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Longitudinal Extent of Magnetospheric ELF/VLF Waves using Multipoint PWING Ground Stations at Subauroral Latitudes
Author(s) -
Takeshita Yuhei,
Shiokawa Kazuo,
Ozaki Mitsunori,
Manninen Jyrki,
Oyama ShinIchiro,
Connors Martin,
Baishev Dmitry,
Kurkin Vladimir,
Oinats Alexey
Publication year - 2019
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1029/2019ja026810
Subject(s) - electrojet , van allen radiation belt , earth's magnetic field , magnetosphere , geophysics , physics , ionosphere , geomagnetic storm , hiss , plasmasphere , electron precipitation , geomagnetic latitude , particle acceleration , extremely low frequency , electron , magnetic field , quantum mechanics
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.