SM14C-07
Quantifying Energy-Time Dispersion of Relativistic Electron Microbursts to Constrain Their Generation Mechanism: Coordinated Studies Using FIREBIRD, Van Allen Probes, and BARREL
Monday, 14 December 2015: 17:12
2018 (Moscone West)
Harlan E. Spence, University of New Hampshire Main Campus, Space Science Center, Durham, NH, United States, J. Bernard Blake, Aerospace Corporation Los Angeles, Los Angeles, CA, United States, Alexander B Crew, Organization Not Listed, Washington, DC, United States, J. F. Fennell, Aerospace Corporation, Los Angeles, CA, United States, David M Klumpar, Montana State University, Bozeman, MT, United States, Brian Larsen, The New Mexico Consortium, Los Alamos, NM, United States, Robyn M Millan, Dartmouth College, Hanover, NH, United States, Yoshizumi Miyoshi, Nagoya University, Nagoya, Japan, Thomas Paul O'Brien III, Aerospace Corporation Chantilly, Chantilly, VA, United States, Geoffrey D Reeves, Los Alamos National Laboratory, Los Alamos, NM, United States and Sonya S Smith, University of New Hampshire Main Campus, Durham, NH, United States
Abstract:
In this paper, we quantify properties of relativistic electron precipitation at low altitudes in order to constrain the mechanism(s) for microburst loss occurring in Earth’s radiation belt. Though studied for decades, the physical mechanism(s) responsible for the loss of radiation belt particles through microburst precipitation to the atmosphere remains uncertain, and, unquantified in a global sense. Accordingly, we appeal to new measurements from the NSF FIREBIRD (Focused Investigation of Relativistic Electron Burst Intensity Range and Dynamics) mission. FIREBIRD comprises two 1.5U CubeSats launched in early 2015 into identical coplanar polar low altitude orbits; a small spring imparted a slow separation between the two spacecraft upon orbit insertion. Over the course of the mission, the orbits of the two identically-instrumented spacecraft slowly evolve, sampling spatial scales of electron precipitation measured simultaneously at separations of 10’s to 1000’s of kilometers. FIREBIRD provides electron energy spectra from ~250 keV to > 1MeV, with both high spectral resolution (6 to 12 energy channels) and high temporal resolution (principally operated at ~18 millisecond sampling). To do so, FIREBIRD employs two solid-state detectors on each CubeSat, one an uncollimated detector with a large geometric factor (optimized for weak events) and the other a collimated detector (optimized for intense events). While the primary goal of FIREBIRD is to establish the spatial/temporal coherence of microburst precipitation, it also provides the capability of quantifying on each spacecraft the dispersive properties of microbursts. In this work, we report on the energy-time dispersive qualities of individual bursts, which in turn provide a means for testing models and constraining where and how the bursts are generated. To test these models, we use measurements made near the magnetic equator by the Van Allen Probes mission during times when the two FIREBIRD and two Van Allen Probes spacecraft were in optimal magnetic conjunctions. To the greatest extent possible, we will study times when the four spacecraft were also overflying the August 2015 BARREL (Balloon Array for RBSP Relativistic Electron Losses) campaign to further constrain the temporal and spatial properties of microbursts.
