Generation of lower and upper bands of electrostatic electron cyclotron harmonic waves in the Van Allen radiation belts

Journal Article · Mon May 22 00:00:00 EDT 2017 · Geophysical Research Letters

DOI:https://doi.org/10.1002/2017GL073051· OSTI ID:1402656

Zhou, Qinghua  ^[1]; Xiao, Fuliang  ^[1]; Yang, Chang  ^[1]; Liu, Si  ^[1]; He, Yihua  ^[1]; Baker, D. N.  ^[2]; Spence, H. E.  ^[3]; Reeves, Geoffrey D.  ^[4]; Funsten, Herbert O.  ^[4]

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1. Changsha Univ. of Science and Technology, Changsha (China)
2. Univ. of Colorado, Boulder, CO (United States)
3. Univ. of New Hampshire, Durham, NH (United States)
4. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

Electrostatic electron cyclotron harmonic (ECH) waves generated by the electron loss cone distribution can produce efficient scattering loss of plasma sheet electrons, which has a significant effect on the dynamics in the outer magnetosphere. Here we report two ECH emission events around the same location L≈ 5.7–5.8, MLT ≈ 12 from Van Allen Probes on 11 February (event A) and 9 January 2014 (event B), respectively. The spectrum of ECH waves was centered at the lower half of the harmonic bands during event A, but the upper half during event B. The observed electron phase space density in both events is fitted by the subtracted bi-Maxwellian distribution, and the fitting functions are used to evaluate the local growth rates of ECH waves based on a linear theory for homogeneous plasmas. ECH waves are excited by the loss cone instability of 50 eV–1 keV electrons in the lower half of harmonic bands in the low-density plasmasphere in event A, and 1–10 keV electrons in the upper half of harmonic bands in a relatively high-density region in event B. Here, the current results successfully explain observations and provide a first direct evidence on how ECH waves are generated in the lower and upper half of harmonic frequency bands.

• Research Organization: Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: National Aeronautics and Space Administration (NASA); USDOE
• Grant/Contract Number: AC52-06NA25396
• OSTI ID: 1402656
• Report Number(s): LA-UR-17-28037; TRN: US1702891
• Journal Information: Geophysical Research Letters, Vol. 44, Issue 11; ISSN 0094-8276
• Publisher: American Geophysical Union
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
Heliospheric and Magnetospheric Physics
ECH waves
wave-particle interaction
RBSP results