V. M. Fridman

Manifestation of pulsation instability in solar radio emission preceding proton flares

The investigation of solar radio emission fluctuations at the wavelength λ ∼- 3 cm led to the discovery of a visible increase in pulsations with periods of about 30–120 min prior to proton flares. These pulsations were observed before all (seven) proton flares included in our cycle of observations from 1969 to 1974. The phenomenon was not found to occur before non-proton flares. The assumption is made that the observed pulsations are a manifestation of pre-flare instability in coronal structures. Estimations have been made for fluctuations of the gyro-resonance radiation from the regions above spots associated with the magnetic field variations when a groove instability of a coronal condensation is developed. They are in good agreement with the observational data. The discovered manifestation of the pre-flare instability in fluctuations of the solar radio emission open new ways to study the flare development and to predict geo-effective phenomena on the Sun.

The Results of Studying Nonstationary Processes on the Sun by Radioastronomical Methods

This paper presents the results of studies of solar phenomena performed at the Radiophysical Research Institute (NIRFI) in the last years and based on the data of measuring the solar microwave radiation. We obtained new results concerning fragmentation of the regions of initial energy release during solar flares, their spatial and temporal dynamics, the physical conditions in flaring loops, the dynamics of energetic particles accelerated during flares, and the characteristics of sporadic radio emission during the formation and propagation of coronal mass ejections in the lower layers of the solar atmosphere.

A study of preflare situations using spectral data on fluxes of solar radio emission in the period from 1970 to 1994

We present the results of observations performed at “Zimenki” facility at six radio frequencies over a broad spectral interval in the period that covers more than two 11-year cycles of the solar activity. In the analysis we have determined the laws of the spectral-time development of the preflare situations for the proton and non-proton events, which differ by the duration and range of spectral composition of the phenomena. The phenomenon of the “directivity” of precursor radiation is studied depending on the location of sources on the solar disc.

Spectral Features in Solar Microwave Emission Preceeding CME Onset

The sporadic solar radio emission of patrol solar radio observations within the periods 1980, 1984–1989 and of observations with high temporal and spectral resolution in 1989 are used to find the manifestation of pre CMEs activity. To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Quasi-Periodic Components of Solar Microwave Emission Preceeding The CME Onset on 19 October, 2001

The results of solar microwave observations in the Radio Astronomical Observatory NIRFI “Zimenki” are examined. Data analysis shows the presence of periodic component, that arose prior to burst connected to CMEs onset, and its absence after burst. Obtained data are compared with the dynamics of the development of activity on the solar disk. Results can be considered as the illustration of the dynamics of wave motions in the periods of flare activity.