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 excitation mechanism of O⁺ band EMIC waves: ring currentmore » protons with ring distributions provide the free energy supporting the instability in the presence of rich O⁺ in the plasmasphere.« less

Authors:

Yu, Xiongdong  ^[1];

• Search DOE PAGES for author "Yu, Xiongdong"
• Search DOE PAGES for ORCID "0000-0002-1179-1667"

Yuan, Zhigang  ^[1];

• Search DOE PAGES for author "Yuan, Zhigang"
• Search DOE PAGES for ORCID "0000-0002-3756-3507"

Huang, Shiyong  ^[1];

• Search DOE PAGES for author "Huang, Shiyong"
• Search DOE PAGES for ORCID "0000-0002-3595-2525"

Yao, Fei ^[1]; Wang, Dedong ^[2]; Funsten, Herbert O.  ^[3];

• Search DOE PAGES for author "Funsten, Herbert O."
• Search DOE PAGES for ORCID "0000-0002-6817-1039"

Wygant, John R.  ^[4]

• Search DOE PAGES for author "Wygant, John R."
• Search DOE PAGES for ORCID "0000-0002-0564-0440"

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+ Show Author Affiliations

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:

Fri Feb 02 00:00:00 EST 2018

Research Org.:

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

Sponsoring Org.:

National Aeronautics 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:

79 ASTRONOMY AND ASTROPHYSICS; O+ band EMIC waves; ring distributions; linear wave growth