Physics
Scientific paper
Dec 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001agufmsm31b0785k&link_type=abstract
American Geophysical Union, Fall Meeting 2001, abstract #SM31B-0785
Physics
2708 Current Systems (2409), 2724 Magnetopause, Cusp, And Boundary Layers, 2740 Magnetospheric Configuration And Dynamics, 2753 Numerical Modeling, 2784 Solar Wind/Magnetosphere Interactions
Scientific paper
Magnetic impulse events (MIEs), with amplitudes ranging from several tens to several hundreds of nT and durations ranging from 5 to 20 min, are often observed in dayside high latitudes. However, there have been no consensus and few quantitative discussions so far on the generation mechanisms of MIEs. In this study we have investigated typical two MIEs with large amplitudes (> ~100nT) observed on May 22, 1996 and May 27, 1998 using the data obtained from magnetometer networks in northern and southern high latitudes and solar wind data from satellites of International Solar Terrestrial Physics program. The MIEs were accompanied by traveling convection vortices (TCVs) in northern and southern hemispheres. The triggers of these MIEs were identified as interplanetary tangential discontinuities with inward pointing motional electric field. It is found that both the propagation characteristics of these TCVs and the characteristics of the solar wind discontinuities are consistent with the expected signatures of hot flow anomalies. Then we have performed a model calculation for reproducing global magnetic disturbances due to large-amplitude MIEs. Global ionospheric currents have been calculated for a given upward and downward field-aligned current pair, assuming the current continuity through the ionosphere, and geomagnetic perturbations have been estimated from the Biot-Savart law. By comparing the result of model calculation with the current systems derived from data obtained by GOES satellite magnetometers, SuperDARN HF radars, and ground magnetometers, we propose an appropriate three-dimensional current system of MIEs. We also discuss a difference between the current system produced by MIEs and that produced by sudden impulses (SIs).
Fujiwara Hideaki
Fukunishi Hiroshi
Kataoka Ryuho
Lanzerotti Louis J.
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