HR: 16:45h
AN: SM22D-04    [PDF]
TI: Periodic magnetospheric substorms and their relationship with solar wind pressure variations
AU: * Huang, C
EM: cshuang@haystack.mit.edu
AF: Haystack Observatory, Massachusetts Institute of Technology, Route 40, Westford, MA 01886 United States
AU: Foster, J
AF: Haystack Observatory, Massachusetts Institute of Technology, Route 40, Westford, MA 01886 United States
AU: Reeves, G
AF: Los Alamos National Laboratory, Mail Stop D-466, Los Alamos, NM 87545 United States
AU: Le, G
AF: NASA Goddard Space Flight Center, Laboratory for Extraterrestrial Physics, Greenbelt, MD 20771 United States
AU: Frey, H
AF: University of California, Space Science Laboratory, Berkeley, CA 94720 United States
AU: Pollock, C
AF: Southwest Research Institute, Department of Space Science, San Antonio, TX 78228 United States
AB: Outstanding problems in magnetospheric substorms include what causes substorm onsets and whether substorms have some specific periodicity. We will present observations and interpretation that are related to the above problems. In one event, the Geotail satellite was located in the near tail between X = -20 and -30 Re and detected periodic southward turnings of the magnetospheric magnetic field. Geosynchronous satellites measured sawtooth-like injections of energetic charged fluxes from the tail. The IMAGE satellite measured enhanced emissions of energetic neutral atoms in the ring current and auroral brightenings. The CANOPUS photometers measured intensifications and latitudinal motion of auroral emissions. These magnetospheric and ionospheric phenomena have the same periodicity and indicate the occurrence of periodic substorms. Several other events show similar phenomena. The periodic substorms have periods of 2-3 hours and occur after a solar wind pressure impulse impinges on the magnetosphere. We suggest that magnetospheric substorms have an intrinsic cycle time of 2-3 hours. If solar wind pressure oscillations with periods comparable to the substorm cycle time are imposed on the magnetosphere, some magnetospheric resonant state may be excited, and periodic substorms can be triggered. Otherwise, if the solar wind oscillates too fast, no enough energy is accumulated in the magnetotail for substorms to occur; if the period of solar wind pressure oscillations is too long, magnetospheric energy may be released through other processes including internally triggered substorms.
DE: 2730 Magnetosphere--inner
DE: 2744 Magnetotail
DE: 2784 Solar wind/magnetosphere interactions
DE: 2788 Storms and substorms
SC: SPA - Magnetospheric Physics [SM]
MN: 2003 Fall Meeting