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 Alfvén waves in the mi...
Saved in:
| Main Authors: | , , , , , , , , , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Wiley
2018-08-01
|
| Series: | Geophysical Research Letters |
| Online Access: | https://doi.org/10.1029/2018GL078731 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| _version_ | 1850075348368097280 |
|---|---|
| author | Kazue Takahashi Richard E. Denton Tetsuo Motoba Ayako Matsuoka Yasumasa Kasaba Yoshiya Kasahara Mariko Teramoto Masafumi Shoji Naoko Takahashi Yoshizumi Miyoshi Masahito Nosé Atsushi Kumamoto Fuminori Tsuchiya Robert J. Redmon Juan V. Rodriguez |
| author_facet | Kazue Takahashi Richard E. Denton Tetsuo Motoba Ayako Matsuoka Yasumasa Kasaba Yoshiya Kasahara Mariko Teramoto Masafumi Shoji Naoko Takahashi Yoshizumi Miyoshi Masahito Nosé Atsushi Kumamoto Fuminori Tsuchiya Robert J. Redmon Juan V. Rodriguez |
| author_sort | Kazue Takahashi |
| collection | DOAJ |
| description | 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 Alfvén 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+. |
| format | Article |
| id | doaj-art-040313442ed74f8f9a057caf329e09e4 |
| institution | DOAJ |
| issn | 0094-8276 1944-8007 |
| language | English |
| publishDate | 2018-08-01 |
| publisher | Wiley |
| record_format | Article |
| series | Geophysical Research Letters |
| spelling | doaj-art-040313442ed74f8f9a057caf329e09e42025-08-20T02:46:20ZengWileyGeophysical Research Letters0094-82761944-80072018-08-0145167918792610.1029/2018GL078731Impulsively Excited Nightside Ultralow Frequency Waves Simultaneously Observed on and off the Magnetic EquatorKazue Takahashi0Richard E. Denton1Tetsuo Motoba2Ayako Matsuoka3Yasumasa Kasaba4Yoshiya Kasahara5Mariko Teramoto6Masafumi Shoji7Naoko Takahashi8Yoshizumi Miyoshi9Masahito Nosé10Atsushi Kumamoto11Fuminori Tsuchiya12Robert J. Redmon13Juan V. Rodriguez14The Johns Hopkins University Applied Physics Laboratory Laurel MD USADepartment of Physics and Astronomy Dartmouth College Hanover NH USAThe Johns Hopkins University Applied Physics Laboratory Laurel MD USAInstitute of Space and Astronautical Science Sagamihara JapanDepartment of Geophysics Tohoku University Sendai JapanGraduate School of Natural Science and Technology Kanazawa University Kanazawa JapanInstitute of Space‐Earth Environmental Research Nagoya University Nagoya JapanInstitute of Space‐Earth Environmental Research Nagoya University Nagoya JapanGraduate School of Science, Department of Earth and Planetary Science The University of Tokyo Tokyo JapanInstitute of Space‐Earth Environmental Research Nagoya University Nagoya JapanGraduate School of Science Kyoto University Kyoto JapanDepartment of Geophysics Tohoku University Sendai JapanDepartment of Geophysics Tohoku University Sendai JapanNational Centers for Environmental Information National Oceanic and Atmospheric Administration Boulder CO USANational Centers for Environmental Information National Oceanic and Atmospheric Administration Boulder CO USAAbstract 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 Alfvén 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+.https://doi.org/10.1029/2018GL078731 |
| spellingShingle | Kazue Takahashi Richard E. Denton Tetsuo Motoba Ayako Matsuoka Yasumasa Kasaba Yoshiya Kasahara Mariko Teramoto Masafumi Shoji Naoko Takahashi Yoshizumi Miyoshi Masahito Nosé Atsushi Kumamoto Fuminori Tsuchiya Robert J. Redmon Juan V. Rodriguez Impulsively Excited Nightside Ultralow Frequency Waves Simultaneously Observed on and off the Magnetic Equator Geophysical Research Letters |
| title | Impulsively Excited Nightside Ultralow Frequency Waves Simultaneously Observed on and off the Magnetic Equator |
| title_full | Impulsively Excited Nightside Ultralow Frequency Waves Simultaneously Observed on and off the Magnetic Equator |
| title_fullStr | Impulsively Excited Nightside Ultralow Frequency Waves Simultaneously Observed on and off the Magnetic Equator |
| title_full_unstemmed | Impulsively Excited Nightside Ultralow Frequency Waves Simultaneously Observed on and off the Magnetic Equator |
| title_short | Impulsively Excited Nightside Ultralow Frequency Waves Simultaneously Observed on and off the Magnetic Equator |
| title_sort | impulsively excited nightside ultralow frequency waves simultaneously observed on and off the magnetic equator |
| url | https://doi.org/10.1029/2018GL078731 |
| work_keys_str_mv | AT kazuetakahashi impulsivelyexcitednightsideultralowfrequencywavessimultaneouslyobservedonandoffthemagneticequator AT richardedenton impulsivelyexcitednightsideultralowfrequencywavessimultaneouslyobservedonandoffthemagneticequator AT tetsuomotoba impulsivelyexcitednightsideultralowfrequencywavessimultaneouslyobservedonandoffthemagneticequator AT ayakomatsuoka impulsivelyexcitednightsideultralowfrequencywavessimultaneouslyobservedonandoffthemagneticequator AT yasumasakasaba impulsivelyexcitednightsideultralowfrequencywavessimultaneouslyobservedonandoffthemagneticequator AT yoshiyakasahara impulsivelyexcitednightsideultralowfrequencywavessimultaneouslyobservedonandoffthemagneticequator AT marikoteramoto impulsivelyexcitednightsideultralowfrequencywavessimultaneouslyobservedonandoffthemagneticequator AT masafumishoji impulsivelyexcitednightsideultralowfrequencywavessimultaneouslyobservedonandoffthemagneticequator AT naokotakahashi impulsivelyexcitednightsideultralowfrequencywavessimultaneouslyobservedonandoffthemagneticequator AT yoshizumimiyoshi impulsivelyexcitednightsideultralowfrequencywavessimultaneouslyobservedonandoffthemagneticequator AT masahitonose impulsivelyexcitednightsideultralowfrequencywavessimultaneouslyobservedonandoffthemagneticequator AT atsushikumamoto impulsivelyexcitednightsideultralowfrequencywavessimultaneouslyobservedonandoffthemagneticequator AT fuminoritsuchiya impulsivelyexcitednightsideultralowfrequencywavessimultaneouslyobservedonandoffthemagneticequator AT robertjredmon impulsivelyexcitednightsideultralowfrequencywavessimultaneouslyobservedonandoffthemagneticequator AT juanvrodriguez impulsivelyexcitednightsideultralowfrequencywavessimultaneouslyobservedonandoffthemagneticequator |