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Author name code: utz
ADS astronomy entries on 2022-09-14
author:"Utz, Dominik"
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Title: The Solar Activity Monitor Network - SAMNet
Authors: Erdélyi, Robertus; Korsós, Marianna B.; Huang, Xin; Yang,
Yong; Pizzey, Danielle; Wrathmall, Steven A.; Hughes, Ifan G.;
Dyer, Martin J.; Dhillon, Vikram S.; Belucz, Bernadett; Brajša,
Roman; Chatterjee, Piyali; Cheng, Xuewu; Deng, Yuanyong; Domínguez,
Santiago Vargas; Joya, Raúl; Gömöry, Peter; Gyenge, Norbert G.;
Hanslmeier, Arnold; Kucera, Ales; Kuridze, David; Li, Faquan; Liu,
Zhong; Xu, Long; Mathioudakis, Mihalis; Matthews, Sarah; McAteer,
James R. T.; Pevtsov, Alexei A.; Pötzi, Werner; Romano, Paolo; Shen,
Jinhua; Temesváry, János; Tlatov, Andrey G.; Triana, Charles; Utz,
Dominik; Veronig, Astrid M.; Wang, Yuming; Yan, Yihua; Zaqarashvili,
Teimuraz; Zuccarello, Francesca
2022JSWSC..12....2E Altcode:
The Solar Activity Magnetic Monitor (SAMM) Network (SAMNet) is a
future UK-led international network of ground-based solar telescope
stations. SAMNet, at its full capacity, will continuously monitor
the Sun's intensity, magnetic, and Doppler velocity fields at
multiple heights in the solar atmosphere (from photosphere to upper
chromosphere). Each SAMM sentinel will be equipped with a cluster of
identical telescopes each with a different magneto-optical filter (MOFs)
to take observations in K I, Na D, and Ca I spectral bands. A subset
of SAMM stations will have white-light coronagraphs and emission line
coronal spectropolarimeters. The objectives of SAMNet are to provide
observational data for space weather research and forecast. The goal
is to achieve an operationally sufficient lead time of e.g., flare
warning of 2-8 h and provide many sought-after continuous synoptic
maps (e.g., LoS magnetic and velocity fields, intensity) of the lower
solar atmosphere with a spatial resolution limited only by seeing or
diffraction limit, and with a cadence of 10 min. The individual SAMM
sentinels will be connected to their master HQ hub where data received
from all the slave stations will be automatically processed and flare
warning issued up to 26 h in advance.
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Title: Observational evidence for two-component distributions
describing solar magnetic bright points
Authors: Berrios Saavedra, Gerardine; Utz, Dominik; Vargas Domínguez,
Santiago; Campos Rozo, José Iván; González Manrique, Sergio Javier;
Gömöry, Peter; Kuckein, Christoph; Balthasar, Horst; Zelina, Peter
2022A&A...657A..79B Altcode: 2021arXiv211012404B
Context. High-resolution observations of the solar photosphere reveal
the presence of fine structures, in particular the so-called Magnetic
Bright Points (MBPs), which are small-scale features associated with
strong magnetic field regions of the order of kilogauss (kG). It
is especially relevant to study these magnetic elements, which are
extensively detected in all moments during the solar cycle, in order to
establish their contribution to the behavior of the solar atmosphere,
and ultimately a plausible role within the coronal heating problem. <BR
/> Aims: Characterisation of size and velocity distributions of MBPs in
the solar photosphere in two different datasets of quiet Sun images
acquired with high-resolution solar instruments i.e. Solar Optical
Telescope SOT/Hinode and the High-resolution Fast Imager HiFI/GREGOR,
in the G-band (4308 Å). <BR /> Methods: In order to detect the
MBPs, an automatic segmentation and identification algorithm is
used. Next, the identified features were tracked to measure their
proper motions. Finally, a statistical analysis of hundreds of MBPs is
carried out, generating histograms for areas, diameters and horizontal
velocities. <BR /> Results: This work establishes that areas and
diameters of MBPs display log-normal distributions that are well-fitted
by two different components, whereas the velocity vector components
follow Gaussians and the vector magnitude a Rayleigh distribution
revealing again for all vector elements a two component composition. <BR
/> Conclusions: The results can be interpreted as due to the presence of
two different populations of MBPs in the solar photosphere one likely
related to stronger network magnetic flux elements and the other one
to weaker intranetwork flux elemens. In particular this work concludes
on the effect of the different spatial resolution of GREGOR and Hinode
telescopes, affecting detections and average values.
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Title: The Dark Universe is not invisible
Authors: Zioutas, K.; Anastassopoulos, V.; Argiriou, A.; Cantatore,
G.; Cetin, S. A.; Gardikiotis, A.; Hoffmann, D. H. H.; Hofmann, S.;
Karuza, M.; Kryemadhi, A.; Maroudas, M.; Matteson, E. L.; Ozbozduman,
K.; Papaevangelou, T.; Perryman, M.; Semertzidis, Y. K.; Tsagris,
I.; Tsagri, M.; Tsiledakis, G.; Utz, D.; Valachovic, E. L.
2021arXiv210811647Z Altcode:
Dark matter (DM) comes from long-range gravitational observations,
and it is considered as something that does not interact with ordinary
matter or emits light. However, also on much smaller scales, a number
of unexpected observations of the solar activity and the dynamic
Earth atmosphere might arise from DM contradicting the aforementioned
DM picture. Because, gravitational (self) focusing effects by the
Sun or its planets of streaming DM fit as the interpretation of the
otherwise puzzling 11-year solar cycle, the mysterious heating of the
solar corona, atmospheric transients, etc. Observationally driven, an
external impact by overlooked streaming invisible matter reconciles
the investigated mysterious behavior showing otherwise unexpected
planetary relationships; this is a signature for gravitational focusing
of streaming DM by the solar system bodies. Then, focusing of DM streams
could also occur in exoplanetary systems, suggesting for the first
time the carrying out of investigations by searching for the associated
stellar activity as a function of the exoplanetary orbital phases.
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Title: Evidence For Two-component Distributions Describing Magnetic
Bright Points In The Solar Photosphere
Authors: Vargas Domínguez, S.; Berrios Saavedra, G.; Utz, D.;
Campos Rozo, J. I.; González Manrique, S.; Gömöry, Peter; Kuckein,
Christoph; Balthasar, Horst; Zelina, Peter
2021AAS...23811310V Altcode:
High-resolution observations of the Sun reveal the presence of Magnetic
Bright Points (MBPs), which are small-scale features associated with
strong magnetic field regions, that are found all over the solar
photosphere. In this work, we characterize some physical properties
and dynamics of MBPs in a quiet Sun region by using time series of
images acquired with the High-resolution Fast Imager HiFI/GREGOR and
Solar Optical Telescope SOT/Hinode in the G-band (4308 Angstrom). An
automated segmentation algorithm is used to identify the MBPs and
track their evolution. The results show observational evidence for
two-component distributions of areas, diameters and velocities, that
can be interpreted as corresponding to different populations of MBPs.
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Title: Could Switchbacks Originate in the Lower Solar
Atmosphere? II. Propagation of Switchbacks in the Solar Corona
Authors: Magyar, Norbert; Utz, Dominik; Erdélyi, Robertus; Nakariakov,
Valery M.
2021ApJ...914....8M Altcode: 2021arXiv210410126M
The magnetic switchbacks observed recently by the Parker Solar Probe
have raised the question about their nature and origin. One of the
competing theories of their origin is the interchange reconnection
in the solar corona. In this scenario, switchbacks are generated at
the reconnection site between open and closed magnetic fields, and
are either advected by an upflow or propagate as waves into the solar
wind. In this paper we test the wave hypothesis, numerically modeling
the propagation of a switchback, modeled as an embedded Alfvén wave
packet of constant magnetic field magnitude, through the gravitationally
stratified solar corona with different degrees of background magnetic
field expansion. While switchbacks propagating in a uniform medium with
no gravity are relatively stable, as reported previously, we find that
gravitational stratification together with the expansion of the magnetic
field act in multiple ways to deform the switchbacks. These include WKB
effects, which depend on the degree of magnetic field expansion, and
also finite-amplitude effects, such as the symmetry breaking between
nonlinear advection and the Lorentz force. In a straight or radially
expanding magnetic field the propagating switchbacks unfold into waves
that cause minimal magnetic field deflections, while a super-radially
expanding magnetic field aids in maintaining strong deflections. Other
important effects are the mass uplift the propagating switchbacks
induce and the reconnection and drainage of plasmoids contained within
the switchbacks. In the Appendix, we examine a series of setups with
different switchback configurations and parameters, which broaden the
scope of our study.
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Title: Could Switchbacks Originate in the Lower Solar
Atmosphere? I. Formation Mechanisms of Switchbacks
Authors: Magyar, Norbert; Utz, Dominik; Erdélyi, Robertus; Nakariakov,
Valery M.
2021ApJ...911...75M Altcode: 2021arXiv210303726M
The recent rediscovery of magnetic field switchbacks or deflections
embedded in the solar wind flow by the Parker Solar Probe mission lead
to a huge interest in the modeling of the formation mechanisms and
origin of these switchbacks. Several scenarios for their generation were
put forth, ranging from lower solar atmospheric origins by reconnection,
to being a manifestation of turbulence in the solar wind, and so
on. Here we study some potential formation mechanisms of magnetic
switchbacks in the lower solar atmosphere, using three-dimensional
magnetohydrodynamic (MHD) numerical simulations. The model is that of an
intense flux tube in an open magnetic field region, aiming to represent
a magnetic bright point opening up to an open coronal magnetic field
structure, e.g., a coronal hole. The model is driven with different
plasma flows in the photosphere, such as a fast up-shooting jet,
as well as shearing flows generated by vortex motions or torsional
oscillations. In all scenarios considered, we witness the formation
of magnetic switchbacks in regions corresponding to chromospheric
heights. Therefore, photospheric plasma flows around the foot-points
of intense flux tubes appear to be suitable drivers for the formation
of magnetic switchbacks in the lower solar atmosphere. Nevertheless,
these switchbacks do not appear to be able to enter the coronal heights
of the simulation in the present model. In conclusion, based on the
presented simulations, switchbacks measured in the solar wind are
unlikely to originate from photospheric or chromospheric dynamics.
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Title: Magnetic Flux Emergence in a Coronal Hole
Authors: Palacios, Judith; Utz, Dominik; Hofmeister, Stefan; Krikova,
Kilian; Gömöry, Peter; Kuckein, Christoph; Denker, Carsten; Verma,
Meetu; González Manrique, Sergio Javier; Campos Rozo, Jose Iván;
Koza, Július; Temmer, Manuela; Veronig, Astrid; Diercke, Andrea;
Kontogiannis, Ioannis; Cid, Consuelo
2020SoPh..295...64P Altcode: 2020arXiv200611779P
A joint campaign of various space-borne and ground-based observatories,
comprising the Japanese Hinode mission (Hinode Observing Plan 338,
20 - 30 September 2017), the GREGOR solar telescope, and the Vacuum
Tower Telescope (VTT), investigated numerous targets such as pores,
sunspots, and coronal holes. In this study, we focus on the coronal
hole region target. On 24 September 2017, a very extended non-polar
coronal hole developed patches of flux emergence, which contributed
to the decrease of the overall area of the coronal hole. These flux
emergence patches erode the coronal hole and transform the area into a
more quiet-Sun-like area, whereby bipolar magnetic structures play an
important role. Conversely, flux cancellation leads to the reduction
of opposite-polarity magnetic fields and to an increase in the area
of the coronal hole.
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Title: Revisiting the building blocks of solar magnetic fields
by GREGOR
Authors: Utz, Dominik; Kuckein, Christoph; Campos Rozo, Jose Iván;
González Manrique, Sergio Javier; Balthasar, Horst; Gömöry,
Peter; Hernández, Judith Palacios; Denker, Carsten; Verma, Meetu;
Kontogiannis, Ioannis; Krikova, Kilian; Hofmeister, Stefan; Diercke,
Andrea
2020IAUS..354...38U Altcode:
The Sun is our dynamic host star due to its magnetic fields causing
plentiful of activity in its atmosphere. From high energetic flares
and coronal mass ejections (CMEs) to lower energetic phenomena such
as jets and fibrils. Thus, it is of crucial importance to learn about
formation and evolution of solar magnetic fields. These fields cover a
wide range of spatial and temporal scales, starting on the larger end
with active regions harbouring complex sunspots, via isolated pores,
down to the smallest yet resolved elements - so-called magnetic bright
points (MBPs). Here, we revisit the various manifestations of solar
magnetic fields by the largest European solar telescope in operation,
the 1.5-meter GREGOR telescope. We show images from the High-resolution
Fast Imager (HiFI) and spectropolarimetric data from the GREGOR Infrared
Spectrograph (GRIS). Besides, we outline resolved convective features
inside the larger structures - so-called light-bridges occurring on
large to mid-sized scales.
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Title: Science Requirement Document (SRD) for the European Solar
Telescope (EST) (2nd edition, December 2019)
Authors: Schlichenmaier, R.; Bellot Rubio, L. R.; Collados, M.;
Erdelyi, R.; Feller, A.; Fletcher, L.; Jurcak, J.; Khomenko, E.;
Leenaarts, J.; Matthews, S.; Belluzzi, L.; Carlsson, M.; Dalmasse,
K.; Danilovic, S.; Gömöry, P.; Kuckein, C.; Manso Sainz, R.;
Martinez Gonzalez, M.; Mathioudakis, M.; Ortiz, A.; Riethmüller,
T. L.; Rouppe van der Voort, L.; Simoes, P. J. A.; Trujillo Bueno,
J.; Utz, D.; Zuccarello, F.
2019arXiv191208650S Altcode:
The European Solar Telescope (EST) is a research infrastructure
for solar physics. It is planned to be an on-axis solar telescope
with an aperture of 4 m and equipped with an innovative suite of
spectro-polarimetric and imaging post-focus instrumentation. The EST
project was initiated and is driven by EAST, the European Association
for Solar Telescopes. EAST was founded in 2006 as an association
of 14 European countries. Today, as of December 2019, EAST consists
of 26 European research institutes from 18 European countries. The
Preliminary Design Phase of EST was accomplished between 2008 and
2011. During this phase, in 2010, the first version of the EST Science
Requirement Document (SRD) was published. After EST became a project
on the ESFRI roadmap 2016, the preparatory phase started. The goal
of the preparatory phase is to accomplish a final design for the
telescope and the legal governance structure of EST. A major milestone
on this path is to revisit and update the Science Requirement Document
(SRD). The EST Science Advisory Group (SAG) has been constituted by
EAST and the Board of the PRE-EST EU project in November 2017 and has
been charged with the task of providing with a final statement on the
science requirements for EST. Based on the conceptual design, the SRD
update takes into account recent technical and scientific developments,
to ensure that EST provides significant advancement beyond the current
state-of-the-art. The present update of the EST SRD has been developed
and discussed during a series of EST SAG meetings. The SRD develops
the top-level science objectives of EST into individual science
cases. Identifying critical science requirements is one of its main
goals. Those requirements will define the capabilities of EST and the
post-focus instrument suite. The technical requirements for the final
design of EST will be derived from the SRD.
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Title: Generation of solar spicules and subsequent atmospheric heating
Authors: Samanta, Tanmoy; Tian, Hui; Yurchyshyn, Vasyl; Peter, Hardi;
Cao, Wenda; Sterling, Alphonse; Erdélyi, Robertus; Ahn, Kwangsu;
Feng, Song; Utz, Dominik; Banerjee, Dipankar; Chen, Yajie
2019Sci...366..890S Altcode: 2020arXiv200602571S
Spicules are rapidly evolving fine-scale jets of magnetized plasma in
the solar chromosphere. It remains unclear how these prevalent jets
originate from the solar surface and what role they play in heating
the solar atmosphere. Using the Goode Solar Telescope at the Big Bear
Solar Observatory, we observed spicules emerging within minutes of the
appearance of opposite-polarity magnetic flux around dominant-polarity
magnetic field concentrations. Data from the Solar Dynamics Observatory
showed subsequent heating of the adjacent corona. The dynamic
interaction of magnetic fields (likely due to magnetic reconnection)
in the partially ionized lower solar atmosphere appears to generate
these spicules and heat the upper solar atmosphere.
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Title: Photospheric magnetic structure of coronal holes
Authors: Hofmeister, Stefan J.; Utz, Dominik; Heinemann, Stephan G.;
Veronig, Astrid; Temmer, Manuela
2019A&A...629A..22H Altcode: 2019arXiv190903806H
In this study, we investigate in detail the photospheric magnetic
structure of 98 coronal holes using line-of-sight magnetograms of
SDO/HMI, and for a subset of 42 coronal holes using HINODE/SOT G-band
filtergrams. We divided the magnetic field maps into magnetic elements
and quiet coronal hole regions by applying a threshold at ±25 G. We
find that the number of magnetic bright points in magnetic elements
is well correlated with the area of the magnetic elements (cc =
0.83 ± 0.01). Further, the magnetic flux of the individual magnetic
elements inside coronal holes is related to their area by a power law
with an exponent of 1.261 ± 0.004 (cc = 0.984 ± 0.001). Relating
the magnetic elements to the overall structure of coronal holes, we
find that on average (69 ± 8)% of the overall unbalanced magnetic
flux of the coronal holes arises from long-lived magnetic elements
with lifetimes > 40 h. About (22 ± 4)% of the unbalanced magnetic
flux arises from a very weak background magnetic field in the quiet
coronal hole regions with a mean magnetic field density of about
0.2-1.2 G. This background magnetic field is correlated to the flux
of the magnetic elements with lifetimes of > 40 h (cc = 0.88 ±
0.02). The remaining flux arises from magnetic elements with lifetimes
< 40 h. By relating the properties of the magnetic elements to the
overall properties of the coronal holes, we find that the unbalanced
magnetic flux of the coronal holes is completely determined by
the total area that the long-lived magnetic elements cover (cc =
0.994 ± 0.001). <P />Movie associated to Fig. 2 is available at <A
href="https://www.aanda.org/10.1051/0004-6361/201935918/olm">https://www.aanda.org</A>
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Title: Photospheric plasma and magnetic field dynamics during the
formation of solar AR 11190
Authors: Campos Rozo, J. I.; Utz, D.; Vargas Domínguez, S.; Veronig,
A.; Van Doorsselaere, T.
2019A&A...622A.168C Altcode: 2019arXiv190102437C
Context. The Sun features on its surface typical flow patterns called
the granulation, mesogranulation, and supergranulation. These patterns
arise due to convective flows transporting energy from the interior
of the Sun to its surface. The other well known elements structuring
the solar photosphere are magnetic fields arranged from single,
isolated, small-scale flux tubes to large and extended regions
visible as sunspots and active regions. <BR /> Aims: In this paper
we will shed light on the interaction between the convective flows
in large-scale cells as well as the large-scale magnetic fields in
active regions, and investigate in detail the statistical distribution
of flow velocities during the evolution and formation of National
Oceanic and Atmospheric Administration active region 11190. <BR />
Methods: To do so, we employed local correlation tracking methods
on data obtained by the Solar Dynamics Observatory in the continuum
as well as on processed line-of-sight magnetograms. <BR /> Results:
We find that the flow fields in an active region can be modelled by a
two-component distribution. One component is very stable, follows a
Rayleigh distribution, and can be assigned to the background flows,
whilst the other component is variable in strength and velocity
range and can be attributed to the flux emergence visible both in
the continuum maps as well as magnetograms. Generally, the plasma
flows, as seen by the distribution of the magnitude of the velocity,
follow a Rayleigh distribution even through the time of formation
of active regions. However, at certain moments of large-scale fast
flux emergence, a second component featuring higher velocities is
formed in the velocity magnitudes distribution. <BR /> Conclusions:
The plasma flows are generally highly correlated to the motion of
magnetic elements and vice versa except during the times of fast
magnetic flux emergence as observed by rising magnetic elements. At
these times, the magnetic fields are found to move faster than the
corresponding plasma. <P />Movie attached to Fig. 1 is available at <A
href="https://www.aanda.org/10.1051/0004-6361/201832760/olm">https://www.aanda.org</A>
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Title: The photospheric structure of coronal holes: magnetic elements
Authors: Hofmeister, Stefan; Utz, Dominik; Heinemann, Stephan; Veronig,
Astrid; Temmer, Manuela
2018csc..confE.129H Altcode:
Coronal holes attracted recently more attention by the scientific
community as they represent the source region for the fast solar wind
which is ifself an important ingredient in understanding the space
environment and space weather. Nevertheless, our knowledge about
the detailed magnetic field structure below coronal holes is quite
limited, maybe since such a research would necessarily involve the high
atmospheric and photospheric community. In this contribution we would
like to bridge this gap and investigate in detail the magnetic field
distribution below coronal holes and its relationship to the large-scale
coronal hole topology. To do so, we investigate the distribution and
properties of photospheric magnetic elements below 106 low and medium
latitude coronal holes using SDO/HMI line-of-sight magnetogram data from
2010 to 2016, and relate them to the overall properties of the coronal
holes. Since magnetic elements produce clearly visible photospheric
structures, they can be well observed and give us valuable insights into
the structure of coronal holes. We find that the distribution of the
magnetic flux of magnetic elements follows an exponential function. The
area and flux of magnetic elements are strongly related to each other
by a power law with an exponent of 1.25. The larger magnetic elements
are located at the edges of the magnetic network and seem to be the
"core" structure of coronal holes. They have lifetimes > 4 days,
i.e., longer than the timescale of the supergranulation. Further, they
contain up to 50 magnetic bright points as observed by Hinode/SOT in
the G-Band, meaning that the large magnetic elements are large clusters
of individual magnetic elements. The mean magnetic field density of
the overall coronal holes and thus their unbalanced magnetic flux
is determined by their percentage coverage with magnetic elements
at cc=0.98. Since magnetic elements are the foot points of magnetic
funnels and thus the small-scale source regions of high-speed solar
wind streams, the dependence of the coverage with magnetic elements
on the strength of coronal holes also explains the dependence of the
plasma density of high-speed streams near the Sun to the strength of
its source coronal hole. The rotation rates of the magnetic elements
match the rotation rate of the coronal hole and is surprisingly similar
to the differential rotation rate of active regions at low- and medium
latitudes, suggesting they are rooted at similar deep layers. This
also means that coronal holes do not show an abnormal rotation rate
as suggested by various authors. Finally, by projecting the magnetic
elements to AIA-171 and 193 filtergrams, we surprisingly find that the
magnetic elements are not located in the darkest regions of coronal
holes. Therefore, the vertical plasma outflow from magnetic funnels
is probably not the primary reason why coronal holes appear as dark
patches in EUV images. We conclude that magnetic elements are the
basic building blocks of coronal holes which completely determine
their magnetic properties.
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Title: Dynamcis and magnetic properties in coronal holes using
high-resolution multi-instrument solar observations
Authors: Krikova, K.; Utz, D.; Veronig, A.; Gömöry, P.; Hofmeister,
S.; Temmer, M.
2018simi.conf...31K Altcode:
Using high-resolution solar observations from the Hinode Instruments
SOT/SP, EIS and XRT as well as IRIS from a coronal hole on the 26th of
September 2017, we are investigating the dynamics within the coronal
hole visible on the specified date. Further satellite data support is
given by full disc images from SDO with the AIA and HMI instruments. EIS
and IRIS data provide us with crucial information about the plasma and
energy flow from the Sun's chromosphere into the corona using the EUV
and UV spectra and images. Investigating the magnetic configuration
as well as the dynamics and changes within the coronal hole by using
the SOT/SP data will give us additional crucial insights about the
physical processes leading to the corresponding changes in the higher
atmosphere. We compare the Hinode data with AIA and HMI data to get
a firm comprehensive picture about the connection from high resolved
photospheric fields and its dynamics within the higher layer. Within the
timeframe of the analysed EIS dataset two microflare events associated
with a solar jet were captured, originating inside the coronal hole
under investigation. We believe that it is totally worthwhile to study
these features in full detail as not so much attention was paid to high
energy processes within coronal holes and their basic relationship to
the harboring coronal hole and they show surprisingly high downflows
in the Fe XII iron line (up to 140 km/s). In the current proceeding
we will outline the state of the art of this investigation and give
an overview of the further steps necessary. The mentioned data were
obtained during a recent GREGOR campaign with the joint support of
IRIS and Hinode (HOP 338).
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Title: Does the solar granulation change with the activity cycle?
Authors: Muller, R.; Hanslmeier, A.; Utz, D.; Ichimoto, K.
2018A&A...616A..87M Altcode:
Context. Knowledge of the variation of the solar granulation properties
(contrast and scale) with the 11-yr activity cycle is useful for a
better understanding of the interaction between magnetic field and
convection at global or local scales. A varying granulation may also
contribute to irradiance variations and affect the p-mode damping
rates and lifetimes. <BR /> Aims: HINODE/SOT blue continuum images
taken in the frame of the synoptic program at the disk center on a
daily basis between November 2006 and February 2016 are used. This
period covers the minimum of activity between cycles 23 and 24 and the
maximum of cycle 24. <BR /> Methods: The sharpness of a significant
number of images was reduced because of instrumental aberrations or
inaccurate focusing. Only the sharpest images were selected for this
investigation. <BR /> Results: To be detectable with HINODE/SOT images,
the variation of the granulation contrast and of the granulation scale
at the disk center should have been larger than 3%. As it is not the
case, it is concluded that they varied by less than 3% through the
weak cycle 24.
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Title: Long-term trends of magnetic bright points: The evolution of
MBP size
Authors: Utz, D.; Van Doorsselaere, T.; Gagelmans, E.; O'Rourke, C.;
Vuerinckx, A.; Muller, R.; Veronig, A.
2018simi.conf..179U Altcode:
Magnetic Bright Points (MBPs) are small-scale, very strong,
solar magnetic field concentrations visible in the lower solar
atmosphere. While there is a large and ever-increasing knowledge base
and understanding of large-scale solar magnetic fields, i.e., sunspots
and active regions, and their involvement in the solar cycle, much
less is known about small-scale fields such as MBPs. Thus, we aim on
contributing to our understanding of these tiny, but, important solar
features by investigating the size distribution and its variation over
time. <P />For this purpose, we obtained the synoptic G-band data set
of the Hinode mission which is now since nearly 12 years in space and
operational (launched in October 2006). After careful image calibration
and selection we analysed the G-band data set with an automated MBP
identification algorithm to calculate in a next step the equivalent
diameter of the MBPs. <P />The so gained size distribution follows a
Gamma distribution with pronounced changes during the solar activity
cycle. The MBP sizes appear to be somewhat smaller during the solar
minimum and somewhat more extended during the solar maxima as expressed
by the scaleparameter of the Gamma distribution.
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Title: Modelling the solar photospheric plasma and magnetic field
dynamics during the emergence of AR 11190
Authors: Campos Rozo, Jose Ivan; Utz, Dominik; Veronig, Astrig;
Vargas Domínguez, Santiago
2018nspm.confE...1C Altcode:
The interaction between the plasma and the magnetic field has been
studied before by various authors. In this work we will show a
detailed study employing two different distributions applied to the
flow velocities during the emergence and prior evolution of AR 11190
on 11- April-2011. The velocity fields are computed from intensity as
well as LOS magnetograms by using Local Correlation Tracking (LCT)
techniques. Horizontal velocities as well as vertical velocities
show strong correlation between the emergence of new fast and strong
positive magnetic elements, and strong divergences observed from
vertical velocities calculated by LCT in continuum data. Although
there are several divergence regions within the field of view, just
the region of interest shows the emergences of new magnetic field.
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Title: Modelling the solar photospheric plasma and magnetic field
dynamics in the quiet Sun and comparison of these results with the
flow fields in an evolving active region
Authors: Campos Rozo, Jose Ivan; Utz, Dominik; Veronig, Astrid;
Vargas Domínguez, Santiago
2018simi.conf...37C Altcode:
In the present work a detailed study of the flow velocities of a quiet
solar region is made and then compared with the flow fields during the
emergence and prior to the evolution of AR-11190 on 11-April-2010. The
velocity fields are computed from intensity as well as LOS magnetograms
by using Local Correlation Tracking (LCT) techniques. The magnitudes
of the obtained velocity vectors can be modelled by a single and
simple Rayleigh distribution in the case of the quiet Sun and by a
combination of two different statistical distributions in the case of
the active region. Primarily this combination consists of a Rayleigh
distribution that models the background velocity magnitudes as well
as the general behavior of the combined velocity distribution, plus
a weaker additional component that recreates the fast changes within
the field of view. We propose two different distributions (implying
different physical interpretations) for this second component of our
combined fitting model. Generally, we can say that all the distributions
show a strong correlation between the plasma motions and the movements
of magnetic elements except during time instances when strong and fast
magnetic flux elements start to appear within the region of interest.
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Title: Long time trends of MBP characteristics
Authors: Utz, D.; Muller, R.; Van Doorsselaere, T.; Veronig, A.;
Gagelmans, E.; O'Rourke, C.; Vuerinckx, A.
2018CEAB...42...13U Altcode:
The change of Magnetic Bright Points (MBPs) characteristics over
time periods of the solar sunspot cycle is studied. MBPs are
small-scale solar magnetic field features reaching well beyond kG
magnetic field strength and visible in intergranular lines within
the solar photosphere. They are very variable and dynamic on time
scales of just a few minutes. Due to their strong magnetic field,
which resembles in shape the ideal concept of vertical flux tubes,
as well as their dynamic behaviour, they are of special interest for
wave triggering and propagation processes. On the other hand these
small-scale structures appear brighter on the solar photosphere and thus
their long time behaviour in respect of number, size, and intensity
is of great importance for the total solar irradiance variability and
thus also for climate change studies. In the current contribution we
want to have a detailed look on exactly these parameters over the
time period from end of 2006 until spring 2017 when unfortunately
the Hinode SOT/BFI and NFI CCD cameras failed and thus no more data
could be taken by the Hinode spacecrafts BFI instrument. The key
findings can be summarized as that the number at the disc centre is
variable and correlated to the sunspot cycle but shifted in regards
to it. Moreover the size distribution of MBPs varies with the cycle
indicating that fundamental magneto-convective properties might change
on the 11th-year solar-cycle time-period.
---------------------------------------------------------
Title: Small-scale dynamcis in a coronal-hole related to microflaring
events
Authors: Krikova, K.; Utz, D.; Veronig, A.; Hofmeister, S.; Temmer,
M.; Gömöry, P.; Holzknecht, L.
2018CEAB...42....8K Altcode:
Using high-resolution solar imagery and spectroscopy from the Hinode
EIS and SDO instruments, we investigate the dynamics within a coronal
hole observed on the 26th September 2017. Further data is given by
full disc images from SDO with the AIA and HMI instruments. EIS
spectra provide us with crucial information about the plasma and
energy flows from the Sun's chromosphere into the corona. Within the
timeframe of the analysed EIS dataset two microflares associated with a
jet-like event were captured, originating inside the coronal hole under
investigation. These two microflare events were analysed in the study at
hand in detail. Such recurring solar transient events could contribute
to the mass and energy input into the solar corona and also to the solar
wind. Our analysis shows that microflare temperatures can reach up to
3 MK with a hot component close to the reconnection site. Moreover an
enhanced density at the microflare region was found. The obtained EIS
ion line ratios suggest a density of up to 2.9 \cdot 10^{10} cm^{-3}.
---------------------------------------------------------
Title: Formation Heights of HINODE SOT/BFI Filters
Authors: Kuehner, O.; Utz, D.; Muller, R.; Van Doorsselaere, T.;
Magyar, N.; Veronig, A.; Campos Rozo, J. I.; Jelinek, P.
2018CEAB...42....9K Altcode:
Small-scale magnetic fields in the solar atmosphere are not static
objects with height but expand. Thus, to understand the expansion,
one can measure proxy features with various spectral filters forming in
different heights. However, this is tricky as, it is well known that the
formation height of spectral filters within the solar atmosphere depends
on the atmospheric parameters itself. This means that the spectral line
formation within small-scale magnetic fields is different compared to
the quiet Sun. To investigate the dependency of these formation heights
due to different atmospheric parameters we constructed an atmospheric
model of the Sun with an embedded flux tube fulfilling magnetostatic
conditions. We investigated the behavior of the formation heights of
the HINODE SOT/BFI spectral bands (blue, green, red continuum, G-Band,
Ca II H) in answer to varying input parameters of our atmospheric
model. The currently seen effects are not tremendous. However, this
is most likely due to the rather weak magnetic field strength achieved
so far in our magnetic flux tube models.
---------------------------------------------------------
Title: Temporal relations between magnetic bright points and the
solar sunspot cycle
Authors: Utz, Dominik; Muller, Richard; Van Doorsselaere, Tom
2017PASJ...69...98U Altcode: 2017arXiv171001678U
The Sun shows a global magnetic field cycle traditionally best visible
in the photosphere as a changing sunspot cycle featuring roughly an
11-year period. In addition we know that our host star also harbours
small-scale magnetic fields often seen as strong concentrations of
magnetic flux reaching kG field strengths. These features are situated
in inter-granular lanes, where they show up bright as so-called
magnetic bright points (MBPs). In this short paper we wish to analyse
an homogenous, nearly 10-year-long synoptic Hinode image data set
recorded from 2006 November up to 2016 February in the G-band to
inspect the relationship between the number of MBPs at the solar disc
centre and the relative sunspot number. Our findings suggest that the
number of MBPs at the solar disc centre is indeed correlated to the
relative sunspot number, but with the particular feature of showing
two different temporal shifts between the decreasing phase of cycle 23
including the minimum and the increasing phase of cycle 24 including
the maximum. While the former is shifted by about 22 months, the latter
is only shifted by less than 12 months. Moreover, we introduce and
discuss an analytical model to predict the number of MBPs at the solar
disc centre purely depending on the evolution of the relative sunspot
number as well as the temporal change of the relative sunspot number and
two background parameters describing a possibly acting surface dynamo
as well as the strength of the magnetic field diffusion. Finally,
we are able to confirm the plausibility of the temporal shifts by a
simplistic random walk model. The main conclusion to be drawn from
this work is that the injection of magnetic flux, coming from active
regions as represented by sunspots, happens on faster time scales than
the removal of small-scale magnetic flux elements later on.
---------------------------------------------------------
Title: P-mode induced convective collapse in vertical expanding
magnetic flux tubes?
Authors: Utz, D.; van Doorsselaere, T.; Magyar, N.; Bárta, M.;
Campos Rozo, J. I.
2017IAUS..327...86U Altcode:
Small-scale kG strong magnetic field elements in the solar photosphere
are often identified as so-called magnetic bright points (MBPs). In
principle these MBPs represent the cross-section of a vertical,
strong, magnetic flux tube which is expanding with height in the
solar atmosphere. As these magnetic elements represent possible MHD
wave guides, a significant interest has been already paid to them
from the viewpoint of observations and simulations. In this work we
would like to shed more light on a possible scenario for the creation
of such strong magnetic field concentrations. The accepted standard
scenario involves the convective collapse process. In this ongoing
work we will show indications that this convective collapse process may
become triggered by sufficiently strong pressure disturbances. However,
it is highly unlikely that p-mode waves can be of such a strength.
---------------------------------------------------------
Title: Latitude dependence of the solar granulation during the
minimum of activity in 2009
Authors: Muller, R.; Hanslmeier, A.; Utz, D.
2017A&A...598A...6M Altcode:
Context. Knowledge of the latitude variation of the solar granulation
properties (contrast and scale) is useful to better understand
interactions between magnetic field, convection, differential rotation,
and meridional circulation in the solar atmosphere. <BR /> Aims: We
investigated the latitude dependence of the contrast and scale of the
solar granulation, with the help of HINODE/SOT blue continuum images
taken in the frame of the HOP 79 program, along the central meridian
and along the equator on a monthly basis in 2009 during the last solar
minimum of activity. <BR /> Methods: We selected the sharpest images
in latitude and longitude intervals. The selected images in all the N-S
and E-W scans taken in 2009 were combined to get statistically reliable
results. <BR /> Results: The contrast of the solar granulation decreases
towards the poles and the scale increases, but not regularly since a
perturbation occurs at around 60° where both quantities return close
to their values at the disk center. <BR /> Conclusions: Such a latitude
variation in a period of minimum of activity (2009), is probably not
due to magnetic field, neither the quiet magnetic field at the surface,
nor the strong magnetic flux tubes associated with active regions,
which could be embedded more or less deeply in the convection zone
before they reach the surface. The decrease in contrast and increase in
scale towards the pole seem to be related to the differential rotation
and the perturbation around 60° to the meridional circulation.
---------------------------------------------------------
Title: The Effect of Area Averaging on the Approximated Profile of
the H α Spectral Line
Authors: Bodnárová, M.; Utz, D.; Rybák, J.
2016ASPC..504...23B Altcode:
The Hα line is massively used as a diagnostics of the
chromosphere. Often one needs to average the line profile over some
area to increase the signal to noise ratio. Thus it is important to
understand how derived parameters vary with changing approximations. In
this study we investigate the effect of spatial averaging of a selected
area on the temporal variations of the width, the intensity and the
Dopplershift of the Hα spectral line profile. The approximated profile
was deduced from co-temporal observations in five points throughout
the Hα line profile obtained by the tunable Lyot filter installed
on the Dutch Open Telescope. We found variations of the intensity and
the Doppler velocities, which were independent of the size of the area
used for the computation of the area averaged Hα spectral line profile.
---------------------------------------------------------
Title: Long-term trends of magnetic bright points. I. Number of
magnetic bright points at disc centre
Authors: Utz, D.; Muller, R.; Thonhofer, S.; Veronig, A.; Hanslmeier,
A.; Bodnárová, M.; Bárta, M.; del Toro Iniesta, J. C.
2016A&A...585A..39U Altcode: 2015arXiv151107767U
Context. The Sun shows an activity cycle that is caused by its varying
global magnetic field. During a solar cycle, sunspots, I.e. extended
regions of strong magnetic fields, occur in activity belts that are
slowly migrating from middle to lower latitudes, finally arriving
close to the equator during the cycle maximum phase. While this
and other facts about the strong extended magnetic fields have been
well known for centuries, much less is known about the solar cycle
evolution of small-scale magnetic fields. Thus the question arises
if similar principles exist for small-scale magnetic fields. <BR />
Aims: To address this question, we study magnetic bright points (MBPs)
as proxies for such small-scale, kG solar magnetic fields. This study is
based on a homogeneous data set that covers a period of eight years. The
number of detected MBPs versus time is analysed to find out if there
is an activity cycle for these magnetic features too and, if so, how
it is related to the sunspot cycle. <BR /> Methods: An automated MBP
identification algorithm was applied to the synoptic Hinode/SOT G-band
data over the period November 2006 to August 2014, I.e. covering the
decreasing phase of Cycle 23 and the rise, maximum, and early decrease
of Cycle 24. This data set includes, at the moment of investigation, a
total of 4162 images, with about 2.9 million single MBP detections. <BR
/> Results: After a careful preselection and monthly median filtering
of the data, the investigation revealed that the number of MBPs close
to the equator is coupled to the global solar cycle but shifted in time
by about 2.5 yr. Furthermore, the instantaneous number of detected MBPs
depends on the hemisphere, with one hemisphere being more prominent,
I.e. showing a higher number of MBPs. After the end of Cycle 23 and at
the starting point of Cycle 24, the more active hemisphere changed from
south to north. Clear peaks in the detected number of MBPs are found
at latitudes of about ±7°, in congruence with the positions of the
sunspot belts at the end of the solar cycle. <BR /> Conclusions: These
findings suggest that there is indeed a coupling between the activity of
MBPs close to the equator with the global magnetic field. The results
also indicate that a significant fraction of the magnetic flux that
is visible as MBPs close to the equator originates from the sunspot
activity belts. However, even during the minimum of MBP activity,
a percentage as large as 60% of the maximum number of detected MBPs
has been observed, which may be related to solar surface dynamo action.
---------------------------------------------------------
Title: Fulfilling Magnetostatic Conditions in Numerical Simulations
of Expanding Flux Tubes
Authors: Utz, D.; Van Doorsselaere, T.; Kühner, O.; Magyar, N.;
Calvo Santamaria, I.; Campos Rozo, J. I.
2016CEAB...40....9U Altcode:
A long-lasting problem of solar physics is the topic of the heating
of the outer atmospheric layers of the Sun. Among the possible
heating scenarios are wave driven heating processes. In this scenario
disturbances and turbulence in the photosphere of the Sun causes the
creation of waves which propagate upwards into the higher atmosphere
where these waves are at least partially damped and absorbed, causing
heating of the atmosphere. Nowadays it is thought that especially
MHD waves play an important role in such heating scenarios. The
created MHD waves are guided especially well along strong vertical
magnetic field configurations, so-called flux-tubes, into the higher
atmosphere. To obtain deeper insights into this fascinating topic,
numerical simulations are a useful tool at hand. However, up to now
it is still quite common to assume simple non stratified flux tubes
which feature in addition weak magnetic field strengths. While this
makes the modeling of the solar atmosphere and the magnetic field
configuration much easier, the results might be changed drastically by
these simplifications. In the current contribution we wish to outline
a method of how to construct self-consistent, magneto-static flux
tube atmospheres.
---------------------------------------------------------
Title: Parallelization of the SIR code for the investigation of
small-scale features in the solar photosphere
Authors: Thonhofer, Stefan; Bellot Rubio, Luis R.; Utz, Dominik;
Hanslmeier, Arnold; Jurçák, Jan
2015IAUS..305..251T Altcode: 2015arXiv150303710T
Magnetic fields are one of the most important drivers of the highly
dynamic processes that occur in the lower solar atmosphere. They span a
broad range of sizes, from large- and intermediate-scale structures such
as sunspots, pores and magnetic knots, down to the smallest magnetic
elements observable with current telescopes. On small scales, magnetic
flux tubes are often visible as Magnetic Bright Points (MBPs). Apart
from simple V/I magnetograms, the most common method to deduce their
magnetic properties is the inversion of spectropolarimetric data. Here
we employ the SIR code for that purpose. SIR is a well-established
tool that can derive not only the magnetic field vector and other
atmospheric parameters (e.g., temperature, line-of-sight velocity),
but also their stratifications with height, effectively producing
3-dimensional models of the lower solar atmosphere. In order to enhance
the runtime performance and the usability of SIR we parallelized the
existing code and standardized the input and output formats. This and
other improvements make it feasible to invert extensive high-resolution
data sets within a reasonable amount of computing time. An evaluation
of the speedup of the parallel SIR code shows a substantial improvement
in runtime.
---------------------------------------------------------
Title: Magnetic bright point dynamics and evolutions observed by
Sunrise/IMaX and other instruments
Authors: Utz, D.; del Toro Iniesta, J. C.; Bellot Rubio, L.; Thonhofer,
S.; Jurčák, J.
2015hsa8.conf..689U Altcode:
In this proceeding we will have a closer look on recent observations
and results regarding the dynamics and evolution of so-called magnetic
bright points (MBPs). MBPs are manifestations of kG magnetic field
strong flux concentrations seen in the solar photosphere. They belong
to the class of small-scale solar magnetic features with diameters
starting from low values around the current observational resolution
limit - about 100 km - up to a few hundred km. They might play an
important role in several key research questions like the total solar
irradiance variation (TSI variation) as well as the solar atmospheric
heating problem. Especially their dynamic behaviour is of interest
for the heating problem as they might trigger all kinds of MHD waves
which travel up to the higher solar atmospheric layers, where they can
get damped leading to a heating of the plasma. Furthermore they might
engage in magnetic field reconnection processes leading consequently
also to a heating. Due to these reasons, and also for the sake of a
better understanding of the physical processes involved on small-scales,
detailed investigations on the dynamical behaviour and evolution of
such magnetic field proxies like MBPs is in order. In this conference
proceeding we wish to give in a first part an overview about the
obtained knowledge so far. In a second part we highlight recent results
regarding the dynamical evolution of plasma parameters of MBPs such as
magnetic field strength, temperature, and line of sight velocity. This
proceeding is completed by an outlook on what can and should be done
in the near future with available data from recent telescopes.
---------------------------------------------------------
Title: Long time variations of Magnetic Bright Points observed
by Hinode/SOT
Authors: Utz, D.; del Toro Iniesta, J. C.; Bellot-Rubio, L.;
Bodnárová, M.; Muller, R.; Bárta, M.; Thonhofer, S.; Hanslmeier, A.
2015CEAB...39...91U Altcode:
Magnetic bright points (MBPs) are manifestations of small-scale solar
magnetic flux concentrations, best observable due to their high contrast
in molecular bands like the G-band. Moreover, they are among the most
interesting magnetic features to be studied in high spatial and temporal
resolution in the solar photosphere. Their relevance for solar physics
is not only given by their contribution to fundamental solar plasma
physics on small scales but in addition due to their involvement in
processes like the solar atmospheric heating problem (chromosphere
and corona), their influence on granulation and hence the convective
energy transport, as well as their contribution to the variations in
total solar irradiance caused by their higher relative intensity. In
this ongoing study we focus on the long-time evolution of statistical
parameters of MBPs over the solar cycle. Are parameters like the mean
intensity, average size/diameter, and number of MBPs per unit surface
element variable with time? If so, how do these parameters vary and is
there a relationship to the solar cycle? In the actual contribution
we will discuss preliminary results regarding the variation of the
number of MBPs with time. We saw a decrease in the number of MBPs for
the first years of observation (2006 until 2011) with two distinct
local minima in the years 2009 and 2011. After 2011 the number of MBPs
is increasing again along with an increase in general solar activity
(as seen by the number of sunspots, flares, and CMEs).
---------------------------------------------------------
Title: The Formation and Disintegration of Magnetic Bright Points
Observed by Sunrise/IMaX
Authors: Utz, D.; del Toro Iniesta, J. C.; Bellot Rubio, L. R.;
Jurčák, J.; Martínez Pillet, V.; Solanki, S. K.; Schmidt, W.
2014ApJ...796...79U Altcode: 2014arXiv1411.3240U
The evolution of the physical parameters of magnetic bright points
(MBPs) located in the quiet Sun (mainly in the interwork) during
their lifetime is studied. First, we concentrate on the detailed
description of the magnetic field evolution of three MBPs. This
reveals that individual features follow different, generally complex,
and rather dynamic scenarios of evolution. Next, we apply statistical
methods on roughly 200 observed MBP evolutionary tracks. MBPs are found
to be formed by the strengthening of an equipartition field patch,
which initially exhibits a moderate downflow. During the evolution,
strong downdrafts with an average velocity of 2.4 km s<SUP>-1</SUP>
set in. These flows, taken together with the concurrent strengthening of
the field, suggest that we are witnessing the occurrence of convective
collapses in these features, although only 30% of them reach kG field
strengths. This fraction might turn out to be larger when the new 4
m class solar telescopes are operational as observations of MBPs with
current state of the art instrumentation could still be suffering from
resolution limitations. Finally, when the bright point disappears
(although the magnetic field often continues to exist) the magnetic
field strength has dropped to the equipartition level and is generally
somewhat weaker than at the beginning of the MBP's evolution. Also,
only relatively weak downflows are found on average at this stage of
the evolution. Only 16% of the features display upflows at the time
that the field weakens, or the MBP disappears. This speaks either for
a very fast evolving dynamic process at the end of the lifetime, which
could not be temporally resolved, or against strong upflows as the cause
of the weakening of the field of these magnetic elements, as has been
proposed based on simulation results. It is noteworthy that in about 10%
of the cases, we observe in the vicinity of the downflows small-scale
strong (exceeding 2 km s<SUP>-1</SUP>) intergranular upflows related
spatially and temporally to these downflows. The paper is complemented
by a detailed discussion of aspects regarding the applied methods,
the complementary literature, and in depth analysis of parameters
like magnetic field strength and velocity distributions. An important
difference to magnetic elements and associated bright structures in
active region plage is that most of the quiet Sun bright points display
significant downflows over a large fraction of their lifetime (i.e.,
in more than 46% of time instances/measurements they show downflows
exceeding 1 km s<SUP>-1</SUP>).
---------------------------------------------------------
Title: On Dynamics of G-Band Bright Points
Authors: Bodnárová, M.; Utz, D.; Rybák, J.
2014SoPh..289.1543B Altcode: 2013arXiv1312.5464B
Various parameters describing the dynamics of G-band bright points
(GBPs) were derived from G-band images, acquired by the Dutch Open
Telescope (DOT), of a quiet region close to the disk center. Our
study is based on four commonly used diagnostics (effective velocity,
change in the effective velocity, change in the direction angle, and
centrifugal acceleration) and two new ones (rate of motion and time lag
between recurrence of GBPs). The results concerning the commonly used
parameters are in agreement with previous studies for a comparable
spatial and temporal resolution of the used data. The most probable
value of the effective velocity is ∼ 0.9 km s<SUP>−1</SUP>,
whereas we found a deviation of the effective velocity distribution
from the expected Rayleigh function for velocities in the range from
2 to 4 km s<SUP>−1</SUP>. The change in the effective velocity
distribution is consistent with a Gaussian one with FWHM=0.079 km
s<SUP>−2</SUP>. The distribution of the centrifugal acceleration
exhibits a highly exponential nature (a symmetric Gaussian centered
at the zero value). To broaden our understanding of the dynamics of
GBPs, two new parameters were defined: the real displacement between
their appearance and disappearance (rate of motion) and the frequency
of their recurrence at the same locations (time lag). For ∼ 45 % of
the tracked GBPs, their displacement was found to be small compared to
their size (the rate of motion smaller than one). The locations of the
tracked GBPs mainly cover the boundaries of supergranules representing
the network, and there is no significant difference in the locations
of GBPs with small (m<1) and large (m>2) values of the rate of
motion. We observed a difference in the overall trend of the obtained
distribution for the values of the time lag smaller (slope of the trend
line being −0.14) and greater (−0.03) than ∼ 7 min. The time
lags mostly lie within the interval of ∼ 2 - 3 min, with those up to
∼ 4 min being more abundant than longer ones. Results for both new
parameters indicate that the locations of different dynamical types
of GBPs (stable/farther traveling or with short/long lifetimes) are
bound to the locations of more stable and long-living magnetic field
concentrations. Thus, the disappearance/reappearance of the tracked
GBPs cannot be perceived as the disappearance/reappearance of their
corresponding magnetic field concentrations.
---------------------------------------------------------
Title: Two-dimensional segmentation of small convective patterns in
radiation hydrodynamics simulations
Authors: Lemmerer, B.; Utz, D.; Hanslmeier, A.; Veronig, A.; Thonhofer,
S.; Grimm-Strele, H.; Kariyappa, R.
2014A&A...563A.107L Altcode: 2015arXiv150500325L
Context. Recent results from high-resolution solar granulation
observations indicate the existence of a population of small granular
cells that are smaller than 600 km in diameter. These small convective
cells strongly contribute to the total area of granules and are located
in the intergranular lanes, where they form clusters and chains. <BR />
Aims: We study high-resolution radiation hydrodynamics simulations of
the upper convection zone and photosphere to detect small granular
cells, define their spatial alignment, and analyze their physical
properties. <BR /> Methods: We developed an automated image-segmentation
algorithm specifically adapted to high-resolution simulations to
identify granules. The resulting segmentation masks were applied to
physical quantities, such as intensity and vertical velocity profiles,
provided by the simulation. A new clustering algorithm was developed
to study the alignment of small granular cells. <BR /> Results:
Small granules make a distinct contribution to the total area of
granules and form clusters of chain-like alignments. The simulation
profiles demonstrate a different nature for small granular cells
because they exhibit on average lower intensities, lower horizontal
velocities, and are located deeper inside of convective layers than
regular granules. Their intensity distribution deviates from a normal
distribution as known for larger granules, and follows a Weibull
distribution.
---------------------------------------------------------
Title: Fractal Dimension Analysis of Solar Granulation- Boxcounting
dimension
Authors: Hanslmeier, A.; Lemmerer, B.; Utz, D.; Muller, R.; Muthsam, H.
2014CEAB...38...11H Altcode:
The fractal dimension of high resolution Hinode solar granulation
observations and numerical simulations is studied and the results are
compared. These observations are not influenced by atmospheric seeing
conditions and therefore allow a more realistic estimate of the fractal
dimension than in previous works. Though arriving at similar results for
observations and simulation data, non integer fractal dimension <2,
some differences in the numerical values occur, and these are discussed.
---------------------------------------------------------
Title: Detection of small convective patterns in observations and
simulations
Authors: Lemmerer, B.; Utz, D.; Hanslmeier, A.; Veronig, A.;
Grimm-Strele, H.; Thonhofer, S.; Piantschitsch, I.
2014CEAB...38...19L Altcode:
Recent results from high resolution solar granulation observations
indicate the existence of a population of small granular cells on
scales below 600 km in diameter, located in the intergranular lanes. We
studied a set of Hinode SOT images and high resolution radiation
hydrodynamics simulations in order to analyze small granular cells and
to study their physical properties. An automated image segmentation
algorithm specifically adapted to high resolution simulations for the
identification of granules was developed. The algorithm was also used
to analyze and compare physical quantities provided by the simulation
and the observations. We found that small granules make a distinct
contribution to the total area of granules. Both in observations and
simulations, small granular cells exhibit on average lower intensities
and vertical velocities.
---------------------------------------------------------
Title: Solar Ca II K plage regions as proxies for magnetic fields
of solar like stars
Authors: Guttenbrunner, S.; Hanslmeier, A.; Utz, D.; Lemmerer, B.;
Piantschitsch, I.; Thonhofer, S.
2014CEAB...38...81G Altcode:
Solar plage regions can be observed directly, whereas plage regions as
well as star-spots on solar like stars, can only be detected via their
contribution to spectral irradiances of these stars. Such a spectral
irradiance can be modelled by fractions belonging to the quiet star,
the plage regions, and the star-spots. The idea is, to measure these
fractions as well as the intensity enhancement due to plage regions
on our Sun and then use this information to be able to model solar
like stars. We verify the close connection between the size of the
plage regions and the luminosity of the Sun, given by a correlation
coefficient of 0.822. The size of the plage regions varies from 0%,
when the Sun is very quiet, up to 2.7% for a more active Sun (a complete
solar cycle is not yet analysed and hence our study does not contain an
activity maximum). The used data sets are full-disc images taken by the
RISE/PSPT instrument during the period from 2005 to 2012, at the MLSO.
---------------------------------------------------------
Title: Two-Fluid 2.5D MHD-Code for Simulations in the Solar Atmosphere
Authors: Piantschitsch, I.; Amerstorfer, U.; Thalmann, J.; Utz, D.;
Hanslmeier, A.; Bárta, M.; Thonhofer, S.; Lemmerer, B.
2014CEAB...38...59P Altcode:
We investigate magnetic reconnection due to the evolution of magnetic
flux tubes in the solar chromosphere. We developed a new numerical
two-fluid magnetohydrodynamic (MHD) code which will perform a 2.5D
simulation of the dynamics from the upper convection zone up to the
transition region. Our code is based on the Total Variation Diminishing
Lax-Friedrichs scheme and makes use of an alternating-direction implicit
method, in order to accommodate the two spatial dimensions. Since we
apply a two-fluid model for our simulations, the effects of ion-neutral
collisions, ionization/recombination, thermal/resistive diffusivity
and collisional/resistive heating are included in the code. As initial
conditions for the code we use analytically constructed vertically open
magnetic flux tubes within a realistic stratified atmosphere. Initial
MHD tests have already shown good agreement with known results of
numerical MHD test problems like e.g. the Orszag-Tang vortex test.
---------------------------------------------------------
Title: New insights into the evolution of magnetic bright point
plasma parameters
Authors: Utz, Dominik; Hanslmeier, Arnold; Bellot Rubio, L. R.;
Del Toro Iniesta, Jose Carlos; Jurcak, Jan
2014cosp...40E3448U Altcode:
The dynamics within the solar atmosphere are governed by the Suńs
magnetic fields. In the recent years the resolution limits were steadily
driven up by better and better instruments and telescopes (like Hinode,
Sunrise, NST, Gregor, ..) leading to higher resolved data. Therefore
the interest in ever smaller magnetic field structures within the solar
atmosphere rises. Among the smallest yet identified structures are
so-called magnetic bright points (MBPs). These features are thought to
be made up of single flux tubes and they have been studied exhaustively
in the Fraunhofer G-band since the 70´s of the last century. They are
important features not only due to their small scale (about 200 km in
diameter) and hence used as proxies for the smallest solar magnetic
field physics and processes, but also because they are involved in
topics like the chromospheric/coronal heating problem or the total
solar irradiance variation. In the current contribution we want to
study the evolution of important plasma parameters of MBPs, such
as temperature, magnetic field strength and line of sight velocity,
to get a deeper understanding of the involved physics and occuring
processes. Among the used data will be G-band filtergam data from
Hinode/SOT and spectro-polarimetric data from the IMaX instrument
onboard the Sunrise mission.
---------------------------------------------------------
Title: New insights into the temporal evolution of MBPs
Authors: Utz, D.; del Toro Iniesta, J. C.; Bellot Rubio, L. R.;
Jurčak, J.; Thonhofer, S.; Bodnárová, M.; Hanslmeier, A.; Lemmerer,
B.; Piantschitsch, I.; Guttenbrunner, S.
2014CEAB...38...73U Altcode:
Magnetic bright points (MBPs) are among the most fascinating and
interesting manifestations of small-scale solar magnetic fields. In the
present work the temporal evolution of MBPs is followed in data sets
taken by the Hinode satellite. The analysed data and obtained results
confirm a recently presented study done with Sunrise/IMaX data, namely
that MBPs are features undergoing fast evolution with magnetic fields
starting around the equipartition field strength, then showing strong
downflows (between 2 to 4 km/s) causing the magnetic field to amplify
into the kG range (700 to 1500 G) before dissolving again. Furthermore
the initial field inclinations depend on the initial magnetic field
strengths and show an evolution with more vertical angles at some
point during the evolution.
---------------------------------------------------------
Title: Parallelization of the SIR code
Authors: Thonhofer, S.; Bellot Rubio, L. R.; Utz, D.; Jurčak, J.;
Hanslmeier, A.; Piantschitsch, I.; Pauritsch, J.; Lemmerer, B.;
Guttenbrunner, S.
2014CEAB...38...31T Altcode:
A high-resolution 3-dimensional model of the photospheric magnetic
field is essential for the investigation of small-scale solar magnetic
phenomena. The SIR code is an advanced Stokes-inversion code that
deduces physical quantities, e.g. magnetic field vector, temperature,
and LOS velocity, from spectropolarimetric data. We extended this code
by the capability of directly using large data sets and inverting the
pixels in parallel. Due to this parallelization it is now feasible to
apply the code directly on extensive data sets. Besides, we included
the possibility to use different initial model atmospheres for the
inversion, which enhances the quality of the results.
---------------------------------------------------------
Title: Temporal variations in solar magnetic bright points intensity
and plasma parameters
Authors: Jurčák, J.; Utz, D.; Bellot Rubio, L. R.
2013JPhCS.440a2032J Altcode:
Magnetic bright points are one of the finest magnetic structures
observed in the solar atmosphere. They possibly represent single
flux tubes in quiet Sun regions. Their formation is described by the
convective collapse model, while the decay phase of these structures
is not well characterized yet. We attempt to follow the evolution of a
few selected examples of MBPs and to study their changes in brightness
and also the variations of plasma parameters during their lifetime. We
use data from the Hinode satellite and the Sunrise mission. The G-band
observations taken with a cadence of 30 seconds by the Hinode Solar
Optical Telescope (SOT) show very fast changes of the maximum intensity
of these structures. The complementary spectropolarimetric data, which
are used to estimate the plasma parameters, were taken with a cadence
of approximately two minutes. The variations of plasma parameters
cannot be matched one to one to the changes in intensity due to the
different temporal resolution. However, the slow changes of intensity
with large amplitude are matched with variations of magnetic field
strength and line-of-sight (LOS) velocity. The Sunrise/IMaX data have
a temporal resolution of 32 seconds and show fast variations in the
line wing intensity. These variations are associated with changes in
the magnetic field strength and LOS velocity.
---------------------------------------------------------
Title: Variations of Magnetic Bright Point Properties with Longitude
and Latitude as Observed by Hinode/SOT G-band Data
Authors: Utz, D.; Hanslmeier, A.; Veronig, A.; Kühner, O.; Muller,
R.; Jurčák, J.; Lemmerer, B.
2013SoPh..284..363U Altcode: 2012arXiv1212.1310U
Small-scale magnetic fields can be observed on the Sun in
high-resolution G-band filtergrams as magnetic bright points (MBPs). We
study Hinode/Solar Optical Telescope (SOT) longitude and latitude scans
of the quiet solar surface taken in the G-band in order to characterise
the centre-to-limb dependence of MBP properties (size and intensity). We
find that the MBP's sizes increase and their intensities decrease
from the solar centre towards the limb. The size distribution can be
fitted using a log-normal function. The natural logarithm of the mean
(μ parameter) of this function follows a second-order polynomial
and the generalised standard deviation (σ parameter) follows a
fourth-order polynomial or equally well (within statistical errors)
a sine function. The brightness decrease of the features is smaller
than one would expect from the normal solar centre-to-limb variation;
that is to say, the ratio of a MBP's brightness to the mean intensity
of the image increases towards the limb. The centre-to-limb variations
of the intensities of the MBPs and the quiet-Sun field can be fitted by
a second-order polynomial. The detailed physical process that results
in an increase of a MBP's brightness and size from Sun centre to the
limb is not yet understood and has to be studied in more detail in
the future.
---------------------------------------------------------
Title: Magnetic field strength distribution of magnetic bright points
inferred from filtergrams and spectro-polarimetric data
Authors: Utz, D.; Jurčák, J.; Hanslmeier, A.; Muller, R.; Veronig,
A.; Kühner, O.
2013A&A...554A..65U Altcode: 2013arXiv1304.5508U
Context. Small scale magnetic fields can be observed on the Sun in
G-band filtergrams as magnetic bright points (MBPs) or identified in
spectro-polarimetric measurements due to enhanced signals of Stokes
profiles. These magnetic fields and their dynamics play a crucial role
in understanding the coronal heating problem and also in surface dynamo
models. MBPs can theoretically be described to evolve out of a patch of
a solar photospheric magnetic field with values below the equipartition
field strength by the so-called convective collapse model. After the
collapse, the magnetic field of MBPs reaches a higher stable magnetic
field level. <BR /> Aims: The magnetic field strength distribution of
small scale magnetic fields as seen by MBPs is inferred. Furthermore,
we want to test the model of convective collapse and the theoretically
predicted stable value of about 1300 G. <BR /> Methods: We used four
different data sets of high-resolution Hinode/SOT observations that were
recorded simultaneously with the broadband filter device (G-band, Ca
II-H) and the spectro-polarimeter. To derive the magnetic field strength
distribution of these small scale features, the spectropolarimeter
(SP) data sets were treated by the Merlin inversion code. The four data
sets comprise different solar surface types: active regions (a sunspot
group and a region with pores), as well as quiet Sun. <BR /> Results:
In all four cases the obtained magnetic field strength distribution of
MBPs is similar and shows peaks around 1300 G. This agrees well with the
theoretical prediction of the convective collapse model. The resulting
magnetic field strength distribution can be fitted in each case by a
model consisting of log-normal components. The important parameters,
such as geometrical mean value and multiplicative standard deviation,
are similar in all data sets, so only the relative weighting of the
components is different.
---------------------------------------------------------
Title: The Height Evolution of the "True" Coronal Mass Ejection Mass
derived from STEREO COR1 and COR2 Observations
Authors: Bein, B. M.; Temmer, M.; Vourlidas, A.; Veronig, A. M.;
Utz, D.
2013ApJ...768...31B Altcode: 2013arXiv1303.3372B
Using combined STEREO-A and STEREO-B EUVI, COR1, and COR2 data, we
derive deprojected coronal mass ejection (CME) kinematics and CME "true"
mass evolutions for a sample of 25 events that occurred during 2007
December to 2011 April. We develop a fitting function to describe the
CME mass evolution with height. The function considers both the effect
of the coronagraph occulter, at the beginning of the CME evolution,
and an actual mass increase. The latter becomes important at about
10-15 R <SUB>⊙</SUB> and is assumed to mostly contribute up to
20 R <SUB>⊙</SUB>. The mass increase ranges from 2% to 6% per R
<SUB>⊙</SUB> and is positively correlated to the total CME mass. Due
to the combination of COR1 and COR2 mass measurements, we are able to
estimate the "true" mass value for very low coronal heights (<3 R
<SUB>⊙</SUB>). Based on the deprojected CME kinematics and initial
ejected masses, we derive the kinetic energies and propelling forces
acting on the CME in the low corona (<3 R <SUB>⊙</SUB>). The
derived CME kinetic energies range between 1.0-66 × 10<SUP>23</SUP>
J, and the forces range between 2.2-510 × 10<SUP>14</SUP> N.
---------------------------------------------------------
Title: Creating 3-dimensional Models of the Photosphere using the
SIR Code
Authors: Thonhofer, S.; Utz, D.; Jurčák, J.; Pauritsch, J.;
Hanslmeier, A.; Lemmerer, B.
2013CEAB...37..471T Altcode:
A high-resolution 3-dimensional model of the photospheric magnetic
field is essential for the investigation of magnetic features such
as sunspots, pores or smaller elements like single flux tubes seen
as magnetic bright points. The SIR code is an advanced inversion code
that retrieves physical quantities, e.g. magnetic field, from Stokes
profiles. Based on this code, we developed a program for automated
inversion of Hinode SOT/SP data and for storing these results in
3-dimensional data cubes in the form of fits files. We obtained models
of the temperature, magnetic field strength, magnetic field angles
and LOS-velocity in a region of the quiet sun. We will give a first
discussion of those parameters in regards of small scale magnetic
fields and what we can obtain and learn in the future.
---------------------------------------------------------
Title: A Magnetic Bright Point Case Study
Authors: Utz, D.; Jurčák, J.; Bellot-Rubio, L.; del Toro Iniesta,
J. C.; Thonhofer, S.; Hanslmeier, A.; Veronig, A.; Muller, R.;
Lemmerer, B.
2013CEAB...37..459U Altcode:
Due to its magnetic fields our host star - the Sun - becomes the
interesting object for research as we know it. The magnetic fields
themselves cover different spatial, lifetime and strength scales and
reach down from enormous flux concentrations like active sunspot
groups to single isolated magnetic flux tubes and even weaker,
predominantly inclined intranetwork structures. Flux tubes can be seen
in filtergram observations as magnetic bright points (MBPs). They are
of interest for research not only due to their sheer existence but
due to their important role in atmospheric heating (wave heating as
well as reconnection processes), to their role in the understanding
of creation and annihilation of magnetic fields as well as to their
influence on the total solar irradiance variation. In this study we
present a close look onto an evolutionary track of an MBP from its
formation to its disintegration. Physical quantities of MBPs like
their magnetic field strength and inclination, their line-of-sight
velocity, and their temperature at different heights are inferred
from the inversion of spectropolarimetric data. Original data are
taken from the Sunrise/IMaX instrument and constitute a time series
of some 60 min. The presented case resembles the convective collapse
model and is in agreement with previous studies.
---------------------------------------------------------
Title: 3D Image Segmentation Applied to Solar RHD Simulations
Authors: Lemmerer, B.; Utz, D.; Hanslmeier, A.; Veronig, A.;
Grimm-Strele, H.; Thonhofer, S.; Muthsam, H.
2013CEAB...37..477L Altcode:
3D simulation models based on Magneto-hydrodynamics (MHD) and
Radiation-hydrodynamics (RHD) equations give insight into the evolution
of magnetic fields and convective motions in the solar atmosphere. The
analysis of huge amount of data require the development of automated
segmentation algorithms. A newly developed 3D segmentation algorithm
will be introduced in order to extract and trace convective downflows
and is applied to the numerical simulation code ANTARES. The algorithm
segments strong downflow velocities resulting in tube-like structures
which enables us to analyze the motions with respect to variations
of physical parameters over height as well as their evolution with
time. Analysis of the segmented structures shows that narrower parts
tend to have higher velocities. High temporal variations in the lower
model photosphere indicate less stable structures over time in this
layer. The mean temperature within the downflow is cooler than in the
horizontally averaged simulation box. The analysis of the behavior of
vortex flows demonstrates a constant high vorticity within the segment
and a linear dependency to the vertical velocity. It appears that
vortex flows are strongly present within dominant convective downflows.
---------------------------------------------------------
Title: The Solar Convection over a Solar Cycle
Authors: Hanslmeier, A.; Muller, R.; Utz, D.
2012ASPC..463..115H Altcode:
We study the variation of granular size and contrast over a solar
activity cycle. Two different homogeneous data samples were used, from
Pic du Midi and from Hinode. The results do not confirm previous values
cited in the literature. From the Hinode data the granulation seems to
be constant, the trend found may be of instrumental degradation. We
try to explain the result by other observations like the total solar
irradiance variation. This variation was small over the past five
years and may explain why in the case of Hinode data no significant
variations were found.
---------------------------------------------------------
Title: Dependence of Velocity Distributions of Small-Scale Magnetic
Fields Derived from Hinode/SOT G-band Filtergrams on the Temporal
Resolution of the Used Data Sets
Authors: Utz, D.; Hanslmeier, A.; Muller, R.; Veronig, A.; Rybák,
J.; Muthsam, H.
2012ASPC..454...55U Altcode:
The dynamics of isolated small-scale fields in terms of velocities of
magnetic bright points (MBPs) is addressed in this contribution. The
empirically determined linear relation between the observed width
parameter for the Rayleigh velocity distribution of MBPs versus the
temporal cadence of the acquired data is studied by simulations and a
simple analytical model. The results of the model and the simulation
agree with the found relation for the observations. The conclusion we
draw from the model is that there may be no characteristic velocity
for MBPs at all.
---------------------------------------------------------
Title: Automated image inversion using SIR compared to MERLIN Code
Authors: Thonhofer, S.; Utz, D.; Pauritsch, J.; Hanslmeier, A.;
Jurčak, J.; Lemmerer, B.; Kühner, O.
2012CEAB...36...35T Altcode:
The SIR code retrieves magnetic and thermodynamic parameters of the
solar atmosphere from the Stokes profiles. By means of this tool,
the stratification of physical quantities from spectropolarimetric
data is obtained and a complete model of the solar photosphere is
constructed. Automated SIR inversions of a HINODE data set were
performed and the output is compared to results of the MERLIN code,
another widespread inversion code in solar physics.
---------------------------------------------------------
Title: Centre to limb intensity variation of magnetic bright points
Authors: Utz, D.; Kühner, O.; Hanslmeier, A.; Veronig, A.; Muller,
R.; Lemmerer, B.; Pauritsch, J.; Thonhofer, S.
2012CEAB...36...17U Altcode:
The solar activity cycle is strongly related and rooted to photospheric
magnetic fields. Up to the present, it was mostly or even solely
studied by extended fields such as sunspots, sunspot groups or active
regions. Interestingly, the domain of magnetic fields on the Sun is
not only limited to extended and strong magnetic fields but reaches
down to small elements like single flux tubes. These flux elements
can be identified in G-band filtergrams as so called magnetic bright
points (MBPs). In this study we want to investigate the centre limb
variation of the mean MBP intensity for the period of the recent
solar minimum up to present (10/2008 - 10/2011). We found that a
4th order polynomial describes the centre limb variation fairly
well. Furthermore we established for the symmetrized and normalized
centre limb variation (for which the 1st and 3rd order parameter of
the polynomial is fixed to zero) a relationship between the 2nd and
4th order fit parameter. Hence it is possible to derive a description
with only one free parameter. Finally, we studied the variation with
time of this parameter for the period of October 2008 to present,
showing a slight increase and a weak correlation to solar activity as
given by the relative sunspot number.
---------------------------------------------------------
Title: Segmentation of Data from Simulations and Observations -
Evaluation and Outlook
Authors: Lemmerer, B.; Utz, D.; Hanslmeier, A.; Kühner, O.;
Grimm-Strele, H.; Pauritsch, J.; Thonhofer, S.; Muthsam, H.
2012CEAB...36...29L Altcode:
3D simulation models based on Magneto-hydrodynamics (MHD) and Radiation
hydrodynamics (RHD) equations give an insight into the evolution
of magnetic field lines and convective motions. A 2D segmentation
algorithm was applied to data of the Japanese/US/European space
mission Hinode and its solar optical telescope (SOT) as well as on
3D models of the numerical simulation code ANTARES in order to study
the solar granulation and evaluate the algorithm. As a next research
step, the development of a 3D segmentation algorithm, adapted to the
simulation models, is required for the purpose of extracting magnetic
and convective phenomena, which furthermore enable an exact tracing
of their evolution.
---------------------------------------------------------
Title: Non-Varying Granulation and Photospheric Network During the
Extended 2007 - 2009 Solar Minimum
Authors: Muller, R.; Utz, D.; Hanslmeier, A.
2011SoPh..274...87M Altcode:
We have analysed the wide band images taken by Hinode/SOT, in a blue
continuum window and in the G-band, more or less on a daily basis in
the frame of the synoptic program, to investigate the variation of the
solar granulation and of the photospheric network with the activity
cycle. A particular attention has been given to disentangle solar
effects from instrumental ones. It appears that a substantial fraction
of the images are more or less blurred and/or defocussed. During the
analysed period November 2006 - July 2010, the granulation contrast
of the sharpest selected images decreased steadily, the granulation
scale increased and the number of MBPs decreased (they are the Bright
Points of Magnetic origin which form the photospheric network in G-band
images). These trends are likely of instrumental origin. Consequently,
the granulation and the photospheric network have most probably not
changed during the extended solar minimum 2007 - 2009.
---------------------------------------------------------
Title: Impulsive Acceleration of Coronal Mass Ejections. I. Statistics
and Coronal Mass Ejection Source Region Characteristics
Authors: Bein, B. M.; Berkebile-Stoiser, S.; Veronig, A. M.; Temmer,
M.; Muhr, N.; Kienreich, I.; Utz, D.; Vršnak, B.
2011ApJ...738..191B Altcode: 2011arXiv1108.0561B
We use high time cadence images acquired by the STEREO EUVI and
COR instruments to study the evolution of coronal mass ejections
(CMEs) from their initiation through impulsive acceleration to the
propagation phase. For a set of 95 CMEs we derived detailed height,
velocity, and acceleration profiles and statistically analyzed
characteristic CME parameters: peak acceleration, peak velocity,
acceleration duration, initiation height, height at peak velocity,
height at peak acceleration, and size of the CME source region. The CME
peak accelerations we derived range from 20 to 6800 m s<SUP>-2</SUP>
and are inversely correlated with the acceleration duration and the
height at peak acceleration. Seventy-four percent of the events reach
their peak acceleration at heights below 0.5 R <SUB>sun</SUB>. CMEs that
originate from compact sources low in the corona are more impulsive and
reach higher peak accelerations at smaller heights. These findings can
be explained by the Lorentz force, which drives the CME accelerations
and decreases with height and CME size.
---------------------------------------------------------
Title: Multiwavelength Investigations of Magnetic Bright Points
Authors: Kühner, O.; Utz, D.; Hanslmeier, A.; Veronig, A.; Roudier,
T.; Muller, R.; Muthsam, H.
2011CEAB...35...29K Altcode:
In this contribution we present our results regarding the study
of small scale magnetic fields as seen by magnetic bright points
(MBPs) in different wavelengths and hence different heights. By the
determination of the size distribution of these features we are able
to derive the value of the scale height parameter for the photosphere:
107 km ± 18.5 km. For the Fe I line at 630.25 nm we derived a formation
height of 225 km.
---------------------------------------------------------
Title: Magnetic energy estimation for small scale magnetic fields
Authors: Utz, D.; Hanslmeier, A.; Veronig, A.; Kühner, O.; Muller,
R.; Muthsam, H.
2011CEAB...35...19U Altcode:
In this paper we derive an estimate of the energy content of small scale
magnetic <P />fields as observed by magnetic bright points (MBPs). For
our estimations we use as inputs the size, lifetime, magnetic field
strength of MBPs and the average number density of those features in the
quiet Sun. Furthermore we introduce an evolutionary model for MBPs. Our
results suggest that there is enough magnetic field energy stored in kG
fields as seen by MBPs to heat the chromosphere and corona. The actual
heating mechanism and process has to be investigated in the future.
---------------------------------------------------------
Title: Dynamika fotosférických jasných bodov v G-páse odvodená
použitím dvoch plne automatických algoritmov
---------------------------------------------------------
Title: Dynamika
fotosférických jasných bodov v G-páse odvodená použitím dvoch
plne automatických algoritmov
---------------------------------------------------------
Title: Dynamics of photospheric bright
points in G-band derived from two fully automated algorithms.
Authors: Bodnárová, M.; Rybák, J.; Hanslmeier, A.; Utz, D.
2010nspm.conf...25B Altcode:
Concentrations of small-scale magnetic field in the solar photosphere
can be identified in the G-band of the solar spectrum as bright
points. Studying the dynamics of the bright points in the G-band
(BPGBs) can also help in addressing many issues related to the
problem of the solar corona heating. In this work, we have used
a set of 142 specled images in the G-band taken by the Dutch Open
Telescope (DOT) on 19 October 2005 to make a comparison of two fully
automated algorithms identifying BPGBs: an algorithm developed by Utz
et al. (2009, 2010), and an algorithm developed following the work
of Berger et al. (1995, 1998). We then followed in time and space
motion of the BPGBs identified by both algorithms and constructed the
distributions of their lifetimes, sizes and speeds. The results show
that both algorithms give very similar results for the BPGB lifetimes
and speeds, but their results vary significantly for the sizes of the
identified BPGBs. This difference is due to the fact that in the case of
the Berger et al. identification algorithm no additional criteria were
applied to constrain the allowed BPGB sizes. As a result in further
studies of the BPGB dynamics we will prefer to use the Utz algorithm
to identify and track BPGBs.
---------------------------------------------------------
Title: Dynamics of isolated magnetic bright points derived from
Hinode/SOT G-band observations
Authors: Utz, D.; Hanslmeier, A.; Muller, R.; Veronig, A.; Rybák,
J.; Muthsam, H.
2010A&A...511A..39U Altcode: 2009arXiv0912.1965U
Context. Small-scale magnetic fields in the solar photosphere can
be identified in high-resolution magnetograms or in the G-band as
magnetic bright points (MBPs). Rapid motions of these fields can
cause magneto-hydrodynamical waves and can also lead to nanoflares by
magnetic field braiding and twisting. The MBP velocity distribution is
a crucial parameter for estimating the amplitudes of those waves and
the amount of energy they can contribute to coronal heating. <BR />
Aims: The velocity and lifetime distributions of MBPs are derived from
solar G-band images of a quiet sun region acquired by the Hinode/SOT
instrument with different temporal and spatial sampling rates. <BR
/> Methods: We developed an automatic segmentation, identification
and tracking algorithm to analyse G-Band image sequences to obtain
the lifetime and velocity distributions of MBPs. The influence of
temporal/spatial sampling rates on these distributions is studied and
used to correct the obtained lifetimes and velocity distributions for
these digitalisation effects. <BR /> Results: After the correction of
algorithm effects, we obtained a mean MBP lifetime of (2.50 ± 0.05)
min and mean MBP velocities, depending on smoothing processes, in
the range of (1-2) km~s<SUP>-1</SUP>. Corrected for temporal sampling
effects, we obtained for the effective velocity distribution a Rayleigh
function with a coefficient of (1.62 ± 0.05) km~s<SUP>-1</SUP>. The
x- and y-components of the velocity distributions are Gaussians. The
lifetime distribution can be fitted by an exponential function.
---------------------------------------------------------
Title: Investigating the Variation of the Solar Granulation with
HINODE Synoptic images
Authors: Muller, R.; Hanslmeier, A.; Utz, D.
2010CEAB...34...89M Altcode:
We have analysed the wide band images taken by HINODE/SOT on a daily
basis in the frame of the synoptic program, to investigate the variation
of the solar granulation with the activity cycle. A particular attention
has been given to disentangle solar from instrumental effects. It
appears that a substantial fraction of the images are more or less
blurred and/or defocused. The granulation contrast decrease and scale
increase of the sharpest images, observed during the period November
2006 - January 2009, is probably not of solar origin.
---------------------------------------------------------
Title: Multiwavelength alignment of Hinode/SOT Data
Authors: Kuehner, O.; Utz, D.; Hanslmeier, A.; Veronig, A.; Roudier,
T.; Muller, R.; Muthsam, H.
2010CEAB...34...31K Altcode:
First results regarding the spatial alignment of observations taken at
different wavelengths are presented. An exceptionally long time series
(48 hours) of data, obtained by the Solar Optical Telescope (SOT)
of the Hinode satellite, has been analysed. Hinode delivers (among
other data) high resolution seeing free filtergrams in the magnetic
sensitive G-band, blue continuum, chromospheric Ca II H line and Fe I
line. For the study of the position and dynamics of small scale fields
(MBPs; Magnetic Bright Points) at different wavelengths (at different
heights in the photosphere and chromosphere) the alignment of these
data at pixel and subpixel level will be essential. Results concerning
the height dependence of MBPs will also be of vital importance for
questions regarding the coronal heating.
---------------------------------------------------------
Title: G-band to Blue-Continuum Excess as quasi total field strength
magnetogram
Authors: Utz, D.; Hanslmeier, A.; Veronig, A.; Rybák, J.; Muller,
R.; Muthsam, H.
2010CEAB...34...13U Altcode:
The dynamics of the solar plasma is driven by strong localized magnetic
fields. It is well known that activity like flares and CMEs are related
to the dissipation and reconnection of these magnetic fields. These
energetic releases influence and make up the so called space weather. It
is therefore of vital importance to get a deeper understanding of the
magnetic fields of the Sun. To get this insights, it is crucial to
obtain information on the magnetic fields with spatial and temporal
resolutions as high as possible. In this paper we outline an easy to
apply method to obtain quasi total magnetic field strength magnetograms
out of two simple filtergrams (blue continuum and G-band). We will
present our simple approach and the first results of this method and
give finally an outlook what has to be done in the future.
---------------------------------------------------------
Title: Hinode - Synoptic observations of convection dynamics
Authors: Hanslmeier, A.; Muller, R.; Utz, D.; Roudier, T.
2010CEAB...34...81H Altcode:
The variation of solar convection over the solar activity cycle is
still discussed with controversial results. In this paper we study
the solar granulation and its variation over the unusual long lasting
solar minimum between cycle 23 and 24. Spatially highly resolved Hinode
images were segmented and the mean value of the segmented granules as
well as their number was found to be practically constant.
---------------------------------------------------------
Title: Magnetic field strength distribution of MBPs infered from
Hinode/SOT filtergram and spectro-polarimetric data
Authors: Utz, Dominik; Veronig, Astrid; Hanslmeier, Arnold; Muller,
Richard; Muthsam, Herbert
2010cosp...38.2944U Altcode: 2010cosp.meet.2944U
Small scale magnetic fields can be observed on the Sun in G-band
filtergrams as magnetic bright points (MBPs), or by inversions
of spectro-polarimetric data. In this study we used three
different data sets of Hinode/SOT observations which were recorded
simultaneously with the broadband filter device (G-band, Ca II-H) and
the spectro-polarimeter. The spectro-polarimetric data were already
prepared as magnetograms (level 2 data). For the identification of the
MBPs we used an automated identification algorithm. The three data sets
comprise active regions (a sunspot group and a small sunspot in the
other case) as well as quiet Sun. The obtained magnetic field strength
distribution of MBPs is in all three cases similar and shows a peaked
maximum at 1250 G, which agrees well with theoretical predictions of
the convectice collapse model.
---------------------------------------------------------
Title: Brightness profiles and size distributions of MBPs observed
in different heights by HINODE/SOT data
Authors: Kühner, Otmar; Veronig, Astrid; Utz, Dominik; Hanslmeier,
Arnold; Muthsam, Herbert; Muller, Richard; Roudier, Thierry
2010cosp...38.2948K Altcode: 2010cosp.meet.2948K
We study the characteristics of Magnetic Bright Points (MBPs)
observed at different wave-lenghts and hence different heights of
the photosphere and chromosphere. The data sets were obtained with
the Solar Optical Telescope (SOT) of the Hinode satellite. Hinode
delivers (among other data) high resolution seeing free filtergrams in
the blue continuum, the Fe I line, the magnetic sensitive G-band and
the chromospheric Ca II H line. Due to the small scale structure of
MBPs it was essential for our study to develop an algorithm for the
image co-alignment at subpixel level for the images taken at these
four wavelenghts. We studied an exceptionally long time series (48h)
and analyzed the brightness profiles and size distributions of MBPs
at different heights. The mean size of the features increases with
increasing height and shows an exponential behavior. We obtained the
scale height parameter of the photosphere to be 110 km.
---------------------------------------------------------
Title: Dynamics of G-band bright points derived using two fully
automated algorithms
Authors: Bodnárová, M.; Utz, D.; Rybák, J.; Hanslmeier, A.
2010CEAB...34...25B Altcode:
Small-scale magnetic field concentrations (∼ 1 kG) in the solar
photosphere can be identified in the G-band of the solar spectrum
as bright points. Study of the G-band bright points (GBPs) dynamics
can help us in solving several questions related also to the coronal
heating problem. Here a set of 142 G-band speckled images obtained
using the Dutch Open Telescope (DOT) on October 19, 2005 are used to
compare identification of the GBPs by two different fully automated
identification algorithms: an algorithm developed by Utz et al. (2009a,
2009b) and an algorithm developed according to papers of Berger et
al. (1995, 1998). Temporal and spatial tracking of the GBPs identified
by both algorithms was performed resulting in distributions of
lifetimes, sizes and velocities of the GBPs. The obtained results show
that both algorithms give very similar values in the case of lifetime
and velocity estimation of the GBPs, but they differ significantly
in case of estimation of the GBPs sizes. This difference is caused
by the fact that we have applied no additional exclusive criteria on
the GBPs identified by the algorithm based on the work of Berger et
al. (1995, 1998). Therefore we conclude that in a future study of the
GBPs dynamics we will prefer to use the Utz's algorithm to perform
identification and tracking of the GBPs in G-band images.
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Title: The size distribution of magnetic bright points derived from
Hinode/SOT observations
Authors: Utz, D.; Hanslmeier, A.; Möstl, C.; Muller, R.; Veronig,
A.; Muthsam, H.
2009A&A...498..289U Altcode: 2009arXiv0912.2637U
Context: Magnetic bright points (MBPs) are small-scale magnetic features
in the solar photosphere. They may be a possible source of coronal
heating by rapid footpoint motions that cause magnetohydrodynamical
waves. The number and size distribution are of vital importance in
estimating the small scale-magnetic-field energy. <BR />Aims: The
size distribution of MBPs is derived for G-band images acquired by the
Hinode/SOT instrument. <BR />Methods: For identification purposes, a new
automated segmentation and identification algorithm was developed. <BR
/>Results: For a sampling of 0.108 arcsec/pixel, we derived a mean
diameter of (218 ± 48) km for the MBPs. For the full resolved data set
with a sampling of 0.054 arcsec/pixel, the size distribution shifted
to a mean diameter of (166 ± 31) km. The determined diameters are
consistent with earlier published values. The shift is most probably
due to the different spatial sampling. <BR />Conclusions: We conclude
that the smallest magnetic elements in the solar photosphere cannot
yet be resolved by G-band observations. The influence of discretisation
effects (sampling) has also not yet been investigated sufficiently.
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Title: Discretization Effects on the Size Distribution of Magnetic
Bright Points
Authors: Utz, D.; Hanslmeier, A.; Muller, R.; Veronig, A.; Muthsam,
H.; Möstl, C.
2009CEAB...33...29U Altcode:
We developed an automated identification algorithm for magnetic bright
points to derive the size distribution of MBPs in a quiet region near
solar disc centre. For this purpose two different data sets from the
Hinode/SOT mission were used. The first data set had a pixel spatial
sampling of 0.108 arcsec/pixel, whereas the second data set had the full
achievable spatial sampling of 0.54 arcsec/pixel. We found, that the
size distribution shifted from a mean value of 218 km in diameter to
a smaller value of about 166 km in diameter when the spatial sampling
was higher. Therefore, we suggest that discretization effects play a
crucial role for the study of small scale features. How the shift of
the two distributions could be explained, and how a deeper insight
into the discretization problem could be gained, is discussed.
---------------------------------------------------------
Title: The Size Distribution of Magnetic Bright Points derived from
Hinode/SOT Observations
Authors: Utz, D.; Hanslmeier, A.; Muller, R.; Astrid, V.; Muthsam,
H.; Möstl, Ch.
2008ESPM...12.2.50U Altcode:
In our poster we will present our results regarding the size
distribution of Magnetic Bright Points (MBPs) in the solar
photosphere. <P />The data sets were obtained through the Solar Optical
Telescope (SOT) of the recent Hinode satellite. Hinode was launched
in autumn 2006 and delivers (among other data) high resolution seeing
free filtergrams in the magnetic sensitive G-Band. We analyzed two
different data sets (with different pixel resolutions) near disk
center in a network region of the quiet sun. The interesting outcome
is that the derived size distribution depends on the used pixel
resolution. Discretisation effects and physical implications on the
derived size distributions will be discussed.