Magnetic Structure and Nonthermal Electrons in the X6.9 Flare on 2011 August 09
Tuesday, 16 December 2014
The 2011 August 09 Flare is one of the largest X-ray flares of Sunspot Cycle 24, but the spatial information is rather limited due to its position close to the western limb. This paper presents the information on the location of high energy electrons derived from the hard X-ray and microwave spectra obtained with the Reuven Ramaty High-Energy Solar Spectroscopic Imager(RHESSI) and the Korean Solar Radio Burst Locator (KSRBL), respectively. The KSRBL microwave spectrum shows significant fluxes at low frequencies, implying that the high energy electrons reside in a coronal volume highly concentrated at strong magnetic fields, and rapidly expanding with decreasing magnetic fields. After a simple modeling of the microwave spectrum, we found that the microwave source should be located above the inner pair of magnetic poles in a large quadrupolar configuration. The time-dependent evolution of magnetic field distribution and total nonthermal energy derived from the microwave spectra is also consistent with the standard picture of multiple magnetic reconnections recurring at a magnetic null point that forms above the magnetic quadrupoles and moves up with time.