Coronal structure of the Whole Sun Month: A tomographic reconstruction

Zidowitz, Stephan

doi:10.1029/1998ja900099

Cited by 34 publications

(19 citation statements)

References 21 publications

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“…Let us remark that the structure identification method by magnetic field lines provides already a 3D structure of the loop which might be further refined by stereoscopic methods. In particular, the advent of the STEREO mission has produced an increased interest of the solar physics community in stereoscopic (Aschwanden et al,1999 and tomographic techniques (Zidowitz, 1999;Frazin, 2000;Wiegelmann & Inhester, 2003) used in other branches of physics, image and information sciences. However, unlike many of the "experiments" conducted in the latter disciplines, the STEREO mission does not provide sufficient control over many of the parameters which determine the conditions for an optimal 3D reconstruction.…”

Section: Discussionmentioning

confidence: 99%

How To Use Magnetic Field Information For Coronal Loop Identification

et al. 2005

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Abstract. The structure of the solar corona is dominated by the magnetic field because the magnetic pressure is about four orders of magnitude higher than the plasma pressure. Due to the high conductivity the emitting coronal plasma (visible e.g. in SOHO/EIT) outlines the magnetic field lines. The gradient of the emitting plasma structures is significantly lower parallel to the magnetic field lines than in the perpendicular direction. Consequently information regarding the coronal magnetic field can be used for the interpretation of coronal plasma structures. We extrapolate the coronal magnetic field from photospheric magnetic field measurements into the corona. The extrapolation method depends on assumptions regarding coronal currents, e.g. potential fields (current free) or force-free fields (current parallel to magnetic field). As a next step we project the reconstructed 3D magnetic field lines on an EIT-image and compare with the emitting plasma structures. Coronal loops are identified as closed magnetic field lines with a high emissivity in EIT and a small gradient of the emissivity along the magnetic field.

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Section: Discussionmentioning

confidence: 99%

How To Use Magnetic Field Information For Coronal Loop Identification

et al. 2005

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“…This model was further developed by Gibson et al (2003) to include more complex structures, in particular streamers at mid-latitude. Uninterrupted observations of the solar corona over the course of half a rotation or longer has made solar rotational tomography possible (Davila 1994;Zidowitz 1999;Frazin 2000, for example). These tomographic reconstructions have concentrated on the solar minimum corona.…”

Section: Introductionmentioning

confidence: 99%

An empirical 3D model of the large-scale coronal structure based on the distribution of Hα filaments on the solar disk

Morgan¹,

Habbal²

2006

A&A

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Context. Despite the wealth of solar data currently available, the explicit connection between coronal streamers and features on the solar disk remains unresolved. Aims. To reproduce the large-scale coronal structure starting from the solar surface, an empirical three-dimensional (3D) model is used to test the assumption that such structure, namely streamers, is a consequence of twisted high-density sheets originating from prominences (or, equivalently, filaments) at the base of the corona. Methods. A 3D model is created whereby high-density sheets are placed above filaments on the solar disk, which twist and merge with height into a final radial configuration constrained by the oberved position of streamers stalks higher up in the corona. Results. The 3D model thus derived yields a reasonable agreement with the observed large-scale coronal structure, in particular the shape of large helmet streamers. Conclusions. These results give confidence in the underlying assumption that large helmet streamers can be the result of the convergence of two or more sheet-like structures originating from a distribution of filaments on the solar disk. The model supports the view that streamers, during that time of the solar cycle, are often associated with multiple current sheets.

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“…The Solar TErrestrial RElations Observatory (STEREO), now being assembled and planned for launch in November 2005, will be the first true stereoscopic facility, mapping the Sun with an increasing separation angle of 22 • per year. Alternative approaches of 3D reconstruction methods utilize the solar rotation to vary the aspect angle (Altschuler 1979;Berton & Sakurai 1985;Koutchmy & Molodensky 1992;Aschwanden & Bastian 1994a,b;Batchelor 1994;Hurlburt et al 1994;Zidowitz 1999;Koutchmy, Merzlyakov, & Molodensky 2001), but this method generally requires static structures over several days. An advanced form of solar rotation stereoscopy is the so-called dynamic stereoscopy method (Aschwanden et al 1999(Aschwanden et al , 2000a, where the 3D geometry of dynamic plasma structures can be reconstructed as long as the guiding magnetic field is quasi-stationary.…”

Section: Introductionmentioning

confidence: 99%

Tomographic 3D-Modeling of the Solar Corona with FASR

Aschwanden¹,

Alexander

Rosa³

2004

Solar and Space Weather Radiophysics

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Abstract. The Frequency-Agile Solar Radiotelescope (FASR) litteraly opens up a new dimension in addition to the 3D Euclidian geometry: the frequency dimension. The 3D geometry is degenerated to 2D in all images from astronomical telescopes, but the additional frequency dimension allows us to retrieve the missing third dimension by means of physical modeling. We call this type of 3D reconstruction Frequency Tomography. In this study we simulate a realistic 3D model of an active region, composed of 500 coronal loops with the 3D geometry [x(s), y(s), z(s)] constrained by magnetic field extrapolations and the physical parameters of the density ne(s) and temperature Te(s) given by hydrostatic solutions. We simulate a series of 20 radio images in a frequency range of ν = 0.1 − 10 GHz, anticipating the capabilities of FASR, and investigate what physical information can be retrieved from such a dataset. We discuss also forward-modeling of the chromospheric and Quiet Sun density and temperature structure, another primary goal of future FASR science.

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Coronal structure of the Whole Sun Month: A tomographic reconstruction

Cited by 34 publications

References 21 publications

How To Use Magnetic Field Information For Coronal Loop Identification

How To Use Magnetic Field Information For Coronal Loop Identification

An empirical 3D model of the large-scale coronal structure based on the distribution of Hα filaments on the solar disk

Tomographic 3D-Modeling of the Solar Corona with FASR

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