Multiwavelength Stereoscopic Observation of the May 1, 2013 Solar Flare and CME
Abstract
A M-class behind-the-limb solar flare on 1 May 2013 (SOL2013-05-01T02:32), accompanied by a ( 400 km/s) CME was observed by several space-based observatories with different viewing angles. We investigated the RHESSI-observed occulted hard X-ray emissions that originated at least 0.1 above the flare site. Emissions below 10 keV revealed a hot, extended (11 MK, >60 arcsec) thermal source from the escaping CME core, with densities around 109 cm-3. In such a tenuous hot plasma, ionization times scales are several minutes, consistent with the non-detection of the hot CME core in SDO/AIA's 131 filter. The non-thermal RHESSI source originated from an even larger area (100 arcsec) at lower densities (108 cm-3) located above the hot core, but still behind the CME front. This indicates that the observed part of the non-thermal electrons are not responsible for heating the CME core. Possibly the hot core was heated by non-thermal electrons before it became visible from Earth, meaning that the un-occulted part of the non-thermal emission likely originates from a more tenuous part of the CME core, where non-thermal electrons survive long enough to became visible from Earth. Simultaneous hard X-ray spectra from the Mars Odyssey mission, which viewed the flare on disk, indicated that the number of non-thermal electrons >20 keV within the high coronal source is 0.1 - 0.5\% compared to the number within the chromospheric flare ribbons. The detection of high coronal hard X-ray sources in this moderate size event suggests that such sources are likely a common feature within solar eruptive events.