Millimeter and X-Ray Emission from the 5 July 2012 Solar Flare

Abstract

<p>The 5 July 2012 solar flare SOL2012-07-05T11:44 (11:39 – 11:49 UT) with an increasing millimeter spectrum between 93 and 140 GHz is considered. We use space and ground-based observations in X-ray, extreme ultraviolet, microwave, and millimeter wave ranges obtained with the <em>Reuven Ramaty High-Energy Solar Spectroscopic Imager</em>, <em>Solar Dynamics Observatory</em> (SDO), <em>Geostationary Operational Environmental Satellite</em>, <em>Radio Solar Telescope Network</em>, and <em>Bauman Moscow State Technical University millimeter</em> radio telescope RT-7.5. The main parameters of thermal and accelerated electrons were determined through X-ray spectral fitting assuming the homogeneous thermal source and thick-target model. From the data of the <em>Atmospheric Imaging Assembly</em>/SDO and differential-emission-measure calculations it is shown that the thermal coronal plasma gives a negligible contribution to the millimeter flare emission. Model calculations suggest that the observed increase of millimeter spectral flux with frequency is determined by gyrosynchrotron emission of high-energy (≳300 ≳300

keV) electrons in the chromosphere. The consequences of the results are discussed in the light of the flare-energy-release mechanisms.<br /></p>