Multifrequency compressional magnetic field oscillations and their relation to multiharmonic toroidal mode standing Alfvén waves

Kazue Takahashi; Colin Waters; Karl‐Heinz Glassmeier; Craig A Kletzing; William S Kurth; Charles W Smith

doi:10.1002/2015JA021780

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Multifrequency compressional magnetic field oscillations and their relation to multiharmonic toroidal mode standing Alfvén waves

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Multifrequency compressional magnetic field oscillations and their relation to multiharmonic toroidal mode standing Alfvén waves

Kazue Takahashi, Colin Waters, Karl‐Heinz Glassmeier, Craig A Kletzing, William S Kurth and Charles W Smith

Journal of geophysical research. Space physics, Vol.120(12), pp.10,384-10,403

12/2015

DOI: 10.1002/2015JA021780

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Abstract

The power spectrum of the compressional component of magnetic fields observed by the Van Allen Probes spacecraft near the magnetospheric equator in the dayside plasmasphere sometimes exhibits regularly spaced multiple peaks at frequencies below 50 mHz. We show by detailed analysis of events observed on two separate days in early 2014 that the frequencies change smoothly with the radial distance of the spacecraft and appear at or very near the frequencies of the odd harmonics of mutiharmonic toroidal mode standing Alfvén waves seen in the azimuthal component of the magnetic field. Even though the compressional component had a low amplitude on one of the selected days, its spectral properties are highlighted by computing the ratio of the spectral powers of time series data obtained from two spatially separated Van Allen Probes spacecraft. The spectral similarity of the compressional and azimuthal components suggests that the compressional component contains field line resonance characteristics. Key Points Power spectra of plasmaspheric magnetic field oscillations exhibit multiple peaks The oscillations are driven by disturbances external to the magnetosphere The spectral peaks occur at field line resonance frequencies

compressional oscillations

field line resonance

Pc3‐Pc4 band

plasmasphere

Van Allen Probes

Details

Title: Subtitle: Multifrequency compressional magnetic field oscillations and their relation to multiharmonic toroidal mode standing Alfvén waves
Creators: Kazue Takahashi - Johns Hopkins University Applied Physics Laboratory
Colin Waters - University of Newcastle
Karl‐Heinz Glassmeier - Technische Universität Braunschweig
Craig A Kletzing - University of Iowa
William S Kurth - University of Iowa
Charles W Smith - University of New Hampshire
Resource Type: Journal article
Publication Details: Journal of geophysical research. Space physics, Vol.120(12), pp.10,384-10,403
DOI: 10.1002/2015JA021780
ISSN: 2169-9380
eISSN: 2169-9402
Number of pages: 20
Grant note: NASA (NNX13AE02G; NNX14AB97G) NSF (AGS-1106427)
Language: English
Date published: 12/2015
Academic Unit: Physics and Astronomy
Record Identifier: 9984199850702771

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