Latitude and local time dependences of ionospheric currents during a geomagnetic storm

Details Latitude and local time dependences of ionospheric currents during a geomagnetic storm Latitude and local time dependences of ionospheric currents during a geomagnetic storm

Dec 2007

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007agufmsa33a1054t&link_type=abstract

American Geophysical Union, Fall Meeting 2007, abstract #SA33A-1054

Other

2409 Current Systems (2721), 2721 Field-Aligned Currents And Current Systems (2409), 2760 Plasma Convection (2463), 2778 Ring Current, 2788 Magnetic Storms And Substorms (7954)

Scientific paper

In order to clarify the distribution of electric field and current in the middle- and low-latitude ionosphere during a geomagnetic storm, we analyzed ground magnetic disturbances for the storm on September 7, 2002, with the minimum SYM-H value of -168 nT. In this analysis, we investigate magnetic field deviations of the H-component from the SYM-H as functions of the magnetic latitude (MLAT) and local time (MLT). The deviation at the low latitude (10-30 degrees in MLAT) was positive and negative in the dawn and dusk sectors, respectively, during the main phase of the storm. This local time tendency represents a remarkable dawn-dusk asymmetry in the storm-time ring current. On the other hand, the deviation at the middle latitude (35-55 degrees in MLAT) was negative and positive in the morning (9-12 h MLT) and afternoon (13-15 h MLT) sectors, respectively. This tendency coincides with that of the DP2 currents. When the interplanetary magnetic field turned northward, the storm turned into the recovery phase. We found that the deviation at the middle latitudes in the early recovery phase was in opposite sense to that of the deviation during the main phase. This implies that the overshielding occurred at the middle latitudes, due to an abrupt decrease of the convection electric field associated with the recovery phase. This may suggest that the relative magnitude of the convection and shielding electric fields determines the phase of geomagnetic storm. Finally, during the late recovery phase, the dawn-dusk asymmetry both at the middle and low latitudes became weak in all magnetic local time because of symmetrized ring current. In future analysis, we should divide storm-time magnetic field variations into the origins of ring and ionospheric currents. In this talk, we will investigate the temporal and spatial developments of the latitude and local time distributions of ionospheric currents and electric field in the entire region from the magnetic equator to middle latitude.

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