EDP Sciences
Free Access
Issue
A&A
Volume 439, Number 2, August IV 2005
Page(s) 737 - 747
Section The Sun
DOI https://doi.org/10.1051/0004-6361:20053027


A&A 439, 737-747 (2005)
DOI: 10.1051/0004-6361:20053027

Size dependence of solar X-ray flare properties

M. Battaglia, P. C. Grigis and A. O. Benz

Institute of Astronomy, ETH Zentrum SEC, 8092 Zürich, Switzerland
    e-mail: battaglia@astro.phys.ethz.ch

(Received 8 March 2005 / Accepted 24 April 2005 )

Abstract
Non-thermal and thermal parameters of 85 solar flares of GOES class B1 to M6 (background subtracted classes A1 to M6) have been compared to each other. The hard X-ray flux has been measured by RHESSI and a spectral fitting provided flux and spectral index of the non-thermal emission, as well as temperature and emission measure of the thermal emission. The soft X-ray flux was taken from GOES measurements. We find a linear correlation in a double logarithmic plot between the non-thermal flux and the spectral index. The higher the acceleration rate of a flare, the harder the non-thermal electron distribution. The relation is similar to the one found by a comparison of the same parameters from several sub-peaks of a single flare. Thus small flares behave like small subpeaks of large flares. Thermal flare properties such as temperature, emission measure and the soft X-ray flux also correlate with peak non-thermal flux. A large non-thermal peak flux entails an enhancement in both thermal parameters. The relation between spectral index and the non-thermal flux is an intrinsic feature of the particle acceleration process, depending on flare size. This property affects the reported frequency distribution of flare energies.


Key words: Sun: flares -- Sun: X-rays, $\gamma$-rays -- acceleration of particles




© ESO 2005

Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.

Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.

Initial download of the metrics may take a while.