A ring of polarized light: evidence for twisted coronal magnetism in cavities (Invited)
Abstract
Determining coronal magnetic fields is crucial to modeling the processes that power and trigger solar flares and coronal mass ejections. Coronal prominence cavities have been modeled as magnetic flux ropes, and have been observed to erupt bodily as coronal mass ejections. One promising technique for establishing the magnetic morphology of cavities is to use spectropolarimetry of the infrared (IR) forbidden lines of Fe XIII (at 1074.7 nm and 1079.8 nm). The Coronal Multi-Channel Polarimeter is currently situated at the Mauna Loa Solar Observatory (MLSO), and has begun taking daily full-Sun observations of line-of-sight integrated Stokes parameters for these lines. For a variety of analytic coronal magnetohydrodynamic models, we have determined forward-calculations of CoMP observables using the formalism of Judge and Casini (2001). We show that different MHD models and orientations do yield distinguishing observational characteristics. In particular, a common characteristic for spheroidal flux ropes oriented along the observational line of sight is a ring of linear polarization surrounding a region where the linear polarization strength is relatively depleted (the heart of darkness). Such a polarization ring has been found in an observation of a coronal cavity taken by CoMP in April 2005 from Sacramento Peak. Cavities are ubiquitous features, particularly at this time of the solar cycle. The daily observations to be taken by CoMP at MLSO will allow us to further probe these structures, constraining models of coronal magnetism and providing a testbed for future capabilities of the proposed Coronal Solar Magnetism Observatory (COSMO).
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFMSH54A..01D
- Keywords:
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- 7509 SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY / Corona;
- 7513 SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY / Coronal mass ejections;
- 7524 SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY / Magnetic fields;
- 7531 SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY / Prominence eruptions