Multithermal Representation of the Kappa-distribution of Solar Flare Electrons and Application to Simultaneous X-Ray and EUV Observations
Abstract
Acceleration of particles and plasma heating is one of the fundamental problems in solar flare physics. An accurate determination of the spectrum of flare-energized electrons over a broad energy range is crucial for our understanding of aspects such as the acceleration mechanism and the total flare energy. Recent years have seen a growing interest in the kappa-distribution as a representation of the total spectrum of flare-accelerated electrons. In this work we present the kappa-distribution as a differential emission measure. This allows for inferring the electron distribution from X-ray observations and EUV observations by simultaneously fitting the proposed function to RHESSI and SDO/AIA data. This yields the spatially integrated electron spectra of a coronal source from less than 0.1 keV up to several tens of keV. The method is applied to a single-loop GOES C4.1 flare. The results show that the total energy can only be determined accurately by combining RHESSI and AIA observations. Simultaneously fitting the proposed representation of the kappa-distribution reduces the electron number density in the analyzed flare by a factor of ∼30 and the total flare energy by a factor of ∼5 compared with the commonly used fitting of RHESSI spectra. The spatially integrated electron spectrum of the investigated flare between 0.043 and 24 keV is consistent with the combination of a low-temperature (∼2 MK) component and a hot (∼11 MK) kappa-like component with spectral index 4, reminiscent of solar wind distributions.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 2015
- DOI:
- 10.1088/0004-637X/815/1/73
- arXiv:
- arXiv:1511.01328
- Bibcode:
- 2015ApJ...815...73B
- Keywords:
-
- acceleration of particles;
- Sun: corona;
- Sun: flares;
- Sun: X-rays;
- gamma rays;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 24 pages, 7 figures, ApJ, accepted