Oxygen torus and its coincidence with EMIC wave in the deep inner magnetosphere: Van Allen Probe B and Arase observations

M. Nosé; A. Matsuoka; A. Kumamoto; Y. Kasahara; M. Teramoto; S. Kurita; J. Goldstein; L. M. Kistler; S. Singh; A. Gololobov; K. Shiokawa; S. Imajo; S. Oimatsu; K. Yamamoto; Y. Obana; M. Shoji; F. Tsuchiya; I. Shinohara; Y. Miyoshi; W. S. Kurth; C. A. Kletzing; C. W. Smith; R. J. MacDowall; H. Spence; G. D. Reeves

doi:10.1186/s40623-020-01235-w

Back

Oxygen torus and its coincidence with EMIC wave in the deep inner magnetosphere: Van Allen Probe B and Arase observations

Journal article

Open access

Peer reviewed

Oxygen torus and its coincidence with EMIC wave in the deep inner magnetosphere: Van Allen Probe B and Arase observations

M. Nosé, A. Matsuoka, A. Kumamoto, Y. Kasahara, M. Teramoto, S. Kurita, J. Goldstein, L. M. Kistler, S. Singh, A. Gololobov, …

Earth, planets, and space, Vol.72(1), pp.111-111

08/03/2020

DOI: 10.1186/s40623-020-01235-w

PMCID: PMC7410109

PMID: 32831576

Files and links (1)

url

https://doi.org/10.1186/s40623-020-01235-wView

Published (Version of record) Open Access

Abstract

We investigate the longitudinal structure of the oxygen torus in the inner magnetosphere for a specific event found on 12 September 2017, using simultaneous observations from the Van Allen Probe B and Arase satellites. It is found that Probe B observed a clear enhancement in the average plasma mass (M) up to 3–4 amu at L = 3.3–3.6 and magnetic local time (MLT) = 9.0 h. In the afternoon sector at MLT ~ 16.0 h, both Probe B and Arase found no clear enhancements in M. This result suggests that the oxygen torus does not extend over all MLT but is skewed toward the dawn. Since a similar result has been reported for another event of the oxygen torus in a previous study, a crescent-shaped torus or a pinched torus centered around dawn may be a general feature of the O+ density enhancement in the inner magnetosphere. We newly find that an electromagnetic ion cyclotron (EMIC) wave in the H+ band appeared coincidently with the oxygen torus. From the lower cutoff frequency of the EMIC wave, the ion composition of the oxygen torus is estimated to be 80.6% H+, 3.4% He+, and 16.0% O+. According to the linearized dispersion relation for EMIC waves, both He+ and O+ ions inhibit EMIC wave growth and the stabilizing effect is stronger for He+ than O+. Therefore, when the H+ fraction or M is constant, the denser O+ ions are naturally accompanied by the more tenuous He+ ions, resulting in a weaker stabilizing effect (i.e., larger growth rate). From the Probe B observations, we find that the growth rate becomes larger in the oxygen torus than in the adjacent regions in the plasma trough and the plasmasphere.

EMIC wave

Inner magnetosphere

Ion composition

Oxygen torus

ULF wave

Details

Title: Subtitle: Oxygen torus and its coincidence with EMIC wave in the deep inner magnetosphere: Van Allen Probe B and Arase observations
Creators: M. Nosé - Nagoya University
A. Matsuoka - Kyoto University
A. Kumamoto - Tohoku University
Y. Kasahara - Kanazawa University
M. Teramoto - Kyushu Institute of Technology
S. Kurita - Kyoto University
J. Goldstein - The University of Texas at San Antonio
L. M. Kistler - Nagoya University
S. Singh - Geological Survey of India
A. Gololobov - North-Eastern Federal University
K. Shiokawa - Nagoya, Japan
S. Imajo - Nagoya University
S. Oimatsu - Kyoto University
K. Yamamoto - The University of Tokyo
Y. Obana - Osaka Electro-Communication University
M. Shoji - Nagoya University
F. Tsuchiya - Tohoku University
I. Shinohara - Japan Aerospace Exploration Agency
Y. Miyoshi - Nagoya University
W. S. Kurth - University of Iowa
C. A. Kletzing - University of Iowa
C. W. Smith - Durham, NH USA
R. J. MacDowall - Goddard Space Flight Center
H. Spence - University of New Hampshire
G. D. Reeves - Los Alamos National Laboratory
Resource Type: Journal article
Publication Details: Earth, planets, and space, Vol.72(1), pp.111-111
DOI: 10.1186/s40623-020-01235-w
PMID: 32831576
PMCID: PMC7410109
NLM abbreviation: Earth Planets Space
ISSN: 1343-8832
eISSN: 1880-5981
Publisher: Springer Berlin Heidelberg
Grant note: ; NAS5-01072 / ; 16H04057; 17K18804; 17K0566; 16H06286; 15H05815; 15H05747 / ; 20H01959 / ;
Language: English
Date published: 08/03/2020
Academic Unit: Physics and Astronomy
Record Identifier: 9984428829302771

Metrics

13 Record Views

19 Times Cited - Web of Science

See more details