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| Titel |
Signatures of storm sudden commencements in geomagnetic H, Y and Z fields at Indian observatories during 1958-1992 |
| VerfasserIn |
R. G. Rastogi |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 17, no. 11 ; Nr. 17, no. 11, S.1426-1438 |
| Datensatznummer |
250013835
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| Publikation (Nr.) |
 copernicus.org/angeo-17-1426-1999.pdf |
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| Zusammenfassung |
The work describes an intensive study of
storm sudden commencement (SSC) impulses in horizontal (H), eastward (Y) and
vertical (Z) fields at four Indian geomagnetic observatories between 1958–1992.
The midday maximum of ΔH has been shown to exist even at the
low-latitude station Alibag which is outside the equatorial electrojet belt,
suggesting that SSC is associated with an eastward electric field at equatorial
and low latitudes. The impulses in Y field are shown to be linearly and
inversely related to ΔH at Annamalainagar and Alibag. The average SC
disturbance vector is shown to be about 10–20°W of the geomagnetic meridian.
The local time variation of the angle is more westerly during dusk hours in
summer and around dawn in the winter months. This clearly suggests an effect of
the orientation of shock front plane of the solar plasma with respect to the
geomagnetic meridian. The ΔZ at SSC have a positive impulse as in
ΔH. The ratio of ΔZ/ΔH are abnormally large
exceeding 1.0 in most of the cases at Trivandrum. The latitudinal variation of
ΔZ shows a tendency towards a minimum over the equator during the
nighttime hours. These effects are explained as (1) resulting from the
electromagnetic induction effects due to the equatorial electrojet current in
the subsurface conducting layers between India and Sri Lanka, due to channelling
of ocean currents through the Palk Strait and (2) due to the concentration of
induced currents over extended latitude zones towards the conducting graben
between India and Sri Lanka just south of Trivandrum.
Key words. Interplanetary physics (interplanetary
shocks) · Ionosphere (equatorial ionosphere) · Magnetospheric physics (storms
and substorms) |
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