Why we are interesting in study in faint solar flares?

L. Kashapova, D. Zhdanov, S. Lesovoi, A. Kudryavtseva (ISTP SB RAS, Irkutsk, Russia) and Lomonosov BDRG collaboration( The Skobeltsyn Institute, MSU, Moscow, Russia)

Institute of Solar Terrestrial Physics SB RAS, Irkutsk, Russia

Studying the solar flares we are usually facing with that the powerful events are combination of phenomena and processes of different nature. This results to different explanations based on different scenarios which sometimes contradict to each other. The faint solar flares ( the B, C GOES classes and lower) are attractive objects for study of the processes of energy release and transport . They mostly present В«pure casesВ» and provide more clear data for revealing of the mechanisms and testing of the theoretical models and hypothesis. However the low level of their emission both in X-rays and microwaves is obstacle for the progress in this field. New generation of radio telescopes and combination of X-ray data (time profiles and spectral data) with observations in radio (microwaves) and results of modeling allow to diagnose the energy release processes with confidence even for very weak events. Nowadays we have the multiple scenario set for weak solar flare from the high temperature events to "cold flares". We present the possibilities of such diagnostics by the example of the several events and discuss limits of such approach basing on the modern observational data.

Non-stationary properties of quasi-periodic pulsations in flare emission

Elena Kupriyanova1, Dmitrii Kolotkov2, Anastasiya Kudryavtseva3, Larisa Kashapova3

1 Central Astronomical Observatory at Pulkovo of RAS, Saint Petersburg, Russia

2 CFSA, University of Warwick, Coventry, UK

3 Institute of Solar-Terrestrial Physics SB RAS, Irkutsk, Russia

Abstract

One of the principal questions in solar physics is related to the energy release and energy transport in solar flares. Quasi-periodic pulsations (QPPs) are an intrinsic property of the flares. They are observed in various frequency ranges of electromagnetic spectrum, from gamma rays to radio waves, during all phases of solar flares. Development of diagnostics of mechanisms of the QPPs allows for understanding the processes both qualitatively and quantitatively. Current methods of diagnostics of QPPs are developed based on the QPPs having either stationary or slowly varying parameters. However, non-stationarity of the parameters (deviation from a sine curve) of the QPPs is predicted from theoretical models of QPPs based on either on MHD oscillations of plasma structures or on auto-oscillations or on a combination of the previous two. Recently, the evidences were found on the presence of the QPPs with the time dependent parameters (hereinafter, non-stationary QPPs) in solar and stellar flares. Here we present first results of analysis of three solar flares aiming to distinguish between natural non-stationarity associated with a time-dependent physical process and the one appeared due to a multi-modal structure of QPPs. First time, data of the renewed Siberian Radioheliograph (SRH) at 4–8 GHz are applied for this reason.