Radio observations of the quasiperiodic oscillations of plasma structures in the solar atmosphere and their physical nature

G Gelfreikh

Radio observations of the oscillations of different types of the radio sources observed at the microwave maps of the sun are presented. The observations were carried out using modern large antennas, such as RATAN-600, radio heliographs Badary (SSRT) and Nobeyama, RT-22 (Crimea).. Both time variation of brightness (in total intensity and polarization) and position were analyzed. Most of the plasma structures of the solar atmosphere show the presence of quasiperiodic processes. Methods of the wavelet analysis were used.to study nonstationary nature of the oscillations.

Above sunspots with strong magnetic field dominate the oscillations with periods around 3 minutes. However, the shorter periods (below one minute) also present, periods of tens and even hundreds minutes above the error level are often significant. In most other features of active regions oscillations periods around ten minutes are typical. Longer periods of about 50 and 80 minutes seem to be regular. Some of them clearly have nonstationary nature. Well known from optical observations 5 minute oscillations are often registered but not as a regular process. The dynamic variation of oscillations were found in connection with development of flare activity of an active region. The oscillations of the magnetic field at the top of coronal loops were studied analyzing the position of inversion of polarization in QT region.

Possible resonance processes in the solar atmosphere which are responsible for the periodicity of radio oscillations are discussed. They include resonator in side and outside of the regions of generation of the investigated radio emission. Global oscillations may also be responsible for some types of the radio periodic processes.

The results above have been obtained by several working groups and was supported by some grants including INTAS 00543, RFBR 02-02-16548 and 03-02-17357, OFN-16.