[IGPP Everyone] Reminder - SPACE PHYSICS SEMINAR - Fall Quarter - Friday November 20, 2020 - 3:30pm - UCLA Zoom

[Marjorie Sowmendran]

R E M I N D E R 



SPACE PHYSICS SEMINAR 



ZOOM LINK PROVIDED BELOW 





https://ucla.zoom.us/j/93382900867?pwd=TlVQRmZyVEJFa0FCZWlRMU0yREtjUT09 







Date/Time: November 20, 2020/ 03:30 PM Pacific Time (US and Canada) 




SPACE PHYSICS SEMINAR 




DEPARTMENT OF EARTH, PLANETARY, AND SPACE SCIENCES 

DEPARTMENT OF ATMOSPHERIC AND OCEANIC SCIENCES 

UNIVERSITY OF CALIFORNIA, LOS ANGELES 




Seth Claudepierre 

AOS, UCLA 

The Aerospace Corporation 







Electron Loss Timescales in the Earth’s Radiation Belts: Observations and Theory 



Seth Claudepierre 1,2 , Qianli Ma 3,1 , Jacob Bortnik 1 , Paul O’Brien 2 , Joseph Fennell 2 , and Bern Blake 2 

1 UCLA 

2 The Aerospace Corporation 

3 Boston University 



Energetic and relativistic electrons in the Earth’s radiation belt region are often observed to decay exponentially, suggestive of pitch-angle diffusion in the lowest eigenmode of the diffusion operator. This pitch-angle scattering represents a significant loss process for radiation belt electrons, particularly during quiet times, where the particles are ultimately “precipitated” into the Earth’s upper atmosphere. We use measurements from the MagEIS instrument on NASA’s Van Allen Probes to study these losses and calculate the decay time constants over a wide range of energies (30 keV – 4 MeV) and L values (L = 1.3-6.5) in the inner magnetosphere. Using an automated routine to identify decay intervals, we build a large database of events, from which we compute the average decay times for near-equatorially-mirroring electrons as a function of energy and L. We find long electron lifetimes (~100 days) in the inner zone over a wide range of energies, contrasted with very short, energy-dependent lifetimes (<10 days) in the slot region, in good quantitative agreement with prior empirical estimates. The general structure of the observed lifetime profiles as a function of energy and L is demonstrated to be consistent with quasilinear pitch-angle diffusion by various scattering mechanisms, in particular plasmaspheric hiss. The results also reveal a local minimum in lifetimes in the inner zone at lower energy (<100 keV), attributed to enhanced scattering via ground-based VLF transmitters, which produces a bifurcated (2-belt) inner zone morphology. A reduction in lifetimes is noted at higher energy (>1 MeV) and L, attributed to enhanced EMIC wave scattering. Moreover, we find significant quantitative disagreement at L<3, where the theoretical lifetimes are typically a factor of ~10 larger than the observed, pointing to an additional loss process that is missing from current models. We discuss potential factors that could contribute to this disagreement. 






Friday, November 20, 2020 

3:30 - 5:00 PM 




In-Charge: Marco Velli 














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