Subpacket structures in EMIC rising tone emissions observed by the THEMIS probes

Satoko Nakamura; Yoshiharu Omura; Masafumi Shoji; M. Nosé; Danny Summers; Vassilis Angelopoulos

doi:10.1002/2014ja020764

journal article Sep 01, 2015

Subpacket structures in EMIC rising tone emissions observed by the THEMIS probes

Satoko Nakamura Yoshiharu Omura Masafumi Shoji M. Nosé

Danny Summers Vassilis Angelopoulos

Journal of Geophysical Research: Space Physics Vol. 120 No. 9 pp. 7318-7330 · Wiley

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Abstract

AbstractWe report subpacket structures found in electromagnetic ion cyclotron (EMIC) rising tone emissions observed by the Time History of Events and Macroscale Interactions during Substorms (THEMIS) probes. We investigate three typical cases in detail. The first case shows a continuous single rising tone with four obvious subpackets, and the second case is characterized by a patchy emission with multiple subpackets triggered in a broadband frequency. The third case looks like a smooth rising tone without any obvious subpacket in the fast Fourier transform spectrum, while its amplitude contains small peaks with increasing frequencies. The degree of polarization of each subpacket is generally higher than 0.8 with a left‐handed polarization, and the wave direction of the subpackets is typically field aligned. We show that the time evolution of the observed frequency and amplitude can be reproduced consistently by nonlinear growth theory. We also compare the observed time span of each subpacket structure with the theoretical trapping time for second‐order cyclotron resonance. They are consistent, indicating that an individual subpacket is generated through a nonlinear wave growth process which excites an element in accordance with the theoretically predicted optimum amplitude.

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Metrics

40

Citations

33

References

Details

Published: Sep 01, 2015
Vol/Issue: 120(9)
Pages: 7318-7330
License: View

Authors

S

Satoko Nakamura

Graduate School of Science Kyoto University Kyoto Japan

Y

Yoshiharu Omura

Research Institute for Sustainable Humanosphere Kyoto University Kyoto Japan

M

Masafumi Shoji

Solar‐Terrestrial Environment Laboratory Nagoya Japan

M

M. Nosé

Graduate School of Science Kyoto University Kyoto Japan

D

Danny Summers

Research Institute for Sustainable Humanosphere Kyoto University Kyoto Japan; Department of Mathematics and Statistics Memorial University of Newfoundland St. John's Newfoundland Canada

V

Vassilis Angelopoulos

Department of Earth, Planetary and Space Sciences and Institute of Geophysics and Planetary Physics University of California Los Angeles California USA

Funding

Japan Society for the Promotion of Science Award: 26287120

Natural Sciences and Engineering Research Council of Canada

Cite This Article

Satoko Nakamura, Yoshiharu Omura, Masafumi Shoji, et al. (2015). Subpacket structures in EMIC rising tone emissions observed by the THEMIS probes. Journal of Geophysical Research: Space Physics, 120(9), 7318-7330. https://doi.org/10.1002/2014ja020764

Subpacket structures in EMIC rising tone emissions observed by the THEMIS probes

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