Observations of substorms during prolonged northward IMF conditions

C.-C. Wu, K. Liou, R. P. Lepping, G. Le, and C.-I Meng

NRC, Laboratory for Extraterrestrial Physics, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771


Substorms have long been considered as an energy dissipation process resulting from a specific solar wind-magnetosphere coupling. Whether the energy dissipation process is associated with a directly driven or a loading-unloading process, a prerequisite of these two current substorm models is the needed or required energy input from the solar wind. A southward interplanetary magnetic field (IMF) seems generally to be the most favorite one, because under this condition solar wind energy can be very effectively transferred into the magnetosphere by magnetic field line merging. Hence, a northward IMF is not likely to result in a substorm. Indeed, until now there has not been documented a case of a substorm occurring during a prolonged northward IMF condition. Nevertheless, here we report such a case by using solar wind plasma and magnetic field data recorded by WIND, global auroral image data acquired by Polar, and ground magnetic field data from an array of magnetometers.

submitted to Proceedings of the ICST-6 Conference, 2002