Radio Time Profiles and Magnetic Configurations of Two 2-step Triggering Solar Flares

Observational data of two radio events(2001/04/10 and 2001/10/19) associated with the fast time structures obtained with the spectrometers(0.65~7.6 GHz) at the National Astronomical Observatories,Chinese Academy of Sciences(Beijing and Yunnan)(NAOC) and NoRH/17GHz as well as TRACE/EUV(171Å) and Yohkoh/SXT are analyzed in this paper.The time profiles and observational characteristics of two radio events are similar.By comparison with the observational images of coronal magnetic polarities for these two events,it is found that the complex radio bursts are caused by the evolution of the active regions including multiply magnetic polarities and finally results in the decimetric radio bursts(secondary triggering) around the top of the post-flare loops.In particular,it is indicated that two decimetric radio bursts are attributed to the behavior of post-flare loops.The 2-step triggering flares(corresponding to the broadband microwave and narrowband decimetric bursts) are corresponding to the bipolar magnetic configuration,respectively.This manifests that these two bursts are produced by the similar flare models.It is presumed that the 2-step triggering drivers of the flares are the magnetic flux emergence or cancellation(there are magnetic unipole or bipoles of new appearance or disappearance during the evolution of magnetic structures),while their triggers are the magnetic reconnection of bipole inverted 'Y-type' configuration.It is thought that the emission mechanisms about the broad-band microwave and the narrowband decimetric radio bursts could be attributed to the gyro-synchrotron emission and the plasma emission processes,respectively.