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Propagation of ULF waves from the upstream region to the midnight sector of the inner magnetosphere
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2016
Source: Journal of Geophysical Research-Space Physics, 121(9), 8428-8447.
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Journal Title:Journal of Geophysical Research: Space Physics
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Description:Ultralow frequency (ULF) waves generated in the ion foreshock are a well-known source of Pc3-Pc4 waves (7-100mHz) observed in the dayside magnetosphere. We use data acquired on 10 April 2013 by multiple spacecraft to demonstrate that ULF waves of upstream origin can propagate to the midnight sector of the inner magnetosphere. At 1130-1730 UT on the selected day, the two Van Allen Probes spacecraft and the geostationary ETS-VIII satellite detected compressional 20 to 40mHz magnetic field oscillations between L approximate to 4 and L approximate to 7 in the midnight sector, along with other spacecraft located closer to noon. Upstream origin of the oscillations is concluded from the wave frequency that matches a theoretical model, globally coherent amplitude modulation, and duskward propagation that is consistent with expected entry of the upstream wave energy through the dawnside flank under the observed interplanetary magnetic field. The oscillations are attributed to magnetohydrodynamic fast-mode waves based on their propagation velocity of approximate to 300km/s and the relationship between the electric and magnetic field perturbations. The magnitude of the azimuthal wave number is estimated to be approximate to 30. There is no evidence that the oscillations propagated to the ground in the midnight sector.
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Source:Journal of Geophysical Research-Space Physics, 121(9), 8428-8447.
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