Solar flares are the most powerful natural processes in the solar system, and hence are subject to extensive studies. The main practical interest in solar flares relates to their influence (via hard electromagnetic emission, energetic charged particles, and coronal mass ejections) on environments of the inner solar system planets and interplanetary space. This is related to the rapidly developing field of space weather and the issues of stability and safety of various space-borne and ground-based technologies. Moreover, solar flares provide a unique possibility for the study of basic physical processes in plasmas, such as charged-particle acceleration and magnetic energy conversion. This knowledge is fundamental for various astrophysical and geophysical plasma systems, and relevant to the controlled-fusion efforts. Also, the use of the similarities and differences of solar flares and flares observed on other sun-like stars allows one to assess the habitable conditions on exoplanets. Recent discovery of the giant flares (superflares) on the sun-like stars with the Kepler and ground-based telescopes poses a question of whether the Sun can produce such a superflare, and with which probability.
Virtually all solar (and probably also stellar) flares are accompanied by sequences of intermittent bursts (pulses) of X-ray and radio emissions with characteristic durations from several sub-seconds up to dozens of minutes. This observational fact indicates clearly that processes of energy release and acceleration of charged particles in flares are essentially non-stationary. One intriguing peculiarity of these highly non-stationary processes is that sometimes they operate in a quasi-periodic regime but sometimes are not. It is still a riddle as to why some flares display quasi-periodic pulsations (QPPs) of electromagnetic emission, whereas others seemed to produce randomly distributed bursts. Undoubtedly, each reliable model of solar flares must be able to explain this feature. Moreover, the apparent similarity of QPPs detected in solar flares and superflares may indicate the similarity of the physical mechanisms operating in them.
Several theoretical mechanisms have been proposed to explain pulsatory regimes of energy release in flares. Among them are mechanisms based on: a) various types of MHD oscillations in magnetoplasma structures of the solar corona; b) bursty regimes of magnetic reconnection; c) cyclic self-organizing regimes of plasma instabilities; d) "magnetic domino effect"; etc. To choose a correct class of models one need to combine detailed, state-of-the-art, spatially-resolved observations in different wave-bands and comprehensive forward modeling. This approach can make progress in solving the problem of flare pulsations and the problem of flare energy release in general.
Our Team will focus on comprehensive analysis of solar flare space- and ground-based observations and advanced modeling to deepen current knowledge about non-stationary processes of flare energy release manifested as pulsations of flare electromagnetic emission. The Team is composed of international experts in the relevant areas of solar physics and is aiming to:
- develop more rigorous criteria of quasi-periodicity for solar flare light curves;
- utilize new methods of analysis of nonlinear and non-stationary datasets;
- develop an advanced classification of different types of pulsations in solar flares;
- perform detailed multi-wavelength spatially-resolved analysis of the sources of pulsations in the large sample of solar flares using modern observational datasets (RHESSI, Fermi, SDO, IRIS, Lomonosov, Vernov, Spectr-R, NoRH/NoRP, SSRT, etc.);
- assess adequacy and improve the existent flare models;
- evaluate the possible role of pulsations in solar-terrestrial connections;
- develop a strategy of exploration of pulsations in solar and stellar flares with space- and ground-based instruments in the coming years.