On the nature of substorm-related transient electric field disturbances in the equatorial ionosphere
1992; Elsevier BV; Volume: 40; Issue: 1 Linguagem: Inglês
10.1016/0032-0633(92)90152-e
ISSN1873-5088
AutoresJ. H. Sastri, K. Ramesh, Daniel Karunakaran,
Tópico(s)Geomagnetism and Paleomagnetism Studies
ResumoData derived from 5-min interval ionograms of Kodaikanal (10°14′N, 77°29′E, geomag. lat. 0.6°N) on the night of 29–30 August 1957 showed the presence of a marked perturbation in F-region height (h′F) in the midnight-to-morning period. The perturbation is characterized by a sudden decrease in h′F (65 km in 1 hr, with h′F reaching a low value of 200 km) followed by a prominent increase (200 km in 75 min) over a 3-h period. Changes in h′F of essentially the same nature were also noticed at Calcutta (geomag. lat. 12.25°N) and Ahmedabad (geomag. lat. 14°N) in the same longitude sector simultaneous with those at Kodaikanal. Examination of the auroral electrojet (AE) index and magnetograms of high latitude stations widely separated in longitude revealed the prevalence of an isolated substorm of moderate strength at the time of the perturbations in equatorial F-region height. The decrease in h′F is found to occur around the onset of the substorm and the subsequent increase during the substorm recovery phase. The observed F-region height disturbance is interpreted as the signature of a transient composite disturbance in the equatorial east-west (E-W) electric field caused by the prompt penetration of substormrelated perturbations in high latitude electric fields. The nature of the electric field disturbance is in good agreement with the recent modelling results which predict a westward peturbation in E-W field at equatorial latitudes in response to an increase in polar cap potential (around the onset of a substorm) and an eastward one with a decrease in polar cap potential (during the recovery phase) in the midnight-dawn sector.
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