Polarization of magnetospheric ULF waves excited by an interplanetary shock on 27 February 2014
Abstract
Many previous studies have reported that magnetospheric ultralow frequency waves excited by interplanetary shocks exhibit a strong toroidal component, corresponding to azimuthal displacement of magnetic field lines. However, the toroidal oscillations excited by an interplanetary shock on 27 February 2014 and observed on the dayside by multiple spacecraft were accompanied by a strong poloidal component (radial field line displacement). The frequency of the toroidal oscillations changed with the radial distance of the spacecraft as expected for standing Alfvén waves. We run a 3-D linear numerical simulation of this wave event using a model magnetosphere with a realistic radial variation of the Alfvén velocity. The simulated wave fields, when sampled at a radial distance comparable to those of the observations in the real magnetosphere, exhibit polarization similar to the observations. In the simulation, the poloidal component comes from radially standing fast mode waves and the toroidal component results from a field line resonance driven by the fast mode waves. As a consequence, the relative amplitude and phase of the toroidal and poloidal components change with radial distance.
Citation
Takahashi , K , Elsden , T , Wright , A N & Degeling , A 2023 , ' Polarization of magnetospheric ULF waves excited by an interplanetary shock on 27 February 2014 ' , Journal of Geophysical Research: Space Physics . https://doi.org/10.1029/2023JA031608
Publication
Journal of Geophysical Research: Space Physics
Status
Peer reviewed
ISSN
2169-9402Type
Journal article
Description
Funding: KT was supported by NASA Grants NNX17AD34G, 80NSSC19K0259, and 80NSSC21K0453. TE was partially funded by Leverhulme Early Career Fellowship ECF-2019-155. ANW was partially funded by the Science and Technology Facilities Council (STFC) Grant (ST/N000609/1). AWD was supported by NSFC Grants 42225405 and NAF\R1\19“1047”.Collections
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