University of Oulu

Takeshita, Y., Shiokawa, K., Ozaki, M., Manninen, J., Oyama, S.‐I., Connors, M., et al. ( 2019). Longitudinal extent of magnetospheric ELF/VLF waves using multipoint PWING ground stations at subauroral latitudes. Journal of Geophysical Research: Space Physics, 124, 9881– 9892. https://doi.org/10.1029/2019JA026810

Longitudinal extent of magnetospheric ELF/VLF waves using multipoint PWING ground stations at subauroral latitudes

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Author: Takeshita, Yuhei1; Shiokawa, Kazuo1; Ozaki, Mitsunori2;
Organizations: 1Institute for Space‐Earth Environmental Research, Nagoya University, Nagoya, Japan
2Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa, Japan
3Sodankylä Geophysical Observatory, Finland
4National Institute of Polar Research, Tachikawa, Japan
5Ionospheric Physics Research Unit, University of Oulu, Oulu, Finland
6Athabasca University Observatories, Athabasca University, Athabasca, Alberta, Canada
7Yu.G.Shafer Institute of Cosmophysical Research and Aeronomy of Siberian Branch of the Russian Academy of Sciences, Yakut Scientific Centre of Siberian Branch of the Russian Academy of Sciences, Yakutsk, Russia
8Institute of Solar‐Terrestrial Physics, Siberian Branch of the Russian Academy of Sciences, Irkutsk, Russia
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 6.8 MB)
Persistent link: http://urn.fi/urn:nbn:fi-fe202002064739
Language: English
Published: American Geophysical Union, 2019
Publish Date: 2020-07-24
Description:

Abstract

Magnetospheric extremely low frequency/very low frequency (ELF/VLF) waves are plasma waves emitted from high‐energy electrons in the magnetosphere. These waves have received much attention, as they contribute to the acceleration and loss of relativistic electrons in the radiation belts through wave‐particle interactions. The longitudinal extent of ELF/VLF waves has not been well‐understood, although the extent is important in quantitative evaluation of relativistic electron variations. In this study, we analyzed data from continuous ground‐based simultaneous observations of ELF/VLF waves over a 2‐month period in November and December of 2017, using six loop antennas located at roughly equal intervals around the north geomagnetic pole at ∼60° magnetic latitudes. We estimated the longitudinal extent of magnetospheric ELF/VLF waves based on their occurrence rate. Our results showed that the ELF/VLF wave occurrence rate differed by twofold to threefold, depending on the longitudes of the observation sites. We explain this difference in terms of longitudinal differences in the ionosphere’s magnetic field intensity, possibly due to the electron loss that occurs during the bounce motion at longitudes of small magnetic field intensity. Based on our statistical analysis, we estimated the typical longitudinal extent of ELF/VLF waves as ∼76°. Time series analysis results showed that the large longitudinal extent of the ELF/VLF waves occurs frequently during the main phase of geomagnetic storms and is also associated with substorms represented by the auroral electrojet index.

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Series: Journal of geophysical research. Space physics
ISSN: 2169-9380
ISSN-E: 2169-9402
ISSN-L: 2169-9380
Volume: 124
Issue: 12
Pages: 9881 - 9892
DOI: 10.1029/2019JA026810
OADOI: https://oadoi.org/10.1029/2019JA026810
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Subjects:
Funding: The ELF/VLF data at ATH, GAK, KAP, IST, and MAM used in this paper are available from the Institute for Space‐Earth Environmental Research (ISEE), Nagoya University (https://ergsc.isee.nagoya-u.ac.jp/index.shtml.en). We express our sincere gratitude to Y. Katoh, H. Hamaguchi, Y. Yamamoto, and T. Adachi of ISEE for their continued technical support. The ELF/VLF loop antennas at ATH, GAK, KAP, IST, and MAM are operated with local support provided by Athabasca University, Geophysical Institute of University of Alaska Fairbanks, Virginia Polytechnic Institute and State University, the Institute of Solar‐Terrestrial Physics (ISTP), and the Yu.G. Shafer Institute of Cosmophysical Research and Aeronomy (SHICRA), respectively. The ELF/VLF wave data obtained at KAN are available at the Sodankyla Geophysical Observatory, University of Oulu, Finland (http://www.sgo.fi/Data/VLF/VLF.php). The AE and SYM‐H indices used in this paper were provided by the World Data Center‐C2, Kyoto University and are available at http://wdc.kugi.kyoto_u.ac.jp. We were also supported by the KAKENHI (Grant‐in‐Aid for Scientific Research; 23403009, 25247080, JP 15H05815, JP 16H06286, and JP 17K06456) from the Japan Society for the Promotion of Science, by the Ministry of Science and Higher Education of the Russian Federation and the Siberian Branch of the Russian Academy of Sciences (project II.16.2.1, registration number AAAA‐A17‐117021450059‐3) and were partially funded by the Russian Foundation for Basic Research (18‐45‐140037; D. B.).
Copyright information: © 2019. American Geophysical Union. All Rights Reserved.