Storm-time electric fields in the mid-latitude ionosphere observed by ground magnetometers and the Akebono satellite

Details Storm-time electric fields in the mid-latitude ionosphere observed by ground magnetometers and the Akebono satellite Storm-time electric fields in the mid-latitude ionosphere observed by ground magnetometers and the Akebono satellite

Dec 2008

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agufmsm53a1672t&link_type=abstract

American Geophysical Union, Fall Meeting 2008, abstract #SM53A-1672

Physics

2409 Current Systems (2721), 2712 Electric Fields (2411), 6929 Ionospheric Physics (1240, 2400), 7524 Magnetic Fields, 7954 Magnetic Storms (2788)

Scientific paper

The mid-latitude ionosphere electromagnetically connected to the inner magnetosphere via magnetic field lines is an important region for understanding storm-time magnetosphere-ionosphere coupling processes. In order to clarify distributions of electric fields and currents in the mid- and low-latitude ionosphere during storms, we investigated latitudinal and local time dependence of magnetic field variations for six storms using a ground magnetometer network covering from high to equatorial latitudes. The analysis results suggested that competition between convection and shielding electric fields controlled characteristics of magnetic disturbances caused by mid-latitude ionospheric currents. However, a quantitative relationship between ground magnetic disturbances and in-situ ionospheric electric fields has not been clarified yet because of difficulties in deducing electric fields from magnetic field variations. Therefore, in this study, we analyzed ground magnetic disturbances and electric field mapped onto the ionosphere observed by the Akebono satellite during the storm occurred on February 21-22, 1994, with a minimum SYM-H value of -152 nT. During the main phase of the storm, the satellite passed through a region from 73 degrees invariant latitude (ILAT) and 10 magnetic local time (MLT) to 49 degrees ILAT and 18 MLT from 0055 to 0148 UT. The poleward electric field changed negative to positive values at 65.5 degrees ILAT (15 MLT). The electric field signature indicates that the center of region-1 field-aligned currents (R-1 FACs) was located at this latitude. Subsequently, the electric field profile showed two peaks at 62-63 degrees ILAT (15.5 MLT) and 55 degrees ILAT (17 MLT). The former corresponds to the auroral oval identified by the lower energy particle instrument of the Akebono. On the other hand, during the same period, we also investigated the latitudinal distribution of the northward magnetic field variation measured on the ground (16.5-19.5 MLT). The analysis result shows centers of R-1 FACs and auroral electrojet were located at 67.5 and 62.5 degrees in corrected geomagnetic latitude, respectively. This is consistent with each current position deduced from the electric field observed by the Akebono satellite. This fact indicates that there is a possibility of quantitative derivations of ionospheric electric fields using magnetic field variations measured on the ground.

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