Investigation of Quasi-periodic Variations in Hard X-rays of Solar Flares |
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| Authors: | J Jakimiec M Tomczak |
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| Institution: | 1.Astronomical Institute,University of Wroc?aw,Wroc?aw,Poland |
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| Abstract: | The aim of the present paper is to use quasi-periodic oscillations in hard X-rays (HXRs) of solar flares as a diagnostic tool
for the investigation of impulsive electron acceleration. We have selected a number of flares which showed quasi-periodic
oscillations in hard X-rays and their loop-top sources could be easily recognized in HXR images. We have considered MHD standing
waves to explain the observed HXR oscillations. We interpret these HXR oscillations as being due to oscillations of magnetic
traps within cusp-like magnetic structures. This is confirmed by the good correlation between periods of the oscillations
and the sizes of the loop-top sources. We argue that a model of oscillating magnetic traps is adequate to explain the observations.
During the compressions of a trap, particles are accelerated, but during its expansions plasma, coming from chromospheric
evaporation, fills the trap, which explains the large number of electrons being accelerated during a sequence of strong pulses.
The advantage of our model of oscillating magnetic traps is that it can explain both the pulses of electron acceleration and
quasi-periodicity of their distribution in time. |
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