Multifrequency compressional magnetic field oscillations and their relation to multiharmonic toroidal mode standing Alfvén waves. Issue 12 (14th December 2015)

• Record Type: Journal Article
• Authors: Takahashi, Kazue; Waters, Colin; Glassmeier, Karl‐Heinz; Kletzing, Craig A.; Kurth, William S.; Smith, Charles W.
• Is Part Of: Journal of geophysical research. Volume 120:Issue 12(2015:Dec.)
• Page Start: 10, 384
• Page End: 10, 403
• Publication Date: 2015-12-14
• Subjects: compressional oscillations -- Pc3‐Pc4 band -- plasmasphere -- field line resonance -- Van Allen Probes; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1002/2015JA021780
• Languages: English
• ISSNs: 2169-9380

Abstract

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