Journal article
Controlling Factors of Chorus Spectral Gaps
Journal of geophysical research. Space physics, Vol.129(10), e2023JA031893
10/2024
DOI: 10.1029/2023JA031893
Abstract
Abstract The present study compares a single‐band chorus wave against a banded chorus wave observed by Van Allen Probes at adjacent times, and demonstrates that the single‐band chorus wave is associated with an anisotropic electron population over a broad energy range, while the banded chorus wave is accompanied by an electron phase space density plateau and an electron anisotropy reduction around Landau resonant energies. We further compare banded chorus waves with different spectral gap widths, and show that a wider spectral gap is associated with electron isotropization extending to higher energies with respect to the equatorial Landau resonant energy. We suggest that early generated chorus waves isotropize electrons via Landau resonant acceleration, and the waves that propagate to higher latitudes isotropize electrons at higher energies. The isotropization extending to higher energies leads to a larger spectral gap of new chorus waves after electrons bounce back to the equator.
Plain Language Summary Naturally occurring chorus waves in the Earth's magnetosphere typically consist of two frequency bands. The present study aims to explain what controls the bandwidth of the chorus frequency gap that separates chorus waves into two bands. We first compare a single‐band chorus wave against a banded chorus wave observed by a Van Allen Probe satellite at adjacent times. The banded chorus wave is accompanied by an electron phase space density plateau and an electron anisotropy reduction due to Landau resonance, while this phenomenon is not clearly seen in association with the single‐band chorus wave. We further compare banded chorus waves with different gap widths. Satellite observations indicate that a wider frequency gap is associated with electron isotropization extending to higher energies. We suggest that Landau resonant acceleration extending to high latitudes isotropizes electron distribution at high energies, leading to new chorus waves with a large frequency gap. In contrast, Landau resonance that stops at a relatively lower latitude (due to waves being damped) leads to new chorus waves with a smaller frequency gap.
Key Points Freshly injected anisotropic electron population without a PSD plateau generates single band chorus waves Banded chorus waves are more common because electrons usually have already undergone isotropization at Landau resonant energies along the drift path Landau acceleration extending to higher energies occurring at higher latitudes leads to more pronounced electron isotropization and larger chorus spectral gaps
Details
- Title: Subtitle
- Controlling Factors of Chorus Spectral Gaps
- Creators
- Jinxing Li - University of California, Los AngelesJacob Bortnik - University of California, Los AngelesWen Li - Boston UniversityXin An - University of California, Los AngelesLarry R. Lyons - University of California, Los AngelesWilliam S. Kurth - University of IowaGeorge B. Hospodarsky - University of IowaDavid P. Hartley - University of IowaGeoffrey D. Reeves - Los Alamos National LaboratoryHerbert O. Funsten - New Mexico ConsortiumJ. Bernard Blake - The Aerospace CorporationHarlan Spence - University of New HampshireDaniel N. Baker - Laboratory for Atmospheric and Space Physics
- Resource Type
- Journal article
- Publication Details
- Journal of geophysical research. Space physics, Vol.129(10), e2023JA031893
- Publisher
- AMER GEOPHYSICAL UNION
- DOI
- 10.1029/2023JA031893
- ISSN
- 2169-9380
- eISSN
- 2169-9402
- Grant note
- National Science Foundation: AGS-1847818 NSF: 80NSSC20K1506, 80NSSC19K0845, 80NSSC20K0698 NASA: FG-2018-10936 Alfred P. Sloan Research Fellowship: 967399, 921647, NAS5-01072
JL, JB and XA acknowledge the NSF grant AGS-1923126 and NASA grant LWS- 80NSSC20K0201 and 80NSSC21K0522. JL and JB acknowledge the grant DE-SC0010578 and NASA grants 80NSSC18K1227 and NNX14AI18 G. XA and JB acknowledge the NASA Grant 80NSSC20K0917. WL acknowledges the NASA grants 80NSSC20K1506, 80NSSC19K0845, and 80NSSC20K0698, NSF grant AGS-1847818, as well as the Alfred P. Sloan Research Fellowship FG-2018-10936. This work (including support for WK) is supported by RBSP-ECT and EMFISIS funding provided by JHU/APL contract No. 967399 and 921647 under NASA's prime contract No. NAS5-01072.
- Language
- English
- Date published
- 10/2024
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984719802702771
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