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The plasmapause formation seen from meridian perspective by KAGUYA
Author(s) -
Murakami Go,
Yoshioka Kazuo,
Yamazaki Atsushi,
Nishimura Yukitoshi,
Yoshikawa Ichiro,
Fujimoto Masaki
Publication year - 2016
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2016ja023377
Subject(s) - plasmasphere , magnetosphere , geophysics , earth's magnetic field , physics , convection , van allen probes , electric field , whistler , astrophysics , geology , van allen radiation belt , magnetic field , mechanics , quantum mechanics
Observations by the extreme ultraviolet (EUV) imager on board the IMAGE spacecraft revealed that the formation of a sharp plasmapause occurs in the postmidnight sector soon (<1 h) after the convection enhancement. These results cannot be explained simply by the conventional theory of the plasmapause formation that the plasmapause coincides with the last closed equipotential of the convection electric field superposed on the Earth's corotation electric field. However, due to the limitation that the EUV imager provides information on only the azimuthal distribution of the plasmapause, the formation mechanism still remains an open issue. Now global images of the plasmasphere from meridian perspective become available, thanks to the telescope of extreme ultraviolet (TEX) instrument on board the KAGUYA spacecraft. Here we studied the plasmapause formation mechanism by analyzing the sequential TEX images of an erosion event during the geomagnetic disturbance ( Kp = 5) on 1–2 May 2008. The temporal evolution of the plasmapause locations at postmidnight observed by TEX agreed with those predicted by the dynamic simulations based on the interchange mechanism. Furthermore, the He + column density in the nightside plasmasphere decreased by ~30% only at the low latitudes (<20°) during the enhanced convection period. This suggests that the plasmapause formation occurs first near the equatorial region during a geomagnetic disturbance, and it agrees with the plasmapause formation mechanism based on the interchange instability. Although we cannot conclude exclusively for the interchange mechanism, this is the first study to present the plasmapause formation viewed from the meridian perspective.