Speaker: Jeongwoo Lee
1. School of Space Research, Kyung Hee University, Yongin 17104, Korea
2. Space Weather Research Laboratory, New Jersey Institute of Technology, Newark, NJ 07102, U.S.A

Time: 2:30pm June 29

Location: 1514 conference room

Abstract: A composite (or compound) flare has a characteristic time profile consisting of both an impulsive flare and a gradual (or long-duration) flare. There can be various ways to view this phenomenon: for instance, either a magnetically confined flare preceding an eruptive flare or a nonthermal flare followed by a thermal flare. For the former interpretation, analysis of magnetic field structure will be needed, and, for the latter, separation of thermal/nonthermal components in radiations will. In this talk, I will discuss these issues based on our recent studies on a composite event consisting of an impulsive flare SOL2015-06-21T01:42 (GOES class M2.0) and a long-duration flare SOL2015-06-21T02:36 (M2.6) from NOAA Active Region 12371. We used the microwave maps from the Nobeyama Radioheliograph (NoRH) to infer high-energy electrons, and the EUV and magnetogram data from the Solar Dynamics Observatory (SDO) for the magnetic field context. A nonlinear force-free field extrapolation was also performed to assist the analysis of the magnetic field structure. Our studies have revealed that a composite flare possesses much more complicated characteristics than the above speculation solely based on the time profile, and that it offers a special opportunity for clarifying how a flux rope evolves to be able to break out of a magnetically confined system.