Series of high-frequency slowly drifting structures mapping the flare magnetic field reconnection

Abstract

Rare series of the slowly drifting structures observed during two solar flares (April 11, 2001 and March 18, 2003) in the 0.8-4.5 GHz frequency range are studied. Their time-frequency evolution is compared with topological and X-ray characteristics of the flares. Based on recent modelling of the magnetic field reconnection in the bursting and intermittent regime, it is proposed that these slowly drifting structures map the flare magnetic field reconnection. In such a scenario the drifting structures correspond to the radio emission from primary and secondary plasmoids which are formed in the extended current sheet due to tearing and coalescence processes and they move upwards in the solar atmosphere. An increase and decrease of the frequency drifts of the drifting structures in the initial and decaying flare phases are interpreted as an increase and decrease of the reconnection rate, respectively. On the other hand, individual bursts in the drifting pulsating structures are considered to be radio manifestations of separate electron beams accelerated during the secondary tearing processes. The observed characteristic times are compared with those theoretically predicted and the basic plasma parameters in the flare process are estimated.