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Fu H.S.,Swedish Institute of Space Physics | Cao J.B.,Beihang University | Zong Q.-G.,Beijing Institute of Technology | Lu H.Y.,Beihang University | And 3 more authors.
Journal of Atmospheric and Solar-Terrestrial Physics | Year: 2012

The role of electrons during the shock-induced chorus intensification observed by THEMIS D on 19 November 2007 is investigated in detail. First, the electrons are accelerated through the local betatron acceleration and radial diffusion, which are primarily in the perpendicular direction and result in the positive anisotropy (T ⊥>T //) of electrons; then they are scattered through the pitch-angle diffusion, during which the electron energies are partially transferred to amplify the chorus. In the case of interest, the energy loss is more efficient for the lower-energy (15keV) electrons because they have larger density gradient along the diffusion curves. The energetic electrons act as the intermediate in this scenario. They transfer the energies carried by the interplanetary shock to the chorus. The energetic electrons injected from magnetotail are not observed; they have no contributions to the energy source in this event. © 2012 Elsevier Ltd.

Fu H.S.,University of Massachusetts Lowell | Fu H.S.,State Key Laboratory for Space Weather CSSAR | Fu H.S.,University of Chinese Academy of Sciences | Tu J.,University of Massachusetts Lowell | And 6 more authors.
Journal of Geophysical Research: Space Physics | Year: 2010

We report coordinated observations of a density trough within the plasmasphere using the measurements from the radio plasma imager (RPI) and extreme ultraviolet imager (EUV) on the IMAGE satellite and the measurements from DMSP F-15. The density trough inside the plasmasphere with a width of ∼0.7 RE in terms of L shell (from L ∼ 2.3 to L ∼ 3.0) was observed in situ by RPI when IMAGE traversed the plasmasphere in ∼2130 magnetic local time (MLT) sector. The plasmasphere images taken by the IMAGE EUV instrument confirm that the density trough is inside the plasmasphere. A 2-D electron density image constructed from the RPI active sounding measurements reveals that the density trough extends along the magnetic field from the IMAGE orbit to at least 41 magnetic latitude. Meanwhile, the DMSP-F15 satellite, circling the Earth at about 850 km altitude, detected a light ion density trough at the same time on the same L shells and similar MLT sector. The coordinated observations with the IMAGE and DMSP-F15 satellite demonstrate, for the first time, that the density trough is a low-density plasmaspheric structure extending from the plasmasphere to the topside ionosphere along the geomagnetic field lines. Copyright 2010 by the American Geophysical Union.

Cao J.,Beihang University | Duan A.,State Key Laboratory for Space Weather CSSAR | Duan A.,University of Chinese Academy of Sciences | Dunlop M.,Beihang University | And 2 more authors.
Journal of Geophysical Research: Space Physics | Year: 2014

The penetration of interplanetary magnetic field (IMF) By into the magnetosphere plays an important role in determining magnetospheric configuration and its dynamics. In this paper, using 9 years of Cluster data at the center of neutral sheet, we statistically study the relations of the penetration of IMF By in the neutral sheet (NS) with IMF B z and the Kp index. The correlation coefficient between NS B y and IMF By is enhanced during the periods of southward IMF Bz and large Kp indexes. The penetration efficiency of IMF B y, which is defined as the slope of the linear fit of the points in the By-IMF By space, is larger during southward IMF B z than during northward IMF Bz. The penetration efficiency of IMF By also increases with increasing Kp index. Since the Kp index can be considered as an index of magnetospheric convection, this means that the penetration of IMF By into the magnetosphere is enhanced during the periods of strong magnetospheric convection. These results indicate that the IMF Bz and magnetospheric convection can influence the neutral sheet By and even magnetotail dynamics by changing the penetration of IMF By. ©2014. American Geophysical Union. All Rights Reserved.

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