Physical Conditions in the Source Region of a Zebra Structure

Abstract

We analyze the physical conditions in the source region of a zebra structure, observed with the Ondřejov radiospectrograph during the 1 August 2010 solar flare. To determine the gyro-frequency harmonic numbers of the observed zebra lines, we compute the magnetic field strength, the electron density, and their spatial scales in the source region of the zebra structure. The region where the flare occurred is analyzed using EUV (171 A and 335 A) observations. To determine the conditions in the zebra source region, the magnetic field structure is reconstructed using observed photospheric magnetic field data. By computing the dependence of the magnetic field vs. height in this reconstruction and by comparing the magnetic field strength derived from the zebra structure, we determine the dependence of the electron density vs. height in the zebra source-region. We identify the loops where the zebra structure was generated at heights of about 2.5 – 3.3 Mm. Assuming the barometric law for the electron density, we determine the temperature in the zebra source-region to be \(T \approx 2.0 \times 10^{4}~\mbox{K}\). Comparing the obtained values of the temperature and electron density in the zebra source-region with a model of the solar atmosphere, we find that the zebra structure was generated in the transition region, in agreement with our previous results.