[IGPP Everyone] TOMORROW: Space Physics Seminar, Friday Feb. 13th: Electron Energy Partition in the Above-the-Looptop Solar Hard X-ray Sources (M. Oka, UCB SSL)
Emmanuel V. Masongsong
emasongsong at igpp.ucla.edu
Thu Feb 12 15:43:32 PST 2015
Dr. Oka is available for meetings tomorrow, Friday, from 10-12. Grad students and researchers are encouraged to attend lunch with our guest, please RSVP and meet at Slichter 2712 11:50am tomorrow.
SPACE PHYSICS SEMINAR
DEPARTMENT OF EARTH, PLANETARY, AND SPACE SCIENCES
DEPARTMENT OF ATMOSPHERIC AND OCEANIC SCIENCES
UNIVERSITY OF CALIFORNIA, LOS ANGELES
(EPSS M288A, AOS M275A )
Mitsuo Oka
UC Berkeley SSL
Electron Energy Partition in the Above-the-Looptop Solar Hard X-ray Sources
Abstract:
Solar flares produce non-thermal electrons with energies up to tens of MeVs. To understand the origin of energetic electrons, coronal hard X-ray (HXR) sources in particular 'above-the-looptop' sources have been studied extensively. However, it still remains unclear how energies are partitioned between thermal and non-thermal electrons within the above-the-looptop source. Here we show that the kappa distribution, when compared to conventional spectral models, can better characterize the above-the-looptop HXRs (>~15 keV) observed in four different cases. Based on the kappa distribution model, we found that the 2012 July 19 flare showed the largest non-thermal fraction of electron energies about 50%, suggesting equipartition of energies. Considering results of particle-in-cell (PIC) simulations as well as density estimates of the four cases studied, we propose a scenario in which electron acceleration is achieved primarily by collisionless magnetic reconnection but the electron energy partition in the above-the-looptop source depends on the source density.
Friday, February 13th, 2015
Room 6704 Geology
3:30 - 5:00 PM
Refreshments served after the seminar in Room 6850.
In-Charge
V. Angelopoulos
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