Simulations of solar radio zebras

Abstract

Context.Solar radio zebras are used in diagnostics of solar flare plasmas and it is of great importance to construct accurate models to correctly characterize them.Aims.We simulated two zebras to verify their double-plasma resonance (DPR) model.Methods.In our zebra simulations, we used the DPR model in an expanding and compressing part of the loop as well as with the wave propagating along the loop.Results.Using the DPR model in such a loop, we successfully simulated zebras from the 1 August 2010 and 21 June 2011 flares. We found that increasing the density or decreasing the magnetic field in the part of the loop, where zebra-stripe sources are located, the zebra stripes are shifted to higher frequencies and vice versa. In the case of the 21 June 2011 flare, we confirm that small deviations of zebra-stripe frequencies from their mean values can be explained by waves propagating along the loop. We also confirm high values for the gyro-harmonic number of zebra stripes. We explain an inconsistency in the wave velocities derived from the plasma parameters and from the frequency drift in combination with the density model of the solar atmosphere. Finally, we discuss the high values of the gyro-harmonic number found in the studied zebras.