Exploring Thermal and Non-Thermal Flare Emission with EVE and RHESSI
Abstract
Solar flares accelerate electrons up to hundreds of MeV and heat plasma to tens of MK, but the physical processes behind these phenomena remain poorly understood. In large (GOES M- and X-class) flares, in addition to the 10-25 MK plasma thought to be the result of chromospheric evaporation, even hotter plasma (up to 50 MK) may be directly heated in the corona. While observations of hard X-ray bremmstrahlung directly probe the non-thermal electron population, for large flares the spectra below 20-30 keV are typically dominated by this strong thermal emission. The low energy extent of the non-thermal spectrum can be only loosely quantified, resulting in significant implications for calculating flare energy budgets and for constraining possible acceleration mechanisms. A precise characterization of the non-thermal electron population requires an equally precise characterization of the thermal emission. Extreme ultraviolet observations from the EUV Variability Experiment (EVE) on-board the Solar Dynamics Observatory (SDO), combined with X-ray data from the Reuven Ramaty High Energy Spectroscopic Imager (RHESSI), currently offer the most comprehensive view of the flare temperature distribution. EVE observes EUV emission lines with peak formation temperatures of 2-20 MK, while RHESSI observes the X-ray bremsstrahlung of hot, 10-50 MK plasma; combined, the two instruments cover the full range of flare plasma temperatures. We have calculated differential emission measures (DEMs), using EVE and RHESSI independently, for a small number of flares. In this work we concentrate on comparing the observed DEM functions from EVE and RHESSI with each other, during different phases of flares, for the purpose of cross-calibration of the two instruments. When cross-calibration is successful, we will combine the data from the two instruments to create a DEM function for the temperature range up to 50 MK.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFMSH52B..02M
- Keywords:
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- 7509 SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY / Corona;
- 7514 SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY / Energetic particles;
- 7519 SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY / Flares;
- 7846 SPACE PLASMA PHYSICS / Plasma energization