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Title: Excitation of O + Band EMIC Waves Through H + Ring Velocity Distributions: Van Allen Probe Observations

Abstract

A typical case of electromagnetic ion cyclotron (EMIC) emissions with both He + band and O + band waves was observed by Van Allen Probe A on 14 July 2014. These emissions occurred in the morning sector on the equator inside the plasmasphere, in which region O + band EMIC waves prefer to appear. Through property analysis of these emissions, it is found that the He + band EMIC waves are linearly polarized and propagating quasi–parallelly along the background magnetic field, while the O + band ones are of linear and left–hand polarization and propagating obliquely with respect to the background magnetic field. Using the in situ observations of plasma environment and particle data, excitation of these O + band EMIC waves has been investigated with the linear growth theory. The calculated linear growth rate shows that these O + band EMIC waves can be locally excited by ring current protons with ring velocity distributions. The comparison of the observed wave spectral intensity and the calculated growth rate suggests that the density of H + rings providing the free energy for the instability has decreased after the wave grows. Furthermore, this paper provides a direct observational evidence to the excitationmore » mechanism of O + band EMIC waves: ring current protons with ring distributions provide the free energy supporting the instability in the presence of rich O + in the plasmasphere.« less

Authors:
ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1];  [1];  [2]; ORCiD logo [3]; ORCiD logo [4]
  1. Wuhan Univ., Wuhan (China)
  2. GFZ German Research Center for Geosciences, Potsdam (Germany)
  3. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  4. Univ. of Minnesota, Minneapolis, MN (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
National Aeronautic and Space Administration (NASA); USDOE
OSTI Identifier:
1542833
Report Number(s):
LA-UR-18-26636
Journal ID: ISSN 0094-8276
Grant/Contract Number:  
89233218CNA000001
Resource Type:
Accepted Manuscript
Journal Name:
Geophysical Research Letters
Additional Journal Information:
Journal Volume: 45; Journal Issue: 3; Journal ID: ISSN 0094-8276
Publisher:
American Geophysical Union
Country of Publication:
United States
Language:
English
Subject:
O+ band EMIC waves; ring distributions; linear wave growth

Citation Formats

Yu, Xiongdong, Yuan, Zhigang, Huang, Shiyong, Yao, Fei, Wang, Dedong, Funsten, Herbert O., and Wygant, John R. Excitation of O+ Band EMIC Waves Through H+ Ring Velocity Distributions: Van Allen Probe Observations. United States: N. p., 2018. Web. doi:10.1002/2018GL077109.
Yu, Xiongdong, Yuan, Zhigang, Huang, Shiyong, Yao, Fei, Wang, Dedong, Funsten, Herbert O., & Wygant, John R. Excitation of O+ Band EMIC Waves Through H+ Ring Velocity Distributions: Van Allen Probe Observations. United States. doi:10.1002/2018GL077109.
Yu, Xiongdong, Yuan, Zhigang, Huang, Shiyong, Yao, Fei, Wang, Dedong, Funsten, Herbert O., and Wygant, John R. Fri . "Excitation of O+ Band EMIC Waves Through H+ Ring Velocity Distributions: Van Allen Probe Observations". United States. doi:10.1002/2018GL077109. https://www.osti.gov/servlets/purl/1542833.
@article{osti_1542833,
title = {Excitation of O+ Band EMIC Waves Through H+ Ring Velocity Distributions: Van Allen Probe Observations},
author = {Yu, Xiongdong and Yuan, Zhigang and Huang, Shiyong and Yao, Fei and Wang, Dedong and Funsten, Herbert O. and Wygant, John R.},
abstractNote = {A typical case of electromagnetic ion cyclotron (EMIC) emissions with both He+ band and O+ band waves was observed by Van Allen Probe A on 14 July 2014. These emissions occurred in the morning sector on the equator inside the plasmasphere, in which region O+ band EMIC waves prefer to appear. Through property analysis of these emissions, it is found that the He+ band EMIC waves are linearly polarized and propagating quasi–parallelly along the background magnetic field, while the O+ band ones are of linear and left–hand polarization and propagating obliquely with respect to the background magnetic field. Using the in situ observations of plasma environment and particle data, excitation of these O+ band EMIC waves has been investigated with the linear growth theory. The calculated linear growth rate shows that these O+ band EMIC waves can be locally excited by ring current protons with ring velocity distributions. The comparison of the observed wave spectral intensity and the calculated growth rate suggests that the density of H+ rings providing the free energy for the instability has decreased after the wave grows. Furthermore, this paper provides a direct observational evidence to the excitation mechanism of O+ band EMIC waves: ring current protons with ring distributions provide the free energy supporting the instability in the presence of rich O+ in the plasmasphere.},
doi = {10.1002/2018GL077109},
journal = {Geophysical Research Letters},
number = 3,
volume = 45,
place = {United States},
year = {2018},
month = {2}
}

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