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Earth Planets Space, Vol. 54 (No. 9), pp. e1-e4, 2002

E-LETTER

A satellite magnetometer observation of dusk-to-dawn current in the midnight magnetosphere at low-latitude Pi2 onset

O. Saka1, H. Akaki2, and D. N. Baker3

1Department of Physics, Kurume National College of Technology, Kurume 830-8555, Japan
2Department of Earth and Planetary Science, Kyushu University, Fukuoka 812-8581, Japan
3Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80309, U.S.A.

(Received June 13, 2002; Revised August 25, 2002; Accepted September 11, 2002)

Abstract: A multiple Pi2 event was observed in the midnight sector at the low-latitude ground magnetometer station. Meanwhile, particle fluxes in the midnight sector were measured during the multiple Pi2 event by the AMPTE/CCE spacecrafts in the L range from 4.8 to 5.8 and by geosynchronous satellite, S/C1984-129, at the dawn sector. We present an examination of the magnetic field changes and the associated particle behavior during the multiple Pi2 event. We argue that the temporal intensification of the dusk-to-dawn currents near the geosynchronous altitudes may trigger the Pi2 pulsations. The plasmas injected in the inner magnetosphere are possible candidate for driving the dusk-to-dawn currents.
key words: Low-latitude Pi2, current system, midnight magnetosphere, substorm onset, particle injection.


Corresponding author E-mail: saka@kurume-nct.ac.jp


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