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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 33, issue 1
Ann. Geophys., 33, 39–46, 2015
https://doi.org/10.5194/angeo-33-39-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 33, 39–46, 2015
https://doi.org/10.5194/angeo-33-39-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

ANGEO Communicates 12 Jan 2015

ANGEO Communicates | 12 Jan 2015

The nightside magnetic field line open–closed boundary and polar rain electron energy-latitude dispersion

S. Wing and Y. L. Zhang S. Wing and Y. L. Zhang
  • The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, USA

Abstract. The polar rain electrons near the open–closed field line boundary on the nightside often exhibit energy-latitude dispersion, in which the energy decreases with decreasing latitude. The solar wind electrons from the last open-field line would E × B drift equatorward as they move toward the ionosphere, resulting in the observed dispersion. This process is modeled successfully by an open-field line particle precipitation model. The existing method for determining the magnetotail X line distance from the electron dispersion underestimates the electron path length from the X line to the ionosphere by at least 33%. The best estimate of the path length comes from using the two highest energy electrons in the dispersion region. The magnetic field line open–closed boundary is located poleward of the highest energy electrons in the dispersion region, which in turn is located poleward of Defense Meteorological Satellite Program (DMSP) b6, b5e, and b5i boundaries. In the four events examined, b6 is located at least 0.7–1.5° equatorward of the magnetic field line open–closed boundary. The energy-latitude dispersion seen in the electron overhang may result from the plasma sheet electron curvature and gradient drifts into the newly closed field line.

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Short summary
Magnetotail reconnection and E×B leads to dispersion in polar rain electrons. APL-OPM successfully models the polar rain energy-latitude dispersion. The magnetic field line open-closed boundary is located poleward of the auroral oval.
Magnetotail reconnection and E×B leads to dispersion in polar rain electrons. APL-OPM...
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