the
  basic models is indicated as a means of taking a lower boundary of
  the prominence and eliminating parasitic polarities in the photosphere.

---------------------------------------------------------
Title: Structure and stability of prominences
Authors: Anzer, U.
1990GMS....58..307A    Altcode:
  The present consideration of the magnetohydrostatic equilibria of
  quiescent solar prominences proceeds from the conceptual framework of
  field configurations having normal and inverse magnetic polarities to an
  evaluation of the principal models for both types of configuration. A
  novel model based on the twisted flux tube phenomenon is presented
  with a view to the visualization of the prominence as a sheet within
  such a flux rope. Questions as to the energy balance of prominences
  are left out of account.

---------------------------------------------------------
Title: Prominence Models with Line Currents: Stabilization by Flux
    Conservation
Authors: Anzer, U.; Ballester, J. L.
1990PDHO....7..156A    Altcode: 1990ESPM....6..156A; 1990dysu.conf..156A
  No abstract at ADS

---------------------------------------------------------
Title: A normal polarity quiescent prominence model.
Authors: Hood, A. W.; Anzer, U.
1990PDHO....7..130H    Altcode: 1990dysu.conf..130H
  A class of simple 2-D non-isothermal models for quiescent
  prominences with normal polarity are presented. These extended the
  Kippenhahn-Schlüter and Menzel models by smoothly matching the
  prominence region onto an external, force-free coronal field. In
  addition, the field component along the prominences is an integral
  part of the solution and modifies the internal structure.

---------------------------------------------------------
Title: A Model for Quiescent Solar Prominences with Normal Polarity
Authors: Hood, A. W.; Anzer, U.
1990LNP...363..271H    Altcode: 1990doqp.coll..271H; 1990IAUCo.117..271H
  No abstract at ADS

---------------------------------------------------------
Title: A three-dimensional model for solar prominences
Authors: Démoulin, P.; Priest, E. R.; Anzer, U.
1990LNP...363..268D    Altcode: 1990doqp.coll..268P; 1990LNP...363..268P; 1990IAUCo.117..268P
  We suggest here a model for the 3D structure of quiescent prominences by
  a superposition of two fields. A 3D force-free field with constant is
  assumed to exist in the corona prior to the prominence formation. The
  prominence itself is represented by a line current which interacts
  with the coronal field. The three-dimensional field is represented by
  analytical functions and concentration of the magnetic field at the
  photospheric level by convection cells is taken into account. When the
  field created by the photospheric pattern supports the prominence,
  the prominence feet are found to be located at supergranule centres
  otherwise; they are located at cell boundaries.

---------------------------------------------------------
Title: A three-dimensional model for solar prominences
Authors: Demoulin, P.; Priest, E. R.; Anzer, U.
1989A&A...221..326D    Altcode:
  In an attempt to model the external force field of a prominence,
  a three-dimensional linear force-free field configuration was
  studied. The model consists of a fundamental together with a harmonic
  that is periodic along the prominence. The variation of the prominence
  height along the prominence is calculated and it is suggested that
  feet occur where the prominence sags down to low heights.

---------------------------------------------------------
Title: A Twisted Flux-Tube Model for Solar Prominences. I. General
    Properties
Authors: Priest, E. R.; Hood, A. W.; Anzer, U.
1989ApJ...344.1010P    Altcode:
  It is proposed that a solar prominence consists of cool plasma supported
  in a large-scale curved and twisted magnetic flux tube. As long as
  the flux tube is untwisted, its curvature is concave toward the solar
  surface, and so it cannot support dense plasma against gravity. However,
  when it is twisted sufficiently, individual field lines may acquire a
  convex curvature near their summits and so provide support. Cool plasma
  then naturally tends to accumulate in such field line dips either
  by injection from below or by thermal condensation. As the tube is
  twisted up further or reconnection takes place below the prominence, one
  finds a transition from normal to inverse polarity. When the flux tube
  becomes too long or is twisted too much, it loses stability and its true
  magnetic geometry as an erupting prominence is revealed more clearly.

---------------------------------------------------------
Title: Inhomogeneous wind accretion - Comparison between 3D and
    2D computations
Authors: Sawada, K.; Matsuda, T.; Anzer, U.; Boerner, G.; Livio, M.
1989A&A...221..263S    Altcode:
  Full three-dimensional computations of accretion flows which have
  velocity gradients are presented and compared with two-dimensional
  computations. It is found that the rate of accretion of the angular
  momentum in three-dimensional flows is about 5 times smaller than in
  the two-dimensional cases. The effect that this finding has on the
  modeling of wind-fed binary X-ray sources is discussed. It is concluded
  that only three-dimensional calculations can give a reliable answer
  to the question of angular momentum transfer to the neutron star.

---------------------------------------------------------
Title: A Model for Quiescent Solar Prominences with Normal Polarity
Authors: Hood, A. W.; Anzer, U.
1989HvaOB..13..281H    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: A Three-Dimensional Model for Solar Prominences
Authors: Demoulin, P.; Priest, E. R.; Anzer, U.
1989HvaOB..13..253D    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Structure and equilibrium of prominences
Authors: Anzer, U.
1989ASSL..150..143A    Altcode: 1988dsqs.work..143A; 1989dsqs.work..143A
  The existing models for magnetohydrostatic equilibrium of quiescent
  prominences are presented and critically discussed. Also considered
  is the question of how the energy balance can be achieved in these
  prominences. The main emphasis is on recent developments in these
  areas of research.

---------------------------------------------------------
Title: Thermal Condensations in Coronal Magnetic Fields
Authors: Hood, A.; Anzer, U.
1988SoPh..115...61H    Altcode:
  Conditions under which cool condensations can form in the solar corona
  are investigated using the powerful phase plane method to analyse the
  energy and hydrostatic balance equations. The importance of the phase
  plane approach is that the conclusions deduced are not sensitive to
  the actual choice of boundary conditions adopted which only determine
  the actual contour. The importance of heating variations and area
  divergence are studied as well as the influence of gravity for their
  effect on the formation of cool condensations. The cool temperature
  at which optically thin radiation and heating balance is important
  and the links with other cool solutions are mentioned.

---------------------------------------------------------
Title: Structure and equilibrium of prominences.
Authors: Anzer, U.
1988dssp.conf...99A    Altcode:
  The existing models for magnetohydrostatic equilibrium of quiescent
  prominences are presented and critically discussed. The author
  also investigates how the energy balance can be achieved in these
  prominences. The emphasis of this review is on the recent developments
  in these areas of research.

---------------------------------------------------------
Title: The influence of external magnetic fields on the structure
    of thin accretion disks.
Authors: Anzer, U.; Boerner, G.; Meyer-Hofmeister, E.
1987A&A...188...85A    Altcode:
  The internal structure of thin accretion disks is studied for the case
  where strong outside magnetic fields interact with these disks. Such
  configurations are expected to occur in close binary X-ray pulsars such
  as Her X-1. The authors find that the magnetic pressure exerted on the
  disk has two main effects: the vertical disk structure shows a density
  increase towards the interface between disk and magnetosphere; and the
  thickness of the disk decreases more rapidly as one approaches the inner
  edge of the disk. The second effect gives a stronger irradiation of
  the disk surface close to the inner edge and this results in a higher
  surface temperature.

---------------------------------------------------------
Title: The stability of line tied force-free cylindrical arcades:
    Is an active region filament a requirement for a two-ribbon flare?
Authors: Hood, A.; Anzer, U.
1987SoPh..111..333H    Altcode:
  The MHD stability of force-free, cylindrical arcades is investigated,
  including the stabilising effect of photospheric line tying. It is found
  that a wide variety of fields are stable. This suggests that either a
  departure from a force free equilibrium or suppression of line tying
  is necessary if a two-ribbon flare is to be triggered. It is postulated
  that in both circumstances, the existence of an active region filament
  is an essential preflare requirement for a two-ribbon flare.

---------------------------------------------------------
Title: Disk formation at the magnetosphere of wind-fed pulsars :
    applicationto VELA X-1.
Authors: Boerner, G.; Hayakawa, S.; Nagase, F.; Anzer, U.
1987A&A...182...63B    Altcode:
  The disk formation in a wind-fed, rotating, accreting neutron
  star is considered in view of the fact that the angular momentum
  transfer by wind accretion is too small to account for large rates
  of spin-up and spin-down as observed. Under the assumption that the
  closed magnetosphere extends to the corotation radius it is shown
  that a disk will form through the interaction of the spherically
  accreting matter with the rotating magnetosphere. Long term spin-up and
  spin-down episodes then become possible due to the difference between
  the accretion torque transmitted by the disk and the deceleration by
  the accretion at the magnetosphere surface. Large rates of short-term
  pulse period change are attributed to the change in the accretion
  torque transmitted by the disk. Application of this model to the X-ray
  source Vela X-1 requires a large magnetic moment μ ≡ 10<SUP>32</SUP>
  Gauss cm<SUP>3</SUP>, but once the high value for the magnetic field
  (10<SUP>13</SUP> Gauss ⪉ B ⪉ 10<SUP>14</SUP> Gauss) is accepted,
  a variety of observations fit well into the picture.

---------------------------------------------------------
Title: Numerical studies of wind accretion.
Authors: Anzer, U.; Boerner, G.; Monaghan, J. J.
1987A&A...176..235A    Altcode:
  Wind accretion from a companion star is assumed to be the power
  source for wide X-ray binaries. These winds will in general have
  spatial variations both in density and in the velocity vector. The
  authors have performed 2-dimensional numerical computations of such
  inhomogeneous wind flows to obtain estimates on the amount of angular
  momentum accreted for a given gradient of the velocity vector. They
  find that the angular momentum flux is about a factor 5 smaller than
  the previous estimates. This means that there is not enough angular
  momentum transferred to the neutron star to explain, for example,
  the long term period changes of Vela X-1. This leads the authors to
  propose a different mechanism for the spin-up and spin-down of sources
  of the type of Vela X-1. They outline briefly the physical features
  of such a model.

---------------------------------------------------------
Title: The influence of external magnetic fields on the structure
    of thin accretion disks.
Authors: Anzer, U.; Börner, G.; Meyer-Hofmeister, E.
1987imfo.work..203A    Altcode:
  There is a generally accepted picture of many binary X-ray sources
  wherein a rotating magnetized neutron star accretes matter from
  a surrounding disk of plasma. As the accreting matter approaches
  the rotating neutron star it is more and more influenced by the
  stellar magnetic field until eventually its motion is dominated by
  the field. Finally the plasma will flow along the field lines towards
  the surface of the neutron star. The equilibrium structure of a thin
  accretion disk subjected to the pressure of an external magnetic field
  is described.

---------------------------------------------------------
Title: Stability of Magnetic Arcades
Authors: Anzer, U.; Hood, A. W.
1987rfsm.conf..248A    Altcode:
  The authors conclude that sheared force-free arcades cannot become
  unstable and produce solar flares. They therefore predict that
  two-ribbon flares must always be associated with extended solar
  prominences.

---------------------------------------------------------
Title: Structure and Equilibrium of Prominences
Authors: Anzer, U.
1987dssp.work...99A    Altcode: 1987ASSL..150...99A
  No abstract at ADS

---------------------------------------------------------
Title: The influence of external magnetic fields on the structure
    of thin accretion disks.
Authors: Anzer, U.; Börner, G.; Meyer-Hofmeister, E.
1987MPARp.282.....A    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Modelling of the magnetic field of solar prominences.
Authors: Anzer, U.
1987ppcs.work...61A    Altcode:
  Measurements of magnetic fields with closed structures in quiescent
  prominences are discussed. It is shown that it is not possible to
  construct simple equilibrium models for quiescent prominences of the
  Kuperus-Raadu type. An open-field example is considered, and it is
  concluded that at present there exists no theoretical equililbrium
  model of the Kuperus-Raadu type which is consistent with observations.

---------------------------------------------------------
Title: Numerical studies of wind accretion.
Authors: Anzer, U.; Börner, G.; Monaghan, J. J.
1986MPARp.230.....A    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Interaction of the Accretion Disk with the Magnetosphere of
    a Rotating Neutron Star
Authors: Anzer, U.; Borner, G.
1986ppm..conf..101A    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: The global structure of magnetic fields which support quiescent
    prominences
Authors: Anzer, U.
1985svmf.nasa..101A    Altcode:
  Magnetic fields in quiescent prominences were observed, but only
  recently has it become possible to measure the full magnetic field
  vector. The component of the field along the line of sight, B (parallel)
  can be uniquely determined, whereas for the component perpendicular
  to the line of sight B (perpendicular) and -B (perpendicular)
  are indistinguishable. An ambiguity remains in the actual magnetic
  field vector, in particular with respect to its orientation relative
  to the prominence axis. A sample of more than 100 prominences were
  studied. A more detailed analysis of 10 prominences are presented,
  and then set these prominence fields into relation to the underlying
  photospheric fields. It is found from statistical analysis of several
  hundred prominences that in 25% of the cases the field penetrates
  the prominence directly, whereas in 75% the field orientation in the
  prominence is reversed.

---------------------------------------------------------
Title: Remarks on the Magnetic Support of Quiescent Prominences
Authors: Anzer, U.; Priest, E.
1985SoPh...95..263A    Altcode:
  The development of magnetic field structures which can
  lead to prominence configurations of the Kuperus-Raadu type is
  discussed. Starting from streamer type configurations and preserving the
  total current in the system we find that simple two-dimensional static
  configurations lead to prominences which in general lie systematically
  much lower than the heights found from observations. We therefore
  conclude that either more complex field configurations are needed to
  explain the recent observations by Leroy et al. (1983) or the initial
  configurations must be very special.

---------------------------------------------------------
Title: The global structure of magnetic fields which support quiescent
    prominences.
Authors: Anzer, U.
1985NASCP2374..101A    Altcode:
  The author reviews and discusses models of magnetic field configurations
  in prominences.

---------------------------------------------------------
Title: Theoretical modelling of inhomogeneous fields in the
    chromosphere.
Authors: Anzer, U.; Galloway, D. J.
1985cdm..proc..199A    Altcode:
  Theoretical models of the magnetic field structure above a photosphere
  with magnetic flux tubes are constructed, on the hypotheses that
  the field is either current-free or is governed by the force-free
  equation j = αB, with α constant. The level where the magnetic
  pressure becomes equal to the ambient gas pressure is calculated,
  and is shown to depend very little on which of the above hypotheses
  is adopted. The resulting levels are in agreement with the "canopy
  heights" given by Giovanelli (1980) and Giovanelli and Jones (1982)
  for areas around active regions, but are higher than the results
  for the quiet, unipolar regions in Giovanelli and Jones (1983). The
  calculations suggest there are large regions of the low to middle
  quiet chromosphere that require non-magnetic heating mechanisms.

---------------------------------------------------------
Title: Some aspects of the angular momentum transfer between an
    accretion disk and a rotating, magnetic neutron star
Authors: Anzer, U.; Boerner, G.
1984AdSpR...3j.315A    Altcode: 1984AdSpR...3..315A
  No abstract at ADS

---------------------------------------------------------
Title: Remarks on the magnetic support of quiescent prominences.
Authors: Anzer, U.; Priest, E.
1984MPARp.157.....A    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Some Aspects of the Angular Momentum Transfer Between an
    Accretion Disk and a Rotating Magnetic Neutron Star
Authors: Anzer, U.; Borner, G.
1984heac.conf..315A    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Accretion onto rotating, magnetic neutron stars : the inner
    edge of the disk.
Authors: Anzer, U.; Boerner, G.
1983A&A...122...73A    Altcode:
  The surface of an accretion disk in a rotating neutron star's magnetic
  field is subject to the Kelvin-Helmholtz instability induced by
  the velocity difference of the rigidly rotating magnetosphere and
  the Keplerian disk. This instability is analysed in a simplified
  geometry. It is shown that a large part of the disk surface will become
  unstable, leading to a turbulent diffusion of the disk plasma into
  the magnetosphere. The resulting exchange of angular momentum between
  the neutron star and the accreting matter is described. The present
  model of a magnetic dipole axis perpendicular to the rotation axis of
  the neutron star is compared to the model of an aligned rotator. The
  observational consequences with respect to the rotational state of
  pulsating X-ray sources are discussed.

---------------------------------------------------------
Title: A model for the magnetic field above supergranules
Authors: Anzer, U.; Galloway, D. J.
1983MNRAS.203..637A    Altcode:
  A model is provided for the inhomogeneous magnetic field structure above
  a stellar photosphere where the field is concentrated in intense tubes
  at the downflow regions of a convection pattern. By finding where the
  magnetic energy is strong or weak compared with the local thermal energy
  of the gas, the relative importance of magnetic and non-magnetic heating
  mechanisms can be estimated for those regions where the principal
  radiative losses occur in solar or stellar chromospheres. For the
  quiet Sun, slightly over half of the chromospheric emission comes
  from regions which are essentially non-magnetic. For other stars,
  the calculations yield a simple working rule which suggests that most
  late-type stars with fields strong enough to be directly observable
  will have magnetically dominated chromospheres.

---------------------------------------------------------
Title: The magnetic field configuration in solar and stellar
    chromospheres
Authors: Anzer, U.; Galloway, D. J.
1983IAUS..102..339A    Altcode:
  Calculations are presented for the inhomogeneous magnetic field
  structure above a stellar photosphere which has magnetic flux tubes
  located at the downdraughts of its supergranulation pattern. Regions
  can be delineated where the ambient magnetic energy density is large
  or small compared with the thermal energy density derived from a model
  atmosphere. This enables the relative importance of magnetic versus
  non-magnetic heating mechanisms to be assessed. For the quiet Sun,
  over half the chromospheric emission must be supplied non-magnetically,
  whilst the network and active regions require a magnetic supply. For
  other late-type stars, a simple working rule suggests that when
  the magnetic field is strong enough to be directly observable, the
  chromosphere will be magnetically dominated.

---------------------------------------------------------
Title: Interaction of accretion disks and rotating magnetic neutron
    stars.
Authors: Anzer, U.; Boerner, G.
1983heac.book..294A    Altcode:
  Consideration is given to some theoretical aspects of the interaction of
  an accretion disk and a rotating magnetic star. The principle numerical
  models of the problem are analyzed with respect to parameterizations
  of the angular momentum exchange between the accretion disk and the
  magnetic neutron star. On the basis of the analysis, a detailed
  quantitative model is proposed. In the model, Kelvin-Helmholtz
  instability leads to turbulent diffusion of disk matter onto the
  magnetic lines of the neutron star near the region of corotation. The
  balance and acceleration of the stars are calculated and the angular
  momentum exchange is obtained. The model calculations are given in
  a table. Emphasis is given to the need for greater generalization in
  current numerical models of the problem in order to account for both
  Kelvin-Helmholtz and Rayleigh-Taylor MHD instabilities.

---------------------------------------------------------
Title: Accretion onto rotating magnetic neutron stars: the inner
    edge of the disk.
Authors: Anzer, U.; Börner, G.
1982ans..conf..155A    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Magnetic Reconnection and Coronal Transients
Authors: Anzer, U.; Pneuman, G. W.
1982SoPh...79..129A    Altcode:
  Every two-ribbon flare observed during the Skylab period produced an
  observable coronal transient, provided the flare occurred close enough
  to the limb. The model presented here treats these two events as a
  combined process. Transients that occur without flares are believed
  to involve magnetic fields that are too weak to produce significant
  chromospheric emission. Adopting the hypothesis that the rising
  flare loop systems observed during two-ribbon flares are exhibiting
  magnetic reconnection, a model of a coronal transient is proposed which
  incorporates this reconnection process as the driving force. When two
  oppositely directed field lines reconnect a lower loop is created rooted
  to the solar surface (the flare loop) and an upper disconnected loop is
  produced which is free to rise. The magnetic flux of these upper loops
  is proposed as the driver for the transient. The force is produced by
  the increase in magnetic pressure under the filament and transient.

---------------------------------------------------------
Title: How disk accretion affects a rotating dipole
Authors: Anzer, U.; Börner, G.; Zhou, Y. Y.
1982MitAG..55...28A    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Kelvin-Helmholtz Instabilities at the Interface Between an
    Accretion Disk and the Magnetosphere of a Neutron Star
Authors: Anzer, U.; Börner, G.
1982ZNatA..37..723A    Altcode: 1982ZNaT...37..723A
  No abstract at ADS

---------------------------------------------------------
Title: Accretion by neutron stars - Accretion disk and rotating
    magnetic field
Authors: Anzer, U.; Boerner, G.
1980A&A....83..133A    Altcode:
  The paper studies the interaction of a thin Keplerian accretion disk
  with the magnetosphere of a rotating neutron star. The neutron star's
  axis of rotation is assumed to be perpendicular to and the magnetic
  dipole axis parallel to the disk plane. In such a configuration the
  disk can penetrate diamagnetically into the magnetosphere. The velocity
  difference between the disk material and the magnetosphere leads to
  a Kelvin-Helmholtz instability of the interface. This instability
  can grow to large amplitudes only within a narrow ring around the
  corotation radius. It can give rise to turbulent diffusion of the disk
  material into the magnetosphere. Part of this material will fall onto
  the neutron star, the rest will be flung out of the system. This can
  lead to an approximate balance between braking and acceleration of the
  neutron star. Application of the model to the pulsating X-ray source
  Her X-1 gives a natural explanation of the observed temporal variation
  of the pulse period.

---------------------------------------------------------
Title: The preflare state
Authors: van Hoven, G.; Barbosa, D. D.; Birn, J.; Cheng, C. -C.;
   Hansen, R. T.; Jackson, B. V.; Martin, S. F.; McIntosh, P. S.;
   Nakagawa, Y.; Anzer, U.
1980sfsl.work...17V    Altcode: 1980sofl.symp...17V
  The accumulation, storage and irreversible release of the free
  energy necessary for a solar flare are discussed on the basis of data
  obtained from the Apollo Telescope Mount on Skylab and other pertinent
  sources. Skylab and OSO 7 observations of possible flare precursors
  and flare evolution are presented, and the evolution of the flare of
  Sept. 5, 1973, the most completely observed flare of the Skylab program,
  is described in detail, with account given to magnetic structures and
  H alpha radiation. Theories of the preflare state are then reviewed,
  with attention given to the force-free fields and coronal arcades,
  thermal and magnetic structures and the MHD stability of coronal loops.

---------------------------------------------------------
Title: MHD aspects of coronal transients
Authors: Anzer, U.
1980IAUS...91..263A    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Instabilities of accretion disk - magnetosphere interfaces.
Authors: Anzer, U.; Boerner, G.
1979ESASP.148..259A    Altcode: 1979mbl..rept..259A
  Configurations which consist of a Keplerian accretion disk and
  a magnetosphere with solid rotation are investigated. Because of
  the velocity difference between disk and magnetosphere the boundary
  between the two is unstable to the Kelvin-Helmholtz instability. This
  instability is strongest within a ring around the radius of
  corotation. It leads to turbulent diffusion of disk material into the
  magnetosphere, and thus gives a sufficiently high accretion rate.

---------------------------------------------------------
Title: Interaction of accretion disk and rotating magnetic field of
    a neutron star.
Authors: Anzer, U.; Boerner, G.
1979ESASP.148..263A    Altcode: 1979mbl..rept..263A
  Utilizing the instabilities of the boundary between disk and
  magnetosphere, a model for the flow of disk material into the neutron
  star's magnetosphere is constructed. It is shown that within a thin
  ring around the corotation radius, gas flows over. The gas is partly
  accelerated towards the neutron star producing the accretion partly
  outwards. In terms of this model, certain observed properties of
  pulsating X-ray sources are explained.

---------------------------------------------------------
Title: Mass flow in loop type coronal transients.
Authors: Anzer, U.; Poland, A. I.
1979SoPh...61...95A    Altcode:
  The white light coronagraph on Skylab observed many loop type coronal
  transients. These loops travel through the coronagraph's field of view
  (2-6R<SUB>⊙</SUB>) over a period of a few hours, after which the legs
  of the loops usually remain visible for a few days. In this paper we
  investigate the temporal changes in density and mass per unit length
  measured along the legs of such loops during the several days after
  the initial eruption. Examination of 8 transients shows that the mass
  and density in the legs decrease during the few hours after the top of
  the loop has travelled beyond the coronagraph's field of view. The mass
  and density then increase slowly, during the next one half to one day,
  then decrease again over approximately the same period. These changes
  are generally shown to be too rapid to be explained by solar rotation,
  indicating that the transient legs have a lifetime of only a few days.

---------------------------------------------------------
Title: Models of Structure and Dynamics of Prominences.
Authors: Anzer, U.
1979phsp.coll..322A    Altcode: 1979IAUCo..44..322A; 1979phsp.conf..322A
  The degree and direction of the linear polarization of the helium D3
  lines in quiescent prominences is examined. Three types of prominence
  models including the Kippenhahn-Schlueter, Kuperus-Raadu, and Matville
  models, each having current flows inside of them that give rise to
  Lorentz forces, keeping the material from falling into the sun, are
  described in detail. The main emphasis of measurements of the magnetic
  force field centered on the Hanle and Zeeman effects as well as the
  motions and fine structures of prominences. Results showed that it is
  possible to obtain information on the field surrounding the prominences
  from polarization measurements in the radio spectrum.

---------------------------------------------------------
Title: Discussion
Authors: Anzer, U.; Maltby, P.; Spicer, D. S.
1979phsp.coll..348A    Altcode: 1979IAUCo..44..348A
  No abstract at ADS

---------------------------------------------------------
Title: Discussion
Authors: Anzer, U.; Raadu, M. A.; Rompolt, B.; Rust, D. M.; Sheeley,
   N.; Spicer, D. S.
1979phsp.coll..171A    Altcode: 1979IAUCo..44..171A
  No abstract at ADS

---------------------------------------------------------
Title: Discussion
Authors: Acton, L. W.; Anzer, U.; Engvold, O.; Martin, S. F.; Pneuman,
   G. W.; Rust, D. M.; Tandberg-Hanssen, E.; Zirin, H.
1979phsp.coll..164A    Altcode: 1979IAUCo..44..164A
  No abstract at ADS

---------------------------------------------------------
Title: Discussion
Authors: Anzer, U.; Engvold, O.; Spicer, D. S.; van Tend, W.; Zirin, H.
1979phsp.coll..331A    Altcode: 1979IAUCo..44..331A
  No abstract at ADS

---------------------------------------------------------
Title: Discussion
Authors: Anzer, U.; Chiuderi-Drago, F.; Kundu, M. R.; Leroy, J. L.;
   Malville, J.; Rompolt, B.; Sheeley, N.; Stenflo, J.; Tandberg-Hanssen,
   E.; Öhman, Y.
1979phsp.coll...77A    Altcode: 1979IAUCo..44...77A
  No abstract at ADS

---------------------------------------------------------
Title: Can coronal loop transients be driven magnetically?
Authors: Anzer, U.
1978SoPh...57..111A    Altcode:
  In this note we investigate the possibility of magnetic driving of loop
  transients. The action of local magnetic forces to balance gravity in a
  coasting loop and to confine the loop has been proposed by Mouschovias
  and Poland (1977). In this paper we use similar configurations but
  deal with the global field structure and present models which show both
  the initial phase of large acceleration and the later phase of almost
  constant velocity. We use very simple one-dimensional models consisting
  of a ring current which is subjected to gravitational attraction. The
  velocity curves calculated for these models are in good agreement with
  the observations. Therefore we conclude that if such ring currents
  can be produced fast enough in the solar corona, they are capable of
  driving the loop transients observed in the ATM white light coronagraph.

---------------------------------------------------------
Title: Accretion disk and rotating magnetic field of a neutron star.
Authors: Börner, G.; Anzer, U.
1978sss..meet..B16B    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: X-ray Stars: Disc Accretion onto a Rotating Magnetized
    Neutron Star
Authors: Anzer, U.; Boerner, G.
1978MitAG..43..274A    Altcode:
  The interaction between a disk and a neutron star's magnetic field
  is analyzed. It is assumed that the neutron star has a strong dipole
  field with its axis in the plane of the disk and perpendicular to the
  rotation axis, and a reason for the disk to behave like a diamagnetic
  material in the stars's magnetic field is given. The role of the
  Kelvin-Helmholtz instability in the interaction of disk matter and
  magnetic field is examined, and some implications for the disk accretion
  model are discussed.

---------------------------------------------------------
Title: Shock waves in stellar wind accretion and gamma -bursts.
Authors: Anzer, U.; Boerner, G.; Meszaros, P.
1976A&A....50..305A    Altcode:
  A model of cosmic gamma-ray bursts is proposed, involving spherical
  accretion on compact objects from the stellar wind of a companion
  star. The gamma-bursts arise when occasional flares in the companion
  drive shocks in the wind, which then produce a short increase in the
  accretion rate on the compact object. In the interval between flares,
  the steady accretion from the wind leads to an X-ray source behavior
  compatible with that of observed galactic X-ray sources. The model is
  flexible enough to reproduce the large range of observed gamma-ray burst
  characteristics, including luminosities, timescales and approximate
  spectra. Specifically, it can explain the recently suggested possibility
  that Cygnus X-1 is responsible for some of the gamma-ray events,
  as well as the recently reported orbit-modulated absorption features.

---------------------------------------------------------
Title: Bremsstrahlung and the Spectra of Cosmic Gamma Bursts
Authors: Anzer, U.; Boerner, G.
1976MitAG..38..121A    Altcode:
  The possibility had been considered by Anzer and Boerner (1975)
  that cosmic gamma-bursts are bremsstrahlung which is produced by the
  interaction of a mildly relativistic beam of electrons with the protons
  of a neutral plasma. An investigation concerning an occurrence of a
  thermal bremsstrahlung is conducted, taking into account a comparison
  between an observed spectrum reported by Metzger et al. (1974) and
  calculated spectra of thermal bremsstrahlung.

---------------------------------------------------------
Title: Shock waves in stellar wind accretion and gamma
    -bursts. Bremsstrahlung and the spectra of cosmic gamma bursts.
Authors: Anzer, U.; Boerner, G.; Meszaros, P.
1976swsw.book.....A    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Why Syrovatskii's mechanism of dynamic dissipation of magnetic
    fields does not work.
Authors: Anzer, U.
1976str..book..375A    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Why Syrovatskii's mechanism of dynamic dissipation of magnetic
    fields does not work
Authors: Anzer, U.
1976CoSka...6..375A    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: A possible mechanism for cosmic gamma ray bursts.
Authors: Anzer, U.; Boerner, G.
1975A&A....40..123A    Altcode:
  The recently discovered cosmic gamma-ray bursts can be explained
  by the bremsstrahlung of a beam of relativistic electrons hitting a
  region of high proton density. Spectra are computed, and estimates on
  the particle densities and on the geometrical dimensions are derived
  from the observations. The question of associated optical emission is
  also discussed.

---------------------------------------------------------
Title: Why Syrovatskii's Mechanism of Dynamic Dissipation of Magnetic
    Fields Does Not Work
Authors: Anzer, Ulrich
1973SoPh...30..459A    Altcode:
  Syrovatskii's mechanism of `dynamic dissipation of magnetic field' is
  reinvestigated. In order to have this kind of `dynamic dissipation'
  at a neutral line the ratio of current density to particle density
  must exceed a certain critical value. For conditions in the solar
  atmosphere near sunspots, this value can only be reached by a mechanism
  which produces a very large compression of the magnetic field as well
  as an extreme rarefaction of the density. Syrovatskii claims that his
  mechanism provides both these features. His enormous field compression,
  however, can only be obtained if one neglects the restoring Lorentz
  force (e.g. in Syrovatskii's model the compressed field near the
  neutral line is about one order of magnitude larger than the field of
  the sunspots which generates it). The second effect, i.e. the large
  plasma rarefaction around the neutral line, also is not real. This
  rarefaction is due to the particular flow field of Syrovatskii's
  model which allows for a free reconnection of the field lines across
  the neutral line; the magnetic field is treated like a vacuum field,
  the effects of the field accumulation near the neutral line being
  neglected. The aim of the present paper is to show how more realistic
  models modify Syrovatskii's results. Our numerical calculations lead to
  a maximum current to density ratio which is a factor of 10<SUP>6</SUP>
  smaller than the one obtained by Syrovatskii. Therefore one has to
  conclude that in the solar atmosphere one cannot produce in the way
  described by Syrovatskii the configurations which are necessary for
  `dynamic dissipation'.

---------------------------------------------------------
Title: On a cinematographic observation of the tail of comet
    Kohoutek 1973f.
Authors: Anzer, U.; Jockers, K.; Schmidt, H. U.
1973JASWA..25...14A    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Zur kinematographischen Beobachtung des Schweifs des Kometen
    Kohoutek 1973f.
Authors: Anzer, U.; Jockers, K.; Schmidt, H. U.
1973S&W....12..293A    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Kritik an Syrovatskiis Mechanismus der dynamischen Dissipation
    von Magnetfeldern
Authors: Anzer, U.
1973MitAG..32..171A    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: A Method to Calculate Electric Currents in Quiescent
    Prominences
Authors: Anzer, Ulrich
1972SoPh...24..324A    Altcode:
  A 2-dimensional model of the magnetic field associated with
  quiescent prominences is presented. The coronal field is assumed to be
  current-free, currents are only allowed in the photosphere and inside
  the prominence. The prominence is taken to be infinitely thin. For this
  model a method is given to calculate the field configuration from the
  observed normal component of the field both in the photosphere and
  the prominence. The normal field components are inferred from disc
  observations and Hα limb observations. The sheet currents inside the
  prominence are calculated and the resulting Lorentz force is compared
  with the gravitational force. Within the range of uncertainty in the
  total hydrogen density of quiescent prominences it is possible to give
  models where the gravity is balanced by the Lorentz force.

---------------------------------------------------------
Title: Energy Balance in Cool Quiescent Prominences
Authors: Poland, A.; Anzer, U.
1971SoPh...19..401P    Altcode:
  The energy balance for cool quiescent prominences is examined using
  a 6000 km, 6000 K isothermal slab model prominence with a density
  gradient dictated by a modified Kippenhahn-Schlüter model. The
  model is irradiated from both sides by the coronal, chromospheric,
  and photospheric radiation fields. The radiative transfer problem is
  solved in detail for the Lyman continuum and Hα to determine the net
  radiative energy loss for hydrogen. An estimate of the energy loss for
  Ca II H and K indicates that this source of energy loss is unimportant
  when compared with the hydrogen radiation. The radiative energy loss
  is easily balanced by the conductive energy gain from the corona.

---------------------------------------------------------
Title: Energy balance in quiescent prominences.
Authors: Poland, A.; Anzer, U.
1971BAAS....3..353P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: On the Orientation of Magnetic Fields in Quiescent Prominences
Authors: Anzer, U.; Tandberg-Hanssen, E.
1971IAUS...43..656A    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: The Orientation of Magnetic Fields in Quiescent Prominences
Authors: Tandberg-Hanssen, E.; Anzer, Ulrich
1970SoPh...15..158T    Altcode:
  We have measured the longitudinal component, B∥, of the magnetic field
  in quiescent prominences and obtained a relationship between B∥ and
  θ, where θ is the angle between the long axis of the prominence and
  the north-south direction on the sun. From this relationship we deduce
  a distribution function for the magnetic field vector in quiescent
  prominences in terms of the angle α between the field and the long
  axis of the prominence. The mean angle, α, for our data is small,
  ∼ - 15°, indicating that the magnetic field traverses quiescent
  prominences under a small, but finite angle.

---------------------------------------------------------
Title: A Model for Quiescent Prominences with Helical Structure
Authors: Anzer, Ulrich; Tandberg-Hanssen, E.
1970SoPh...11...61A    Altcode:
  We present a model for quiescent prominences with helical structure. The
  model is described by two magnetic fields, one produced by photospheric
  or subphotospheric currents, the other due to currents along the
  cylindrical model prominence.

---------------------------------------------------------
Title: Stability Analysis of the Kippenhahn-Schlüter Model of
    Solar Filaments
Authors: Anzer, U.
1969SoPh....8...37A    Altcode:
  In this paper the stability of the Kippenhahn-Schlüter model of solar
  filaments against arbitrary perturbations is investigated. The problem
  is treated in the MHD approximation and a modification of the energy
  principle of Bernstein et al. is used. Two necessary and sufficient
  stability conditions are found: (a) [B<SUB>z</SUB>] dB<SUB>x</SUB>/dz
  ≧ 0 and (b) B<SUB>x</SUB> d[B<SUB>z</SUB>]/dz ≦ 0. Condition
  (a), in the limit of small currents, leads to the condition already
  discussed by Kippenhahn and Schlüter; condition (b) requires that
  the current density in the stable filament decreases with height.

---------------------------------------------------------
Title: On the Stability of Solar Filaments
Authors: Anzer, Ulrich
1969BAAS....1R.271A    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Remarks on my Paper about Force-Free Magnetic Fields and
    Solar Flares
Authors: Anzer, Ulrich
1968SoPh....4..101A    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: The Stability of Force-Free Magnetic Fields with Cylindrical
    Symmetry in the Context of Solar Flares
Authors: Anzer, Ulrich
1968SoPh....3..298A    Altcode:
  The problem of the accumulation and storage of the energy released in
  solar flares is discussed; it is proposed that convective energy of the
  photosphere is transformed into magnetic energy of the chromosphere
  and corona. The consequences of a large ratio of magnetic pressure
  to gas pressure are investigated. In this case the field must be
  approximately force-free. The only suitable force-free fields which
  allow an analytical treatment are those of cylindrical symmetry. The
  stability of these fields is studied with the energy principle. It is
  shown that they are always unstable due to kink type instabilities. The
  shape of the unstable perturbations is described in detail and an
  upper limit for their amplitude is estimated. The consequences for
  the proposed mechanism of energy storage are briefly discussed.