Slow Magnetoacoustic Oscillations in the Microwave Emission of Solar Flares

Analysis of the microwave data, obtained in the 17 GHz channel of the Nobeyama Radioheliograph during the M1.6 flare on 4th Nov 2010, revealed the presence of 11.8-min oscillations of the emitting plasma density. The oscilla- tions decayed with the characteristic time of about 25-min. These oscillations are also well-seen in the variation of EUV emission intensity measured in the 335 A channel of SDO/AIA. The observed properties of the oscillations are consistent with the properties of so-called SUMER oscillations, observed in the EUV and soft X-ray bands usually as a periodic Doppler shift. The accepted interpretation of SUMER oscillations is a standing slow magnetoacoustic wave. Our analysis presents the first direct observation of the slow magnetoacoustic oscillations in the microwave emission of a solar flare.
Comment: 12 pages, 4 figures