Zhang, S;
Tian, A;
Shi, Q;
Li, H;
Degeling, AW;
Jonathan Rae, I;
Forsyth, C;
... Pu, Z; + view all
(2018)
Statistical study of ULF waves in the magnetotail by THEMIS observations.
Annales Geophysicae
, 36
(5)
pp. 1335-1346.
10.5194/angeo-36-1335-2018.
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Abstract
Ultra-low-frequency (ULF) waves are ubiquitous in the magnetosphere. Previous studies mostly focused on ULF waves in the dayside or near-Earth region (with radial distance R<12RE). In this study, using the data of the Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission during the period from 2008 to 2015, the Pc5-6 ULF waves in the tail region with X∗-GSM<0, 8RE<R<32RE (mostly on the stretched magnetic field lines) are studied statistically. A total of 1089 azimuthal oscillating events and 566 radial oscillating events were found. The statistical results show that both the azimuthal and radial oscillating events in the magnetotail region (12RE<R<32RE) are more frequently observed in the post-midnight region. The frequency decreases with increasing radial distance from Earth for both azimuthal oscillating events (8RE<R<16RE) and radial oscillating events (8RE<R<14RE), which is consistent with the field line resonances theory. About 52% of events (including the azimuthal and radial oscillating events) are standing waves in the region of 8-16RE, while only 2% are standing waves in the region of 16-32RE. There is no obvious dawn-dusk asymmetry of ULF wave frequency for events in 8RE<R<32RE, which contrasts with the obvious dawn-dusk asymmetry found by previous studies in the inner magnetosphere (4RE<R<9RE). An examination for possible statistical relationships between the ULF wave parameters and substorm occurrences is carried out. We find that the wave frequency is higher after the substorm onset than before it, and the frequency differences are more obvious in the midnight region than in the flank region.
| Type: | Article |
|---|---|
| Title: | Statistical study of ULF waves in the magnetotail by THEMIS observations |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.5194/angeo-36-1335-2018 |
| Publisher version: | https://doi.org/10.5194/angeo-36-1335-2018 |
| Language: | English |
| Additional information: | This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/ |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10059544 |
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