Investigation of Small-Scale Electron Density Irregularities Observed by the Arase and Van Allen Probes Satellites Inside and Outside the Plasmasphere

Neethal Thomas; Kazuo Shiokawa; Yoshizumi Miyoshi; Yoshiya Kasahara; Iku Shinohara; Atsushi Kumamoto; Fuminori Tsuchiya; Ayako Matsuoka; Satoshi Kasahara; Shoichiro Yokota; Kunihiro Keika; Tomoaki Hori; Kazushi Asamura; Shiang Yu Wang; Yoichi Kazama; Sunny Wing Yee Tam; Tzu Fang Chang; Bo Jhou Wang; John Wygant; Aaron W Breneman; Geoffrey Reeves

doi:10.1029/2020JA027917

Investigation of Small-Scale Electron Density Irregularities Observed by the Arase and Van Allen Probes Satellites Inside and Outside the Plasmasphere

Neethal Thomas, Kazuo Shiokawa, Yoshizumi Miyoshi, Yoshiya Kasahara, Iku Shinohara, Atsushi Kumamoto, Fuminori Tsuchiya, Ayako Matsuoka, Satoshi Kasahara, Shoichiro Yokota, Kunihiro Keika, Tomoaki Hori, Kazushi Asamura, Shiang Yu Wang, Yoichi Kazama, Sunny Wing Yee Tam, Tzu Fang Chang, Bo Jhou Wang, John Wygant, Aaron W BrenemanGeoffrey Reeves

Physics and Astronomy (Twin Cities)

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10 Scopus citations

Abstract

In situ electron density profiles obtained from Arase in the night magnetic local time (MLT) sector and from RBSP-B covering all MLTs are used to study the small-scale density irregularities present in the plasmasphere and near the plasmapause. Electron density perturbations with amplitudes >10% from background density and with time-scales less than 30-min are investigated here as the small-scale density irregularities. The statistical survey of the density irregularities is carried out using nearly 2 years of density data obtained from RBSP-B and 4 months of data from Arase satellites. The results show that density irregularities are present globally at all MLT sectors and L-shells both inside and outside the plasmapause, with a higher occurrence at L > 4. The occurrence of density irregularities is found to be higher during disturbed geomagnetic and interplanetary conditions. The case studies presented here revealed: (1) The plasmaspheric density irregularities observed during both quiet and disturbed conditions are found to coexist with the hot plasma sheet population. (2) During quiet periods, the plasma waves in the whistler-mode frequency range are found to be modulated by the small-scale density irregularities, with density depletions coinciding well with the decrease in whistler intensity. Our observations suggest that different source mechanisms are responsible for the generation of density structures at different MLTs and geomagnetic conditions.

Original language	English (US)
Article number	e2020JA027917
Journal	Journal of Geophysical Research: Space Physics
Volume	126
Issue number	3
DOIs	https://doi.org/10.1029/2020JA027917
State	Published - Mar 2021

Bibliographical note

Funding Information:
The authors would like to thank NASA’s Van Allen Probe team for the use of EFW LEVEL 3 data product obtained from ( http://www.space.umn.edu/rbspefw-data/ ), EMFISIS data from ( https://emfisis.physics.uiowa.edu/data/index ), the plasma data of HOPE and MagEIS instruments from ( https://rbsp-ect.newmexicoconsortium.org/science/DataDirectories.php ) and the plasma data of RBSPICE instrument from ( http://rbspice.ftecs.com/Data.html ). The geomagnetic and solar wind indices used in the study are downloaded from NASA’s OMNI data base in Coordinated Data Analysis web ( https://cdaweb.gsfc.nasa.gov/index.html/ ). This work is supported by JSPS KAKENHI (15H05815, 16H06286, 15H05747, 17H00728, and 20H01959).

Funding Information:
Science data of the ERG (Arase) satellite were obtained from the ERG Science Center operated by ISAS/JAXA and ISEE/Nagoya University (http://ergsc.isee.nagoya-u.ac.jp/, Miyoshi et?al.,?2018a). The Arase satellite data is publicly available via ERG Science Center. The present study analyzed Level-2 omni-directional flux data of LEP-e v01.01, LEP-i v03.00, MEP-e v01.02, MEP-i v01.03, and orbit Level-2 v02 and PWE/HFA Level-3 v01.02 data. Arase satellite data sets for this research are available in these in-text data citation references: Wang et?al.?(2018), Asamura et?al.?(2018b), S. Kasahara et?al.?(2018a), Yokota et?al.?(2018), and Miyoshi et?al.?(2018b).

Publisher Copyright:
© 2021. The Authors.

Keywords

Arase
Van Allen Probes
electron density
inner magnetosphere
plasmasphere
small-scale density irregularities

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Thomas, N., Shiokawa, K., Miyoshi, Y., Kasahara, Y., Shinohara, I., Kumamoto, A., Tsuchiya, F., Matsuoka, A., Kasahara, S., Yokota, S., Keika, K., Hori, T., Asamura, K., Wang, S. Y., Kazama, Y., Tam, S. W. Y., Chang, T. F., Wang, B. J., Wygant, J., ... Reeves, G. (2021). Investigation of Small-Scale Electron Density Irregularities Observed by the Arase and Van Allen Probes Satellites Inside and Outside the Plasmasphere. Journal of Geophysical Research: Space Physics, 126(3), Article e2020JA027917. https://doi.org/10.1029/2020JA027917

Investigation of Small-Scale Electron Density Irregularities Observed by the Arase and Van Allen Probes Satellites Inside and Outside the Plasmasphere. / Thomas, Neethal; Shiokawa, Kazuo; Miyoshi, Yoshizumi et al.
In: Journal of Geophysical Research: Space Physics, Vol. 126, No. 3, e2020JA027917, 03.2021.

Research output: Contribution to journal › Article › peer-review

Thomas, N, Shiokawa, K, Miyoshi, Y, Kasahara, Y, Shinohara, I, Kumamoto, A, Tsuchiya, F, Matsuoka, A, Kasahara, S, Yokota, S, Keika, K, Hori, T, Asamura, K, Wang, SY, Kazama, Y, Tam, SWY, Chang, TF, Wang, BJ, Wygant, J, Breneman, AW & Reeves, G 2021, 'Investigation of Small-Scale Electron Density Irregularities Observed by the Arase and Van Allen Probes Satellites Inside and Outside the Plasmasphere', Journal of Geophysical Research: Space Physics, vol. 126, no. 3, e2020JA027917. https://doi.org/10.1029/2020JA027917

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title = "Investigation of Small-Scale Electron Density Irregularities Observed by the Arase and Van Allen Probes Satellites Inside and Outside the Plasmasphere",

abstract = "In situ electron density profiles obtained from Arase in the night magnetic local time (MLT) sector and from RBSP-B covering all MLTs are used to study the small-scale density irregularities present in the plasmasphere and near the plasmapause. Electron density perturbations with amplitudes >10% from background density and with time-scales less than 30-min are investigated here as the small-scale density irregularities. The statistical survey of the density irregularities is carried out using nearly 2 years of density data obtained from RBSP-B and 4 months of data from Arase satellites. The results show that density irregularities are present globally at all MLT sectors and L-shells both inside and outside the plasmapause, with a higher occurrence at L > 4. The occurrence of density irregularities is found to be higher during disturbed geomagnetic and interplanetary conditions. The case studies presented here revealed: (1) The plasmaspheric density irregularities observed during both quiet and disturbed conditions are found to coexist with the hot plasma sheet population. (2) During quiet periods, the plasma waves in the whistler-mode frequency range are found to be modulated by the small-scale density irregularities, with density depletions coinciding well with the decrease in whistler intensity. Our observations suggest that different source mechanisms are responsible for the generation of density structures at different MLTs and geomagnetic conditions.",

keywords = "Arase, Van Allen Probes, electron density, inner magnetosphere, plasmasphere, small-scale density irregularities",

author = "Neethal Thomas and Kazuo Shiokawa and Yoshizumi Miyoshi and Yoshiya Kasahara and Iku Shinohara and Atsushi Kumamoto and Fuminori Tsuchiya and Ayako Matsuoka and Satoshi Kasahara and Shoichiro Yokota and Kunihiro Keika and Tomoaki Hori and Kazushi Asamura and Wang, {Shiang Yu} and Yoichi Kazama and Tam, {Sunny Wing Yee} and Chang, {Tzu Fang} and Wang, {Bo Jhou} and John Wygant and Breneman, {Aaron W} and Geoffrey Reeves",

note = "Funding Information: The authors would like to thank NASA{\textquoteright}s Van Allen Probe team for the use of EFW LEVEL 3 data product obtained from ( http://www.space.umn.edu/rbspefw-data/ ), EMFISIS data from ( https://emfisis.physics.uiowa.edu/data/index ), the plasma data of HOPE and MagEIS instruments from ( https://rbsp-ect.newmexicoconsortium.org/science/DataDirectories.php ) and the plasma data of RBSPICE instrument from ( http://rbspice.ftecs.com/Data.html ). The geomagnetic and solar wind indices used in the study are downloaded from NASA{\textquoteright}s OMNI data base in Coordinated Data Analysis web ( https://cdaweb.gsfc.nasa.gov/index.html/ ). This work is supported by JSPS KAKENHI (15H05815, 16H06286, 15H05747, 17H00728, and 20H01959). Funding Information: Science data of the ERG (Arase) satellite were obtained from the ERG Science Center operated by ISAS/JAXA and ISEE/Nagoya University (http://ergsc.isee.nagoya-u.ac.jp/, Miyoshi et?al.,?2018a). The Arase satellite data is publicly available via ERG Science Center. The present study analyzed Level-2 omni-directional flux data of LEP-e v01.01, LEP-i v03.00, MEP-e v01.02, MEP-i v01.03, and orbit Level-2 v02 and PWE/HFA Level-3 v01.02 data. Arase satellite data sets for this research are available in these in-text data citation references: Wang et?al.?(2018), Asamura et?al.?(2018b), S. Kasahara et?al.?(2018a), Yokota et?al.?(2018), and Miyoshi et?al.?(2018b). Publisher Copyright: {\textcopyright} 2021. The Authors.",

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doi = "10.1029/2020JA027917",

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T1 - Investigation of Small-Scale Electron Density Irregularities Observed by the Arase and Van Allen Probes Satellites Inside and Outside the Plasmasphere

AU - Thomas, Neethal

AU - Shiokawa, Kazuo

AU - Miyoshi, Yoshizumi

AU - Kasahara, Yoshiya

AU - Shinohara, Iku

AU - Kumamoto, Atsushi

AU - Tsuchiya, Fuminori

AU - Matsuoka, Ayako

AU - Kasahara, Satoshi

AU - Yokota, Shoichiro

AU - Keika, Kunihiro

AU - Hori, Tomoaki

AU - Asamura, Kazushi

AU - Wang, Shiang Yu

AU - Kazama, Yoichi

AU - Tam, Sunny Wing Yee

AU - Chang, Tzu Fang

AU - Wang, Bo Jhou

AU - Wygant, John

AU - Breneman, Aaron W

AU - Reeves, Geoffrey

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PY - 2021/3

Y1 - 2021/3

N2 - In situ electron density profiles obtained from Arase in the night magnetic local time (MLT) sector and from RBSP-B covering all MLTs are used to study the small-scale density irregularities present in the plasmasphere and near the plasmapause. Electron density perturbations with amplitudes >10% from background density and with time-scales less than 30-min are investigated here as the small-scale density irregularities. The statistical survey of the density irregularities is carried out using nearly 2 years of density data obtained from RBSP-B and 4 months of data from Arase satellites. The results show that density irregularities are present globally at all MLT sectors and L-shells both inside and outside the plasmapause, with a higher occurrence at L > 4. The occurrence of density irregularities is found to be higher during disturbed geomagnetic and interplanetary conditions. The case studies presented here revealed: (1) The plasmaspheric density irregularities observed during both quiet and disturbed conditions are found to coexist with the hot plasma sheet population. (2) During quiet periods, the plasma waves in the whistler-mode frequency range are found to be modulated by the small-scale density irregularities, with density depletions coinciding well with the decrease in whistler intensity. Our observations suggest that different source mechanisms are responsible for the generation of density structures at different MLTs and geomagnetic conditions.

AB - In situ electron density profiles obtained from Arase in the night magnetic local time (MLT) sector and from RBSP-B covering all MLTs are used to study the small-scale density irregularities present in the plasmasphere and near the plasmapause. Electron density perturbations with amplitudes >10% from background density and with time-scales less than 30-min are investigated here as the small-scale density irregularities. The statistical survey of the density irregularities is carried out using nearly 2 years of density data obtained from RBSP-B and 4 months of data from Arase satellites. The results show that density irregularities are present globally at all MLT sectors and L-shells both inside and outside the plasmapause, with a higher occurrence at L > 4. The occurrence of density irregularities is found to be higher during disturbed geomagnetic and interplanetary conditions. The case studies presented here revealed: (1) The plasmaspheric density irregularities observed during both quiet and disturbed conditions are found to coexist with the hot plasma sheet population. (2) During quiet periods, the plasma waves in the whistler-mode frequency range are found to be modulated by the small-scale density irregularities, with density depletions coinciding well with the decrease in whistler intensity. Our observations suggest that different source mechanisms are responsible for the generation of density structures at different MLTs and geomagnetic conditions.

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Investigation of Small-Scale Electron Density Irregularities Observed by the Arase and Van Allen Probes Satellites Inside and Outside the Plasmasphere

Abstract

Bibliographical note

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