Modern Solar Facilities
Advanced Solar Science, Proceedings of a Workshop held at Göttingen, September 27-29, 2006
Publication Year: 2010
Published by: The University of Akron Press
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Summary of the workshop
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An international workshop entitled: ‘Modern Solar Facilities – Advanced Solar Science’ was held in Göttingen from 27 to 29 September, 2006. It took place in the new physics building located in the northern campus of the Georg-August-Universität. The workshop was attended by 88 participants from 24 different countries (see the list of participants, pp. 375–381, containing the institutional addresses at the time of the workshop). ...
1. Telescopes and instrumentation
Future solar space missions (invited)
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Abstract. The coming years promise to be the golden era of solar and heliospheric physics, with STEREO, Hinode (Solar-B) and SDO enhancing the current fleet of solar space missions and affording new opportunities for improved understanding of the Sun-heliosphere system. Looking beyond that, however, there is a significant gap until Solar Orbiter will be launched in 2015 (nearly 20 years after the launch of SOHO). ...
LYRA - a solar UV radiometer using diamond detectors
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Abstract. LYRA, the Lyman-α radiometer, is a high–cadence (100 Hz) solar VUV radiometer which will measure disk–integrated irradiances in 4 wavelength channels. Special emphasis is given on novel detectors based on diamond which will be tested for the first time in space. ...
Ground-based solar facilities in the U.S.A. (invited)
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Abstract. In this review, we present the status of new ground-based facilities for optical and radio observations of the Sun in the United States. The 4-meter aperture Advanced Technology Solar Telescope (ATST) under the stewardship of the National Solar Observatory (NSO) has successfully completed its design phase and awaits funding approval. ...
New high resolution solar telescope GREGOR (invited)
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Abstract. The 1.5 m solar telescope GREGOR is being constructed at Tenerife, Spain. Its purpose is to observe with high spatial and spectral resolution small-scale dynamic magnetic features on the Sun. The telescope is completely open with retractable dome and actively cooled primary mirror made of silicon carbide to minimize thermal effects on the image quality. ...
From the “Göttingen” Fabry-Perot Interferometer to the GREGOR FPI
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Abstract. Fabry-Perot Interferometers (FPIs) have advantages over slit spectrographs, allowing fast two-dimensional, narrowband imaging and post factum image reconstruction of the spectropolarimetric data obtained. The resulting intensity, velocity and magnetic field maps are a fundamental base for the understanding of the dynamics of the solar atmosphere and its magnetic fields at smallest spatial scales. ...
Gregor@Night. A concept for a night-time spectrograph for the 1.5m solar telescope GREGOR
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Abstract. Gregor@Night is the concept for a fiber-fed double echelle spectrograph for the night-time use of GREGOR. Its design specifications are driven by a science case based on the solar-stellar connection, ranging from the search and characterization of solar analogs, the characterization of late-type stars...
Multi-wavelength observations at the German VTT on Tenerife – Possible combinations of post-focus instruments
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Abstract. To study the small-scale dynamic processes of magneto-convection in the solar photosphere in more detail than currently achieveable, not only the spatial resolution has to be increased, but also the information content of observations. In order to do so, several wavelengths and spectral lines must be observed simultaneously. ...
Instrumental developments at the Gregory Coude Telescope (GCT) at IRSOL
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Abstract. The research projects carried out with the Gregory Coudé Telescope (GCT) at Istituto Ricerche Solari Locarno (IRSOL) are mainly focused on high precision polarimetry. The Zurich IMaging POLarimeter (ZIMPOL) developed at ETH Zurich and installed permanently at the GCT at IRSOL allows a polarimetric precision down to 10−5 to be reached. ...
Imaging polarimetry with a tunable narrow-band filter
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Abstract. We have developed a fully tunable narrow-band filter system to be used in combination with ZIMPOL for monochromatic imaging vector polarimetry. It is designed for the whole visible spectrum, from the UV at about 395 nm, to the red at about 660 nm, with a band width of 30–50 mÅ. ...
Methods in high-resolution solar spectroscopy
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Abstract. After few historical remarks, the needs in high-resolution spectroscopy are outlined. They are concerned with temporal, spatial, and wavelength resolution for a reasonable field of view of supergranulation cell or larger. At 0′.′1 spatial resolution (≈ˆ72.5km on the Sun) the measurement for a...
SUNRISE: High resolution UV/VIS observations of the Sun from the stratosphere (invited)
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Abstract. SUNRISE is an international project for the development, construction, and operation of a balloon-borne solar telescope with an aperture of 1 m, working in the UV/VIS spectral domain. The main scientific goal of SUNRISE is to understand the structure and dynamics of the magnetic field in the atmosphere of the Sun. ...
ZERODUR mirror substrates for solar telescopes
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Abstract. The zero-expansion glass ceramic material, ZERODUR, is well known for nighttime telescope mirror substrates. Also for solar telescopes, ZERODUR is often selected as mirror blank material. ...
2. High-resolution and high-precision observations
Future missions for helioseismology (invited)
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Abstract. In this paper I provide basic information on the scientific objectives of upcoming helioseis- mology missions. The launch of NASA’s Solar Dynamics Observatory (SDO) in 2008 is an important opportunity for helioseismology. SDO will carry the Helioseismic and Magnetic Imager (HMI), which will have a 1′′ resolution over the whole visible solar...
Helioseismology at MPS
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Abstract. Research in solar and stellar seismology at the Max Planck Institute for Solar System Research (MPS) is supported by the Junior Research Group “Helio- and Asteroseismology” of the Max Planck Society since September 2005. A presentation of the current topics of research is given, with particular emphasis on local helioseismology. ...
Structure and evolution of supergranulation from local helioseismology
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Abstract. Maps of the horizontal divergence of the near-surface velocity field have been calculated using local helioseismology and SOHO/MDI full-disk Dopplergrams. These maps provide a continuous coverage for two to three months each year with a cadence of 12 hours. ...
Solar adaptive optics (invited)
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Abstract. We give an overview of solar adaptive optics (AO) systems, its differences to nighttime AO systems and some basic design considerations for the wavefront sensor and the wavefront reconstruction. As an example, we present the Kiepenheuer Adaptive Optics System (KAOS), lessons learned from four years of operation, and the various...
Anisoplanatic optical transfer functions for solar adaptive optics from simulation using wave front sensor data
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Abstract. Solar observations with online compensation of atmospheric seeing is possible at the Vacuum Tower Telescope (VTT) on Tenerife (Spain) with the aid of the Kiepenheuer Adaptive Optics (AO) System Kaos. For the post-facto speckle image reconstruction methods used at our institutes, however, problems arise regarding...
Solar image restoration (invited)
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Abstract. Image restoration is used to repair solar images degraded by the turbulence in Earth’s atmosphere. Restoration algorithms are based on models of the optical system that produce the images – from the solar source of radiation, through Earth’s atmosphere and telescope/instrument optics, to the detectors recording the data. ...
Probabilistic suppression of astronomical image degradations
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Abstract. A multichannel fast adaptive recursive restoration method based on the underlying spatial probabilistic image model is presented. The method assumes a linear degradation model with the unknown, possibly non-homogeneous point-spread function, and additive noise for each of mutually registered degraded observations. ...
Advances, challenges and limitations of speckle reconstruction and deconvolution
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Abstract. This paper presents the experiences with speckle imaging and deconvolution techniques we have made during the last five years at the Kiepenheuer-Institut f
Reversed granulation in Fe I 7090.4
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Abstract. The reversal of the photospheric continuum intensity pattern is predicted by numerical simulations and has been observed in the wings of chromospheric lines. Here we present reversed granulation extracted from the photospheric Fe i 7090.4 Å line core intensities, after taking into ac- count the velocity effects, in high spatial, spectral and temporal resolution. ...
The height dependence of temperature – velocity correlation in the solar photosphere
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Abstract. We derive correlation coefficients between temperature and line-of-sight velocity as a function of optical depth throughout the solar photosphere for the non-magnetic photosphere and a small area of enhanced magnetic activity. ...
Polarimetry in the visible and near infrared (invited)
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Abstract. The various techniques used in the visible and near-infrared for the measurement of intrinsic polarization coming from solar regions are described. Their performance to allow for the acquisition of simultaneous spectropolarimetric data at several wavelengths is discussed. ...
Dynamics of the quiet photosphere and its magnetic field under high spatial resolution
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Abstract. An excellent 1 h 10 min time series of a quiet solar region near disk centre was acquired on 4th of May 2006 at the German Vacuum Tower Telescope. Using the new “Göttingen” Fabry- Perot interferometer together with the Kiepenheuer Adaptive Optics system spectropolarimetric images were obtained, scanning the Fe i 5247 Å and Fe i 5250 Å lines with a temporal cadence of 17 s each. ...
Internetwork magnetic fields
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Abstract. Spectropolarimetric observations of the internetwork obtained in the 1.56 μm Fe i doublet are used to calculate the distributions of magnetic field strength, filling factor and magnetic flux density at different positions on the solar surface. ...
High-resolution CN spectroscopy of small-scale solar magnetic features
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Abstract. High-resolution spectroscopic observations of small-scale magnetic elements in the solar photosphere were carried out in the spectral region 387.5–388.4 nm with the 1-m Swedish Solar Telescope (SST). This part of the spectrum covers not only the violet CN band-head, but also contains some lines of the CH molecule. ...
Magnetic properties of G-band bright points
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Abstract. Bright points (BPs) visible in the G band at 430 nm are commonly used as tracers of magnetic fields, indicating the location of kG flux concentrations. To study the actual magnetic properties of G-band BPs, we took observations in 2003 and 2005, employing simultaneously a speckle setup in the G band and vector spectropolarimetry to derive the magnetic field vector. ...
Photospheric magnetic field and chromospheric emission
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Abstract. We present a statistical analysis of network and internetwork properties in the photosphere and the chromosphere. For the first time we simultaneously observed (a) the four Stokes parameters of the photospheric iron line pair at 630.2 nm and (b) the intensity profile of the Ca H line at 396.8 nm. The vector magnetic field was inferred from the inversion of the iron lines. ...
Velocity distribution of chromospheric downflows
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Abstract. Infrared spectropolarimetric observations were obtained with the Tenerife Infrared Polarimeter (TIP) at the German Vacuum Tower Telescope (VTT) of the Spanish observatory of Iza
Off-limb spectroscopy of the He I 10830
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Abstract. Spectropolarimetric observations of spicules were carried out with the new optical setup of the Tenerife Infrared Polarimeter (TIP 2) at the VTT, showing the variation of the He i 10830 Å multiplet off-limb emission profiles with increasing distance to the solar visible limb. ...
Study of polar faculae with north pole coverage of the Sun
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Abstract. We present here a description of the main characteristics of faculae at the poles of the Sun (polar faculae – PFe) observed in a series of observations covering the north solar pole. Statistics of a group of these PFe are used to estimate the contrast behaviour from μ = 0.6 towards the limb as well...
Effects of the “false” magnetic-field imbalance in solar active regions
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Abstract. The imbalance of magnetic fluxes of opposite polarities in solar active regions (ARs) is investigated. On the base of a topological magnetic-field model, we reveal some causes leading to the observations of the imbalance even if real magnetic fluxes are balanced. ...
Magnetic source of the solar cycle variation of the Mn I 539.4 nm line
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Abstract. As a part of the long term program at KPNO, the Mn I 539.4 nm line has been observed for nearly three solar cycles using the McMath telescope and the 13.5 m spectrograph in double pass mode. These full-disk spectrophotometric observations revealed an unusually large amplitude change...
Reconstruction of irradiance from 2D magnetograms and modification of the 1/
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Abstract. The key to understanding total Solar Irradiance (SI) variability is understanding the mechanisms by which continuum contrast is affected by the distribution of magnetic flux across the surface of the Sun. ...
Variations in solar indices during the 23rd solar cycle
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Abstract. The 23rd solar cycle is investigated using 6 different activity indices. The variations and comparisons of these indices are presented, and the dates of beginning, first, second maximum, and minimum between maxima are calculated to see how the cycle behaves in each index. ...
Structure and flattening of the solar corona
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Abstract. In this work, preliminary results of the investigation of the white-light coronal structure and the measurement of flattening parameters are presented. They were obtained using photographic eclipse observations performed during the total solar eclipse of March 29, 2006, in Ilıca, Antalya, ...
Fine structure in a dark umbra
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Abstract. An excellent-quality time series of images of a large dark umbra of the leading sunspot of NOAA 10634 was acquired on 18 June 2004 with the 1-m Swedish Solar Telescope at La Palma, simultaneously in blue, red, and G-band channels. ...
Dynamics of a solar pore with light bridge
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Abstract. Pores are one of numerous features formed by the emerging of magnetic field from the solar surface. Their uniqueness derives from the fact that – as far as size is concerned – they lie between the tiny flux tubes associated with magnetic elements, and the complex and large magnetic regions associated with sunspots. ...
Ca II H line wing images of sunspot penumbrae recorded with the Swedish 1-m Solar Telescope
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Abstract. We present recent Ca II H images of sunspot penumbrae taken with the Swedish 1 m Solar Telescope (SST) during June-July 2006 and restored to a resolution close to 0′.′1. Images were recorded at different Ca II H line positions using one tunable filter, one fixed wing filter and a wide band quasi-continuum...
Temporal evolution of intensity, velocity and magnetic field of sunspots at high spatial resolution
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Abstract. We present results of sunspot observations obtained in April 2006 with the new ’Göttingen’ Fabry-Perot spectrometer. Thanks to the large field of view (77′′ × 58′′ ) of the new optical setup it has been possible to perform 2D-spectropolarimetric observations of a small sunspot and ist surroundings...
Magnetic vector field above a sunspot
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Abstract. We present an analysis of the spectro-polarimetric measurements of the active region NOAA 10886 taken with the Tenerife Infrared Polarimeter in the Fe I 10783 Å spectral line. The magnetic field strength and the magnetic inclination and azimuth were inferred from the data using the inversion code...
The observational counterpart of the rising flux tube model?
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Abstract. An analysis of Stokes observations of a penumbra in active region NOAA 8990 is presented. The observations were recorded with the La Palma Stokes Polarimeter attached to the 1-m Swedish Solar Telescope. ...
Simultaneous polarimetric observations with VTT and THEMIS
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Abstract. Spectro-polarimetric observations of sunspot groups have been performed simultaneously with the VTT and with THEMIS. At the VTT we observed a group of iron and silicon lines at 1078 nm with the Tenerife Infrared Polarimeter, and at THEMIS we observed in five spectral channels (MTR-...
On the inhomogeneities of the sunspot penumbra
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Abstract. The penumbra is ideally suited to challenge our understanding of magnetohydrodynamics. The energy transport takes place as magnetoconvection in inclined magnetic fields under the effect of strong radiative cooling at the surface. ...
Modified p-modes in penumbral filaments
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Abstract. A time series analysis was performed on velocity signals in a sunspot penumbra to search for possible wave modes. The spectropolarimetric photospheric data obtained by the Tenerife Infrared Polarimeter were inverted using the SPINOR code. ...
Wave propagation and shock formation in diverse magnetic structures
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Abstract. Velocity oscillations measured simultaneously at the photosphere and the chromosphere of different solar magnetic features (sunspots, pores and facular regions) allow us to study the properties of wave propagation as a function of the magnetic flux of the structure. ...
Evolution of coronal hole boundaries seen in EIT 195
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Abstract. We aim at studying the spatial and temporal scales of the small-scale evolution of coronal hole boundaries using EUV observations from TRACE (171 Å) and EIT (195 Å) on-board SoHO with a spatial resolution of 1′′ and 5.5′′, respectively, and various time cadences. ...
Magnetic field structure and dynamics in coronal hole - active region interface zone
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Abstract. We study the changes of magnetic field structure in active regions (AR), coronal holes (CH), and coronal hole - active region (CH-AR) interface zones. Zones of coronal hole - active region interface are characterized by relatively fast fluctuations of the photospheric magnetic fields. ...
Evolution of the photospheric magnetic field in the source regions of coronal mass ejections
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Abstract. Six coronal mass ejections associated with erupting quiescent filaments on the visible solar disk were identified in data from SoHO (Solar and Heliospheric Observatory) LASCO (Large Angle and Spectrometric Coronagraph), EIT (Extreme ultraviolet Imaging Telescope) and MDI (Michelson...
Two-dimensional imaging of the HeD3/Hβ emission ratio in quiescent solar prominences
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Abstract. We extend our earlier studies of two-dimensional prominence imaging by simultaneous observations of the He D3 and Hβ emissions at the 1 m SST on La Palma. The observed small spatial variations of the He D3 /Hβ ratio indicate rather homogeneous physical conditions within prominences. ...
Wavelet-based method for coronal loop oscillations analysis
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Abstract. We study the properties of Doppler shift oscillations observed in hot coronal loops by SoHO/SUMER. These oscillations have been identified as magnetoacoustic slow mode standing waves and may be an important magnetic field diagnostic for the oscillating loops. ...
Magnetic stereoscopy of coronal loops in NOAA 8891
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Abstract. We present an application of the magnetic stereoscopy tool to the coronal loops observed by TRACE in the active region NOAA 8891. Designed for the newly launched STEREO mission, this tool aims to reconstruct the 3D geometry of coronal loops. ...
Observations of a flaring active region in Hα
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Abstract. A 40 min time series of the active region NOAA AR10875 was obtained on April 26th, 2006 under very good seeing conditions using the new “Götingen” Fabry-Perot interferometer at the German Vacuum Tower Telescope, Observatorio del Teide, Tenerife. ...
On the thermal and non-thermal excitation effects as studied in the Hα, Hß and Ca π 8542 Å line profiles in a solar flare
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Abstract. Spectral observations of the 26 June 1999 flare (Kotrč et al. 2004) presented a unique opportunity to compare effects of thermal and non-thermal mechanisms of excitation on profiles of Balmer series and Ca ii 8542 Å lines. ...
Solar HXR- and γ-ray emission measurements in 2005 by SONG/CORONAS-F near minimum of the last activity cycle
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Abstract. The Russian solar observatory CORONAS-F (Complex ORbital Observations in Near-Earth space of the Activity of the Sun) was launched on July 31, 2001 into an orbit with inclination 82.5
3. Theory and interpretation
Inversion techniques: From observations to atmospheres (invited)
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Abstract. Inversion techniques are presently the most powerful tools to deduce magnetic, dynamic, and thermal properties of the solar plasma from polarization line profiles. The reliability and robustness of Stokes inversions have been confirmed many times by means of numerical tests. ...
Stokes profile inversion in Meso-Structured Magnetic Atmospheres
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Abstract. Based on the Meso-Structured Magnetic Atmosphere (MESMA) approximation (Carroll & Kopf 2007) we present first results of an inversion of spectropolarimetric observations obtained from internetwork regions. ...
Line ratio method applied to inter-network magnetic fields
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Abstract. We investigate the validity of the Stokes V amplitude ratio as an indicator of the magnetic field strength in solar inter-network regions with the help of MHD simulations. We show that the Stokes V amplitude ratio of the Fe I 15652-15648 Å lines and Fe I 5247-5250 Å lines show a good correlation...
The Ba II λ4554 resonance line and solar granulation
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Abstract. We present the results of an investigation of the impact of NLTE effects and of granulation inhomogeneities on the solar Ba ii λ4554 Å line. Our analysis is based on both the classical one-dimensional (1D) solar atmosphere models and on the new generation of three-dimensional (3D)...
Magnetic mappers of the quiet solar atmosphere
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Abstract. The magnetic sensitivity of the solar spectrum is caused by the Zeeman effect and by a variety of less familiar physical mechanisms by means of which a magnetic field can create and destroy spectral line polarization. ...
Molecular Hanle effect in the Paschen-Back regime: theory and application
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Abstract. The second solar spectrum resulting from coherent scattering is a main tool for diagnostics of turbulent magnetic fields on the Sun. Scattering on diatomic molecules plays an important role in forming this spectrum and even dominates in some spectral regions. ...
Recent progresses in the simulation of small-scale magnetic fields (invited)
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Abstract. New high-resolution observations reveal that small-scale magnetic flux concentrations have a delicate substructure on a spatial scale of 0.1′′. Its basic structure can be interpreted in terms of a magnetic flux sheet or tube that vertically extends through the ambient weak-field or field-free at-...
Solar mesogranulation as a cellular automaton effect
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Abstract. We present a simple cellular automaton model of solar granulation that captures the granular cell characteristics in terms of lifetime and size distributions. We show that mesogranulation, as defined in observational data, is an intrinsic feature of such a cell system. ...
Sunspot models with bright rings
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Abstract. A theoretical sunspot model is provided including magnetic suppression of the diffusivities and also a strong stratification of density and temperature. Heat diffusion alone with given magnetic field and zero mean flow only produces (after a very long relaxation time) dark spots without any...
Numerical modeling of MHD wave propagation in sunspots: a 3D case
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Abstract. We present the first results of a 3D numerical modeling of linear MHD wave propagation in a realistic sunspot model. In our simulations, a piston located at the base of the photosphere generates waves with a certain period. ...
Seismology of sunspot atmosphere: from chromospheric resonance to nonlinear antireflection
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Abstract. The theory of 3-min oscillations in sunspot chromospheres is revised. Linear and nonlinear effects are taken into account. It is revealed that not only the chromospheric resonance is responsible for...
Ray tracing of ion-cyclotron waves in a coronal funnel
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Abstract. Remote observations of coronal holes have strongly implicated the kinetic interactions of ion-cyclotron waves with ions as a principal mechanism for plasma heating and acceleration of the fast solar wind. ...
Nanoflare model of emission line radiance distributions in active region coronae
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Abstract. Nanoflares are small impulsive bursts of energy that blend with and possibly make up much of the solar background emission. Determining their overall contribution is central to understanding the heating of the solar corona. ...
Modeling large-scale coronal structures
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Abstract. Current measurements provide the photospheric magnetic field (e.g., from MDI on SOHO) and line-of-sight integrated 2D coronal images (e.g., EIT). Our aim is to use these observations to...
Magnetic flux transport and the lifetimes of spots on active cool stars
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Abstract. We present results of numerical simulations of magnetic flux transport on the surfaces of cool stars with radii of 1 R⊙ and 3.3 R⊙. The effects of differential rotation and the tilt angle on the lifetimes of stellar bipolar magnetic regions are discussed. ...
Mass loss rates and wind ram pressures of cool stars
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Abstract. The stellar mass loss rate is important for the rotational evolution of a star and for its interaction with the circumstellar environment. Based on empirical mass loss rates of cool stars, we...
List of participants
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Page Count: 382
Illustrations: 20 line drawings, 278 graphs, 252 photos
Publication Year: 2010