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Title: | Penetration electric fields at the nightside dip equator associated with the main impulse of the storm sudden commencement of 8 July 1991 |
Authors: | Sastri, J. H |
Keywords: | Ionosphere: Electric Fields (2712) Ionosphere: Current Systems (2708) Ionosphere: Equatorial Ionosphere Ionosphere: Ionosphere/Magnetosphere Interactions (2736) |
Issue Date: | Dec-2002 |
Publisher: | American Geophysical Union |
Citation: | Journal of Geophysical Research-Space Physics, Vol. 107, No. A 12, pp. SIA 9 - 1, CiteID 1448 |
Abstract: | The geomagnetic storm sudden commencement (ssc) of 8 July 1991 was reported [Wilson et al., 2001] to be characterized by a reduction (enhancement) of X component at midlatitudes in the noon (midnight) sector in the 1-hour period after its start at 1636 UT. This distinctive feature is seen even after accounting for the effects of the Chapman-Ferraro current by subtracting the step-like increase of X/H component at low-latitude stations on the same magnetic meridian from the midlatitude data. We present evidence to show that over the same 1-hour period after the start of the ssc on 8 July 1991 an eastward electric field disturbance (peak value ~1.2 mV/m) grew up and decayed at the premidnight dip equator. The eastward electric field evidenced at the nightside dip equator is interpreted as the signature of the penetration of the dawn-to-dusk electric field associated with an enhancement of region 1 field-aligned currents (FACs) driven by the solar wind. The negative disturbance in the H/X component at midlatitudes in the noon sector is explained as the magnetic effect of FACs that carry the large-scale electric fields from the magnetosphere to the polar ionosphere as well as the disturbance of polar origin-type 2 ionospheric currents excited by the large-scale electric field. |
Description: | Open Access |
URI: | http://hdl.handle.net/2248/2985 |
ISSN: | 0148-0227 |
Appears in Collections: | IIAP Publications |
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Penetration electric fields at the nightside dip equator associated... | Open Access | 420.14 kB | Adobe PDF | ![]() View/Open |
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