Penetration of magnetospheric electric fields to low latitude during geomagnetic storms

Details Penetration of magnetospheric electric fields to low latitude during geomagnetic storms Penetration of magnetospheric electric fields to low latitude during geomagnetic storms

Dec 2009

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufmsa23b1479k&link_type=abstract

American Geophysical Union, Fall Meeting 2009, abstract #SA23B-1479

Physics

[2409] Ionosphere / Current Systems, [2411] Ionosphere / Electric Fields, [2415] Ionosphere / Equatorial Ionosphere, [2788] Magnetospheric Physics / Magnetic Storms And Substorms

Scientific paper

Penetration of the magnetospheric electric fields to low latitude ionosphere is examined using magnetometer data from high latitude to the equator for geomagnetic storms characterized by an equatorial enhancement of storm amplitude. To detect the penetrated electric fields, we analyze magnetic disturbances at the geomagnetic equator, Yap (-0.3° GML), subtracted by those at low latitude, Okinawa (14.47° GML). During storm main phase, the equatorial electrojet (EEJ) is enhanced by the dawn-to-dusk convection electric field associated with the Region-1 field-aligned currents (R1 FACs). The excess part of the stormtime EEJ relative to the quiettime EEJ is an equatorial part of the global DP 2 currents driven by the convection electric field. Quick development of the global DP 2 currents suggests an instantaneous transmission of the convection electric field from the polar to equatorial ionosphere. An electric field associated with the ionospheric currents is then transmitted to the F-region ionosphere, and causes quick response of the low latitude ionosphere to the enhancement of the polar cap potential. The electric field penetration continues for several hours during the whole period of storm main phase, but shielding becomes effective in late main phase because of development of the R2 FACs. The shielding electric field becomes dominant, i.e., overshielding occurs at the beginning of storm recovery phase, causing the stormtime counter-electrojet (CEJ) at the dayside equator. On the other hand, there occasionally occurs CEJs during storm main phase. This type of CEJ could be caused by the disturbance dynamo or by stormtime substorms. The electric field responsible for the CEJ still remains a crucial issue in understanding the stormtime electric fields at low latitude.

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