Evolution of the plasmapause position

The Polar spacecraft, launched in February 1996, has crossed the plasmapaus e more than 6000 times so that a large number of plasmapause measurements a re available at all local time sectors, at low (similar to 1R(E)) and high (similar to2-4R(E)) altitudes, and during various magnetic conditions. Usin g sequential plasmapause crossings, we have studied the evolution of the pl asmapause position in a few specific local time sectors. Near the dawn-dusk meridian, the duskside plasmapause is approximately 1-3L shell farther fro m the Earth than the dawnside plasmapause, but the evolution of the plasmap ause position is quite similar and simultaneous at both sides. Near the noo n-midnight meridian, the plasmapause is located approximately at the same d istance on both sides of the Earth, and the evolution is again similar and synchronous with no clear time delay at both sides. After an SSC, the noons ide plasmapause is found to propagate earthward about one L shell in 5 h. ( C) 2001 Elsevier Science Ltd. AH rights reserved.