Title: Whistler anisotropy instabilities as the source of banded chorus: Van Allen Probes observations and particle-in-cell simulations

Abstract

Magnetospheric banded chorus is enhanced whistler waves with frequencies ω_r < Ω_e, where Ω_e is the electron cyclotron frequency, and a characteristic spectral gap at ω_r ≃ Ω_e/2. This paper uses spacecraft observations and two-dimensional particle-in-cell simulations in a magnetized, homogeneous, collisionless plasma to test the hypothesis that banded chorus is due to local linear growth of two branches of the whistler anisotropy instability excited by two distinct, anisotropic electron components of significantly different temperatures. The electron densities and temperatures are derived from Helium, Oxygen, Proton, and Electron instrument measurements on the Van Allen Probes A satellite during a banded chorus event on 1 November 2012. The observations are consistent with a three-component electron model consisting of a cold (a few tens of eV) population, a warm (a few hundred eV) anisotropic population, and a hot (a few keV) anisotropic population. The simulations use plasma and field parameters as measured from the satellite during this event except for two numbers: the anisotropies of the warm and the hot electron components are enhanced over the measured values in order to obtain relatively rapid instability growth. The simulations show that the warm component drives the quasi-electrostatic upper band chorus and that themore » hot component drives the electromagnetic lower band chorus; the gap at ~Ω_e/2 is a natural consequence of the growth of two whistler modes with different properties.« less

Authors:

Fu, Xiangrong ^[1]; Cowee, Misa M. ^[1]; Friedel, Reinhard H. ^[1]; Funsten, Herbert O. ^[1]; Gary, S. Peter ^[2]; Hospodarsky, George B. ^[3]; Kletzing, Craig ^[3]; Kurth, William ^[3]; Larsen, Brian A. ^[1]; Liu, Kaijun ^[4]; MacDonald, Elizabeth A. ^[5]; Min, Kyungguk ^[4]; Reeves, Geoffrey D. ^[1]; Skoug, Ruth M. ^[1]; Winske, Dan ^[1]

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+ Show Author Affiliations

1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2. Space Science Institute, Boulder, CO (United States)
3. Univ. of Iowa, Iowa City, IA (United States). Dept. of Physics and Astronomy.
4. Auburn Univ., Auburn, AL (United States). Dept. of Physics.
5. NASA/Goddard Space Flight Center, Greenbelt, MD (United States)

Publication Date:

Wed Oct 22 00:00:00 EDT 2014

Research Org.:

Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)

Sponsoring Org.:

USDOE

OSTI Identifier:

1212455

Grant/Contract Number:  

AC52-06NA25396

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Geophysical Research. Space Physics

Additional Journal Information:

Journal Volume: 119; Journal Issue: 10; Journal ID: ISSN 2169-9380

Publisher:

American Geophysical Union

Country of Publication:

United States

Language:

English

Subject:

58 GEOSCIENCES