Bibliography



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Found 2 entries in the Bibliography.


Showing entries from 1 through 2


2021

On the estimation of the ratio of ULF wave electric fields in space and the magnetic fields at the ground.

Abstract Three new methods for estimating a ratio of the ultra-low frequency (ULF; 1–100 mHz) wave equatorial electric field amplitude in the Earth’s magnetosphere to ground magnetic field amplitudes for field line resonances are described. These methods use ratios of the time series extrema, ratios of the envelope waveform and the ratio of the spectral amplitude at the field line resonance frequency. These methods were applied to four ULF resonance intervals; three detected by the Van Allen Probe A spacecraft and one detected by the POLAR spacecraft. The intervals were conjoined with the CARISMA and IMAGE ground magnetometer arrays. The spectral ratio results for the Van Allen Probe intervals were approximately twice to three times the ratios estimated from the two time series based methods. The POLAR interval showed similar values across all three methods. The differences are attributed to broad-band frequency signals that modify the time series amplitudes, while the spectral method avoids these off-resonant frequencies. Based on the results of this study, a spectral based method for calculating the ratio at the field line resonance frequency is best.

Warden, L.; Waters, C.; Sciffer, M.; Hull, A.;

Published by: Journal of Geophysical Research: Space Physics      Published on: 06/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2020JA029052

remote sensing; ULF plasma waves; Van Allen Probes; estimation; equatorial electric fields

2015

Multifrequency compressional magnetic field oscillations and their relation to multiharmonic toroidal mode standing Alfv\ en waves

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 Alfv\ en 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.

Takahashi, Kazue; Waters, Colin; Glassmeier, Karl-Heinz; Kletzing, Craig; Kurth, William; Smith, Charles;

Published by: Journal of Geophysical Research: Space Physics      Published on: 11/2015

YEAR: 2015     DOI: 10.1002/2015JA021780

Compressional oscillations; Field line resonance; Pc3-Pc4 band; plasmasphere; Van Allen Probes



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