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Found 3 entries in the Bibliography.

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Observations of kinetic scale field line resonances

We identify electromagnetic field variations from the Van Allen Probes which have the properties of Doppler shifted kinetic scale Alfv\ enic field line resonances. These variations are observed during injections of energetic plasmas into the inner magnetosphere. These waves have scale sizes perpendicular to the magnetic field which are determined to be of the order of an ion gyro-radius (ρi) and less. Cross-spectral analysis of the electric and magnetic fields reveals phase transitions at frequencies correlated with enhancements and depressions in the ratio of the electric and magnetic fields. Modeling shows that these observations are consistent with the excitation of field-line resonances over a broad range of wave numbers perpendicular to the magnetic field (k⊥) extending to k⊥ρi >> 1. The amplitude of these waves is such that E/Bo ≳ Ωi/k⊥ (E, Bo, and Ωi are the wave amplitude, background field strength, and ion gyro-frequency, respectively) leading to ion demagnetization and acceleration for multiple transitions through the wave potential.

Chaston, Christopher; Bonnell, J; Wygant, John; Mozer, Forrest; Bale, Stuart; Kersten, Kris; Breneman, Aaron; Kletzing, Craig; Kurth, William; Hospodarsky, George; Smith, Charles; MacDonald, Elizabeth;

Published by: Geophysical Research Letters      Published on: 01/2014

YEAR: 2014     DOI: 10.1002/2013GL058507

Van Allen Probes


Megavolt Parallel Potentials Arising from Double-Layer Streams in the Earth\textquoterights Outer Radiation Belt

Huge numbers of double layers carrying electric fields parallel to the local magnetic field line have been observed on the Van Allen probes in connection with in situ relativistic electron acceleration in the Earth\textquoterights outer radiation belt. For one case with adequate high time resolution data, 7000 double layers were observed in an interval of 1 min to produce a 230 000 V net parallel potential drop crossing the spacecraft. Lower resolution data show that this event lasted for 6 min and that more than 1 000 000 volts of net parallel potential crossed the spacecraft during this time. A double layer traverses the length of a magnetic field line in about 15 s and the orbital motion of the spacecraft perpendicular to the magnetic field was about 700 km during this 6 min interval. Thus, the instantaneous parallel potential along a single magnetic field line was the order of tens of kilovolts. Electrons on the field line might experience many such potential steps in their lifetimes to accelerate them to energies where they serve as the seed population for relativistic acceleration by coherent, large amplitude whistler mode waves. Because the double-layer speed of 3100 km/s is the order of the electron acoustic speed (and not the ion acoustic speed) of a 25 eV plasma, the double layers may result from a new electron acoustic mode. Acceleration mechanisms involving double layers may also be important in planetary radiation belts such as Jupiter, Saturn, Uranus, and Neptune, in the solar corona during flares, and in astrophysical objects.

Mozer, F.; Bale, S.; Bonnell, J; Chaston, C.; Roth, I.; Wygant, J.;

Published by: Physical Review Letters      Published on: 12/2013

YEAR: 2013     DOI: 10.1103/PhysRevLett.111.235002

Van Allen Probes

The Electric Field and Waves (EFW) Instruments on the Radiation Belt Storm Probes Mission

The Electric Fields and Waves (EFW) Instruments on the two Radiation Belt Storm Probe (RBSP) spacecraft (recently renamed the Van Allen Probes) are designed to measure three dimensional quasi-static and low frequency electric fields and waves associated with the major mechanisms responsible for the acceleration of energetic charged particles in the inner magnetosphere of the Earth. For this measurement, the instrument uses two pairs of spherical double probe sensors at the ends of orthogonal centripetally deployed booms in the spin plane with tip-to-tip separations of 100 meters. The third component of the electric field is measured by two spherical sensors separated by \~15 m, deployed at the ends of two stacer booms oppositely directed along the spin axis of the spacecraft. The instrument provides a continuous stream of measurements over the entire orbit of the low frequency electric field vector at 32 samples/s in a survey mode. This survey mode also includes measurements of spacecraft potential to provide information on thermal electron plasma variations and structure. Survey mode spectral information allows the continuous evaluation of the peak value and spectral power in electric, magnetic and density fluctuations from several Hz to 6.5 kHz. On-board cross-spectral data allows the calculation of field-aligned wave Poynting flux along the magnetic field. For higher frequency waveform information, two different programmable burst memories are used with nominal sampling rates of 512 samples/s and 16 k samples/s. The EFW burst modes provide targeted measurements over brief time intervals of 3-d electric fields, 3-d wave magnetic fields (from the EMFISIS magnetic search coil sensors), and spacecraft potential. In the burst modes all six sensor-spacecraft potential measurements are telemetered enabling interferometric timing of small-scale plasma structures. In the first burst mode, the instrument stores all or a substantial fraction of the high frequency measurements in a 32 gigabyte burst memory. The sub-intervals to be downloaded are uplinked by ground command after inspection of instrument survey data and other information available on the ground. The second burst mode involves autonomous storing and playback of data controlled by flight software algorithms, which assess the \textquotedbllefthighest quality\textquotedblright events on the basis of instrument measurements and information from other instruments available on orbit. The EFW instrument provides 3-d wave electric field signals with a frequency response up to 400 kHz to the EMFISIS instrument for analysis and telemetry (Kletzing et al. Space Sci. Rev. 2013).

Wygant, J.; Bonnell, J; Goetz, K.; Ergun, R.E.; Mozer, F.; Bale, S.D.; Ludlam, M.; Turin, P.; Harvey, P.R.; Hochmann, R.; Harps, K.; Dalton, G.; McCauley, J.; Rachelson, W.; Gordon, D.; Donakowski, B.; Shultz, C.; Smith, C.; Diaz-Aguado, M.; Fischer, J.; Heavner, S.; Berg, P.; Malaspina, D.; Bolton, M.; Hudson, M.; Strangeway, R.; Baker, D.; Li, X.; Albert, J.; Foster, J.C.; Chaston, C.C.; Mann, I.; Donovan, E.; Cully, C.M.; Cattell, C.; Krasnoselskikh, V.; Kersten, K.; Brenneman, A; Tao, J.;

Published by: Space Science Reviews      Published on: 11/2013

YEAR: 2013     DOI: 10.1007/s11214-013-0013-7

RBSP; Van Allen Probes