Observations Directly Linking Relativistic Electron Microbursts to Whistler Mode Chorus: Van Allen Probes and FIREBIRD II

A. W. Breneman, A. Crew, J. Sample, D. Klumpar, A. Johnson, O. Agapitov, M. Shumko, D. L. Turner, O. Santolik, J. R. Wygant, C. A. Cattell, S. Thaller, B. Blake, H. Spence, C. A. Kletzing

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Abstract

We present observations that provide the strongest evidence yet that discrete whistler mode chorus packets cause relativistic electron microbursts. On 20 January 2016 near 1944 UT the low Earth orbiting CubeSat Focused Investigations of Relativistic Electron Bursts: Intensity, Range, and Dynamics (FIREBIRD II) observed energetic microbursts (near L = 5.6 and MLT = 10.5) from its lower limit of 220 keV, to 1 MeV. In the outer radiation belt and magnetically conjugate, Van Allen Probe A observed rising-tone, lower band chorus waves with durations and cadences similar to the microbursts. No other waves were observed. This is the first time that chorus and microbursts have been simultaneously observed with a separation smaller than a chorus packet. A majority of the microbursts do not have the energy dispersion expected for trapped electrons bouncing between mirror points. This confirms that the electrons are rapidly (nonlinearly) scattered into the loss cone by a coherent interaction with the large amplitude (up to ∼900 pT) chorus. Comparison of observed time-averaged microburst flux and estimated total electron drift shell content at L = 5.6 indicate that microbursts may represent a significant source of energetic electron loss in the outer radiation belt.

Original languageEnglish (US)
Pages (from-to)11,265-11,272
JournalGeophysical Research Letters
Volume44
Issue number22
DOIs
StatePublished - Nov 28 2017

Bibliographical note

Funding Information:
The FIREBIRD II data are available at http://solar.physics.montana.edu/ FIREBIRD_II/. This material is based upon work supported by the National Science Foundation under grants 0838034 and 1339414 to Montana State University and under grants 1339534 and 1035642 to the University of New Hampshire. The OMNI data were obtained from the GSFC/SPDF OMNIWeb interface at https://omniweb.gsfc.nasa.gov. Work at the University of Minnesota was supported by a contract from APL, under NASA prime contract NAS5-01072 and NNX12AB23G. O. S. acknowledges support from the GACR17-07027S grant, LTAUSA17070 grant, and from the Praemium Academiae award. Parts of this work was supported by JHU/APL contract 921647 under NASA Prime contract NAS5-01072, JHU/APL contract 131802 under NASA prime contract NNN06AA01C, and JHU/APL contract 922613 (RBSP-EFW). The work of O. A. was supported by the NASA grant NNX16AF85G.

Publisher Copyright:
©2017. The Authors.

Keywords

  • FIREBIRD
  • Van Allen Probe
  • chorus
  • conjunction
  • microburst

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