Minute pulsations in microwaves and X-rays during the flare on May 6, 2005

Abstract

Quasi-periodic pulsations are a common feature in the emission associated with solar flares. In particular, pulsations with periods of tens of seconds to a few minutes are often seen in microwave and hard X-ray emission. We examine the spatial and temporal structure of the emission during the flare on May 6, 2005. The source of the flare is a magnetically nonsymmetric arcade with denser magnetic field at the eastern ribbon and more dispersed magnetic field at the western ribbon. The flare visible in microwaves and X-rays covers only a part of the magnetic arcade. The source at 34 GHz shows dynamics independent from the source at 17 GHz during the impulsive and decay phases. The temporal fine structure of the microwave and X-ray emission is studied with correlation, Fourier, and wavelet methods. Damped oscillations with period about 65 s and mean amplitude 3% are found during the decay phase of the flare. Joint analysis of the temporal fine structure and the spatial structure of the pulsations allows us to associate the oscillations with the global slow magnetoacoustic mode. We analyse the flare within the MHD approach. And we briefly discuss an alternative mechanisms.