Investigating Coronal Activity by Release Using Sublimation
Abstract
Plasma tails left by sun-grazing comets are visible in EUV, expanding their traditional role as "windsocks" into the low corona and serving as natural "chemical release" experiments. SDO obtained spectrally resolved video imagery of passages as close as 0.15 Rs to the solar photosphere at 12 sec frame cadence. Vaporized cometary materials form sublimation trails or "subtrails" that persist as long as 20 min. in 13.1 and 17.1 nm channels. Striation along local magnetic flux tubes implies filamentation of the visible plasma, and the subtrails exhibit substantial deviations from the comet orbital track. These reveal coronal winds and shears with velocities that are comparable to the comet velocity of up to 600 km/s. We analyze the likely origins and directionality of these winds and their implications for coronal heating in the altitude range where ion-neutral collision mean free paths are longer than the gyro radius but shorter than the atmospheric scale height, that is, the solar transition region. With active impact or photo-ionization, and charge exchange, the inferred super-thermal, sub-Alfvenic ion-neutral relative velocities will lead to ion pick-up distributions that decay or relax into "kappa" distributions with super-thermal power law tails that are relevant to the formation of the corona.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFMSH21D..05M
- Keywords:
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- 7509 SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY / Corona;
- 7546 SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY / Transition region;
- 7594 SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY / Instruments and techniques