Unraveling the excitation mechanisms of highly oblique lower band chorus waves
Abstract
Excitation mechanisms of highly oblique, quasi‐electrostatic lower band chorus waves are investigated using Van Allen Probes observations near the equator of the Earth's magnetosphere. Linear growth rates are evaluated based on in situ, measured electron velocity distributions and plasma conditions and compared with simultaneously observed wave frequency spectra and wave normal angles. Accordingly, two distinct excitation mechanisms of highly oblique lower band chorus have been clearly identified for the first time. The first mechanism relies on cyclotron resonance with electrons possessing both a realistic temperature anisotropy at keV energies and a plateau at 100–500 eV in the parallel velocity distribution. The second mechanism corresponds to Landau resonance with a 100–500 eV beam. In both cases, a small low‐energy beam‐like component is necessary for suppressing an otherwise dominating Landau damping. Our new findings suggest that small variations in the electron distribution could have important impacts on energetic electron dynamics.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Sep 03, 2016
- Source ID
- 10.1002/2016gl070386
Entities
People
- Anton V. Artemyev
- Craig Kletzing
- D. Mourenas
- Geoffrey D Reeves
- George G. Hospodarsky
- H. O. Funsten
- Harlan Spence
- J. Bortnik
- R. M. Thorne
- Wen Li
- William S. Kurth
Organizations
- Air Force Office of Scientific Research
- Boston University
- Los Alamos National Laboratory
- National Aeronautics and Space Administration
- University of California, Los Angeles
- University of Iowa
- University of New Hampshire