Ionospheric Electric Field Perturbations at the Nightside Equator Associated With a Geomagnetic Sudden Commencement

Details Ionospheric Electric Field Perturbations at the Nightside Equator Associated With a Geomagnetic Sudden Commencement Ionospheric Electric Field Perturbations at the Nightside Equator Associated With a Geomagnetic Sudden Commencement

Dec 2002

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002agufmsm12a0458s&link_type=abstract

American Geophysical Union, Fall Meeting 2002, abstract #SM12A-0458

Physics

2411 Electric Fields (2712), 2708 Current Systems (2409), 2736 Magnetosphere/Ionosphere Interactions, 2788 Storms And Substorms

Scientific paper

Ionospheric electric field perturbations associated with a sudden commencement at 1640 UT Apr. 6, 2000 were observed by the FM-CW HF radar at the dip equator station Cebu, Philippine. Ionograms were obtained from the FM-CW HF radar at intervals of 5 minutes. The zonal electric field can be estimated from the time variation of the height profile of ionograms. A sudden increase in the westward electric field of 1.6 mV/m was observed simultaneously with the sudden increases in the H component magnetic field of 250 and 110 nT at the dayside dip equatorial station Ancon, Peru and the dayside off dip equatorial station Eusebio, Brazil, respectively. The amplitude enhancement of the magnetic variation at the dip equator suggest that an eastward electric field was imposed at the dayside equatorial ionosphere. Both the dayside and nightside electric field perturbations show that the dawn to dusk electric field of DP(MI) was imposed globally on the equatorial ionosphere. The HF Doppler frequency shift was observed at the nightside low latitude station Sugadaira, Japan. From the frequency deviation, it is found that a westward electric field of 2.0 mV/m was suddenly imposed at the beginning of the sc. The amplitude of the westward electric field observed at the nightside equator is 0.8 times that at the nightside low latitude station. It can be caused by the geometrical attenuation [Kikuchi et al., 1978, Nature]. The direction of the zonal electric field observed at Cebu was reversed from westward to eastward and returned westward again. The electric field at Sugardaira shows similar temporal variations. These variations were well correlated with fluctuations of solar wind number density. The eastward electric field may be caused by the over shielding effect of the region 2 field-aligned current [Kikuchi et al., 2000, JGR]. Acknowledgement. The HF Doppler data was provided by Sugadaira Space Radio Observatory, Univ. Electro-Comm.

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