[IGPP Everyone] 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]

Dr. Oka is available for meetings on Friday from 9-12, and 1-3pm. Grad students and researchers are encouraged to attend lunch with our guest, please RSVP and meet at Slichter 2712 11:50am on Friday. 



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 


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.igpp.ucla.edu/pipermail/everyone/attachments/20150209/a7286d1d/attachment-0001.html>