Observations of the resonance radio emission at 245 MHz as an indicator of new regime of electron acceleration and plasma heating A. Struminsky Space Research Institute, Moscow, Russia RHESSI workshop, Annapolis, 2010 August 4
INTRODUCTION • A proportionality of the effective plasma temperature (GOES) to the logarithm of hard X-ray intensity was discovered during pre-flare and impulsive phases of the 2006 December 6 solar flare (Struminsky&Zimovets, 2010) • Red – hard X-ray >150 keV (ACS SPI), black – effective temperature (GOES) • The proportionality disappears after beginning of plasma expansion, when plasma cooling becomes more effective than its heating by non-thermal electrons • Radio emission at 245 MHz is an an indicator of new regime of electron acceleration and plasma heating (blue, out of scale). • Low density 109 cm3 and rapid expansion.
The successive flaringon Sep 13, 2005 (Wang et al., 2007) • The initial flare at19:22UT destabilized nearby loops , leading to the filament eruption with the second flare. • The filament erupted 13 minutes after the initial flare onset showed a slow rising; • After 19:35 UT, thewhole flux loop system was brightened and erupted outward rapidly,most probably due to the complete loss of equilibrium.
Time scale – impulsive, gradual • The temperature profile on 2005 Sep 13 (blue) shows two time scales – impulsive ( ~10 min) and gradual (40 min) • Black – a typical temperature increase associated with filament eruption (2001 Nov 21).
September 13, 2005 (X1.5/2B) • Radio emission at 245 MHz starts close to rapid filament eruption • Radio emission at 15.4 GHz indicates processes of electron acceleration
December 6, 2006 Time profiles are shifted to get a a coincidence of maximums at 245 MHz
CONCLUSIONS • Large solar flares is a consequence of impulsive flares and filament eruptions • Sharp peaks at 245 MHz are most likely the resonance ones and correspond to the electron density in the interaction region 109 cm−3 at heights of 104−105 km. • They are a signature of rapid filament eruption and effective cooling of flare plasma