Physics
Scientific paper
Jun 1988
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1988jgr....93.5624k&link_type=abstract
Journal of Geophysical Research (ISSN 0148-0227), vol. 93, June 1, 1988, p. 5624-5640.
Physics
108
Auroral Arcs, Ionospheric Currents, Magnetosphere-Ionosphere Coupling, Polar Substorms, Atmospheric Circulation, Atmospheric Models, Computerized Simulation, Field Aligned Currents, Night Sky, Polar Regions
Scientific paper
A theory that accounts for the causes of a substorm onset and subsidence is developed on the basis of the magnetosphere-ionosphere coupling model of Kan and Sun (1985). It is shown that an enhanced magnetospheric convection can produce a narrow belt of intense upward field-aligned current, leading to auroral substorm onset in about 40 min after a southward turning of the IMF. The two necessary conditions for substorm are that the polar cap potential must exceed a certain value and that the convection reversal region must overlap with the poleward gradient of the diffuse auroral conductance in the ionosphere in the midnight sector. The matching ensures that the divergence of the Pedersen current colocates with the divergence of the Hall current, to maximize the upward field-aligned current near the poleward boundary of the diffuse aurora in the midnight sector. When one of the two conditions is no longer satisfied, substorm subsides.
Akasofu Syuh-Ichi
Kan Joseph R.
Zhu Lijun
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