HR: 14:55h
AN: SA42B-06
TI: The Response of the Magnetosphere to an Interplanetary Shock: Ground-based Observations 
    of the Sudden Impulse on September 24, 1998
AU: Zesta, E 
EM:
AF: Institute of Geophysics and Planetary Physics,
    University of California Los Angeles, CA 90095-1567  United States
AU: * Chi, P J
EM: pchi@igpp.ucla.edu
AF: Institute of Geophysics and Planetary Physics,
    University of California Los Angeles, CA 90095-1567  United States
AU: Russell, C T
EM:
AF: Institute of Geophysics and Planetary Physics,
    University of California Los Angeles, CA 90095-1567  United States
AU: Raeder, J 
EM:
AF: Institute of Geophysics and Planetary Physics,
    University of California Los Angeles, CA 90095-1567  United States
AU: Le, G 
EM:
AF: Institute of Geophysics and Planetary Physics,
    University of California Los Angeles, CA 90095-1567  United States
AU: Yumoto, K 
EM:
AF: Department of Earth and Planetary Sciences,
    Kyushu University 33,
    6-10-1 Hakozaki Fukuoka, 812-8581  Japan
AU: Kawano, H 
EM:
AF: Department of Earth and Planetary Sciences,
    Kyushu University 33,
    6-10-1 Hakozaki Fukuoka, 812-8581  Japan
AU: Kitamura, K 
EM:
AF: Department of Earth and Planetary Sciences,
    Kyushu University 33,
    6-10-1 Hakozaki Fukuoka, 812-8581  Japan
AU: Angelopoulos, V 
EM:
AF: Space Sciences Laboratory,
    University of California Berkeley, CA 94720  United States
AU: Moldwin, M 
EM:
AF: Florida Institute of Technology,
    Physics and Space Sciences,
    150 W. University Blvd Melbourne, FL 32901  United States

AB: The strong interplanetary shock wave that 
    intersected the magnetosphere at about 2344 UT 
    on September 24, 1998, launched a compression 
    of the magnetosphere that was followed around 
    the globe by a new generation of magnetometers 
    with rapid sampling and precise GPS-synchronized 
    timing. Magnetometers of these chains included 
    those in the Circum-pan Pacific Magnetometer 
    Network (CPMN), those in the IGPP/LANL array, 
    those in the MEASURE array and those in the MACCS 
    array. The event exhibited all the classical 
    signatures of an SI including the preliminary 
    decrease before the main increase in the 
    H-component. A preceding depression of the magnetic 
    field with an amplitude of 1--2 nT also occurred 
    approximately 40 seconds prior to the preliminary 
    impulse at some low-latitude stations near local
    noon. Properties of the SI signatures on the ground,
    including the propagation of the preliminary 
    impulse, will be presented. The ability to model 
    this event and its induced ionospheric currents 
    using an MHD code allows us to compare the 
    compression as it is seen in the magnetosphere 
    with the response of the ionospheric currents.
DE: 2139  Interplanetary shocks
DE: 2740  Magnetospheric configuration and dynamics
DE: 2784  Solar wind/magnetosphere interactions
SC: SA
MN: 1999 Spring Meeting