@article{5c843c94b61b488a9a3e4fe8388ed9a9,
title = "Impulsively Excited Nightside Ultralow Frequency Waves Simultaneously Observed on and off the Magnetic Equator",
abstract = "The Arase spacecraft is capable of observing ultralow frequency waves in the inner magnetosphere at intermediate magnetic latitudes, a region sparsely covered by previous spacecraft missions. We report a series of impulsively excited fundamental toroidal mode standing Alfv{\'e}n waves in the midnight sector observed by Arase outside the plasmasphere at magnetic latitudes 13–24°. The wave onsets are concurrent with Pi2 onsets detected by the Van Allen Probe B spacecraft at the magnetic equator in the duskside plasmasphere and by ground magnetometers at low latitudes. The duration of each toroidal wave packet is ∼20 min, which is much longer than that of the corresponding Pi2 wave packet. The toroidal waves cannot be the source of high-latitude Pi2 waves because they were not detected on the ground near the magnetic field footprint of Arase. Overall, the toroidal wave event lasted more than 2 hr and allowed us to use the wave frequency to estimate the plasma mass density at L = 6.1–8.3. The mass density (in amu/cm3) is higher than the electron density (cm−3) by a factor of ∼6, which implies that 17–33% of the ions were O+.",
author = "Kazue Takahashi and Denton, {Richard E.} and Tetsuo Motoba and Ayako Matsuoka and Yasumasa Kasaba and Yoshiya Kasahara and Mariko Teramoto and Masafumi Shoji and Naoko Takahashi and Yoshizumi Miyoshi and Masahito Nos{\'e} and Atsushi Kumamoto and Fuminori Tsuchiya and Redmon, {Robert J.} and Rodriguez, {Juan V.}",
note = "Funding Information: K. T. was supported by NASA Grants NNX15AI95G and NNX17AD34G. R. E. D. was supported by NSF Grant AGS-1105790. This study was supported by The Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research on Innovative Areas (Grant 15H05815) and Grant-in-Aid for Scientific Research (Grant 16H04056). Part of this study was carried out under the joint research program of the Institute for Space-Earth Environmental Research (ISEE), Nagoya University. The Arase data were provided by the ERG Science Center operated by the Institute of Space and Astronautical Science, Japan Aerospace and Exploration Agency and ISEE/Nagoya University (https://ergsc.isee.nagoya-u.ac.jp/). The ERG data processors are as follows: MGF L2 v01.00 for the magnetic field, PWE/EFD L2 ver01 (3 March 2018) for the electric field, and PWE/HFA L3 ver00.02 for the electron density. The Arase satellite data will be publicly available via ERG Science Center on a project-agreed schedule. Other data are available from the following sources: Van Allen Probes Science Operations Centers located at University of Iowa (http://emfisis.physics.uiowa.edu) and University of Minnesota (http://www.space.umn.edu/missions/ rbspefw-home-university-of-minnesota), for Van Allen Probes; NOAA National Centers for Environmental Information (http://satdat.ngdc.noaa.gov), for GOES; Leirvogur Magnetic Observatory (http://cygnus.raunvis.hi.is//halo/ lrv.htmland), for the LRV magnetometer; USGS (https://geomag.usgs.gov/ws/edge/), for the HON and SJG magnetometers; and World Data Center for Geomagnetism, Kyoto (http://wdc.kugi.kyoto-u.ac.jp), for the AE and AL indices. W. Kurth is acknowledged for deriving electron density from the spectra of plasma waves detected by Van Allen Probes. Funding Information: K.?T. was supported by NASA Grants NNX15AI95G and NNX17AD34G. R.?E.?D. was supported by NSF Grant AGS-1105790. This study was supported by The Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research on Innovative Areas (Grant 15H05815) and Grant-in-Aid for Scientific Research (Grant 16H04056). Part of this study was carried out under the joint research program of the Institute for Space-Earth Environmental Research (ISEE), Nagoya University. The Arase data were provided by the ERG Science Center operated by the Institute of Space and Astronautical Science, Japan Aerospace and Exploration Agency and ISEE/Nagoya University (https://ergsc.isee.nagoya-u.ac.jp/). The ERG data processors are as follows: MGF L2 v01.00 for the magnetic field, PWE/EFD L2 ver01 (3 March 2018) for the electric field, and PWE/HFA L3 ver00.02 for the electron density. The Arase satellite data will be publicly available via ERG Science Center on a project-agreed schedule. Other data are available from the following sources: Van Allen Probes Science Operations Centers located at University of Iowa (http://emfisis.physics.uiowa.edu) and University of Minnesota (http://www.space.umn.edu/missions/rbspefw-home-university-of-minnesota), for Van Allen Probes; NOAA National Centers for Environmental Information (http://satdat.ngdc.noaa.gov), for GOES; Leirvogur Magnetic Observatory (http://cygnus.raunvis.hi.is//halo/lrv.htmland), for the LRV magnetometer; USGS (https://geomag.usgs.gov/ws/edge/), for the HON and SJG magnetometers; and World Data Center for Geomagnetism, Kyoto (http://wdc.kugi.kyoto-u.ac.jp), for the AE and AL indices. W. Kurth is acknowledged for deriving electron density from the spectra of plasma waves detected by Van Allen Probes. Publisher Copyright: {\textcopyright}2018. American Geophysical Union. All Rights Reserved.",
year = "2018",
month = aug,
day = "28",
doi = "10.1029/2018GL078731",
language = "English",
volume = "45",
pages = "7918--7926",
journal = "Geophysical Research Letters",
issn = "0094-8276",
publisher = "American Geophysical Union",
number = "16",
}