Low latitude signatures of substorm activity

Rostoker, G.

doi:10.1016/0021-9169(93)90092-d

Cited by 7 publications

(2 citation statements)

References 42 publications

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“…Moreover, in the course of the development of a magnetospheric substorm, the DP 2 type current develops during the growth phase and remains even during the expansion phase [Clauer and Kamide, 1985;Kamide, 1991]. Thus deeper understanding of the DP 2 would be very important for the study of the substorm processes [Rostoker, 1993] and for the study of the equatorial magnetic and ionospheric disturbances related to the magnetospheric electric field [Gonzales et al, , 1983Kelley et al, 1979;Spiro et al, 1988;Fejer et al, 1990]. Although there have been quite a bit studies of the electric field and currents of the high-latitude DP 2 [e.g., Brathwaite and Rostoker, 1981;Clauer and Kamide, 1985], little studies of the equatorial DP 2 have been performed since the pioneering works of Nishida and his colleagues whose conclusions were based on normal-run magnetograms with a time resolution of the order of 1 min.…”

Section: Introductionmentioning

confidence: 99%

Direct penetration of the polar electric field to the equator during a DP 2 event as detected by the auroral and equatorial magnetometer chains and the EISCAT radar

Kikuchi¹,

Lühr²,

Kitamura³

et al. 1996

J. Geophys. Res.

265

316

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The quasi‐periodic DP 2 magnetic fluctuations (period of 30–40 min) appearing coherently at the auroral and equatorial latitudes during the day are analyzed based on the high time resolution magnetometer data recorded at the International Monitor for Auroral Geomagnetic Effects (IMAGE) stations in Scandinavia and at the Brazilian and African equatorial stations. It is shown that the correlation between the DP 2 magnetic fluctuations at both latitudes is excellent (correlation coefficient of 0.9). No discernible time shift has been found within the resolution of 25 s. The European incoherent scatter (EISCAT) radar observations in Scandinavia show that the DP 2 fluctuations at auroral latitudes are caused by an ionospheric Hall current which is controled by the convection electric field. The DP 2 fluctuations exhibit a strong decrease in magnitude with decreasing latitude, however, it is enhanced considerably at the dip equator with an amplitude comparable to that at the subauroral latitude. The considerable equatorial enhancement of the magnitude of the DP 2 fluctuations with an enhancement ratio of 4 is due to the concentration of the electric current along the highly conductive dayside equatorial ionosphere. These observational facts can be explained in terms of an ionospheric current which is generated by the magnetospheric electric field at the high latitude and extends to the equatorial ionosphere almost instantaneously. From the viewpoint of the electric field penetration, we conclude that the magnetospheric electric field penetrates to the equatorial ionosphere through the polar ionosphere almost instantaneously within the time resolution of 25 s. The nearly instantaneous propagation of the electric field to the equator can be explained primarily by a parallel plane transmission line model composed of the conductive Earth and ionosphere. In addition to our finding of the fast propagation of the DP 2 electric field, it is found that an impulsive magnetic change with a timescale of 100 s appears at the dayside dip equator with a time delay of about 10 s, which requires to include the effect of the high conductivity of the dayside equatorial ionosphere in future studies of the propagation model.

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Section: Introductionmentioning

confidence: 99%

Direct penetration of the polar electric field to the equator during a DP 2 event as detected by the auroral and equatorial magnetometer chains and the EISCAT radar

Kikuchi¹,

Lühr²,

Kitamura³

et al. 1996

J. Geophys. Res.

265

316

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“…Detailed evaluation of the local time dependence of the characteristics of equatorial DP2 will help advance our understanding of the substorm phenomenon as a whole (Rostoker, 1993) and of related equatorial ionospheric disturbances (see, Fejer, 1997 and references therein). We have very recently found evidence for DP2 electric ®eld¯uctuations (period 25 min) at the duskside dip equator which supports the view that the magnetospheric electric ®eld responsible for DP2 penetrates to equatorial ionosphere on the duskside as on the dayside and leads to electric ®eld perturbations of the same polarity (eastward) as on the dayside (Abdu et al, 1998).…”

Section: Introductionmentioning

confidence: 99%

Letter to the editor: Electric field fluctuations (25-35 min) in the midnight dip equatorial ionosphere

et al. 2000

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Abstract. Measurements with a HF Doppler sounder at Kodaikanal (10.2°N, 77.5°E, geomagnetic latitude 0.8°N) showed conspicuous quasi-periodic¯uctuations (period 25±35 min) in F region vertical plasma drift, V z in the interval 0047±0210 IST on the night of 23/24 December, 1991 (A p = 14, K p < 4 ) ). The¯uctuations in F region vertical drift are found to be coherent with variations in B z (north-south) component of interplanetary magnetic ®eld (IMF), in geomagnetic H/X components at high-mid latitude locations both in the sunlit and dark hemispheres and near the dayside dip equator, suggestive of DP2 origin. But the polarity of the electric ®eld¯uctuations at the midnight dip equator (eastward) is the same as the dayside equator inferred from magnetic variations, contrary to what is expected of equatorial DP2. The origin of the coherent occurrence of equatorial electric ®eld¯uctuations in the DP2 range of the same sign in the day and night hemispheres is unclear and merits further investigations.

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Large-scale fields and flows in the magnetosphere-ionosphere system

Lockwood

1995

Surv Geophys

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Low latitude signatures of substorm activity

Cited by 7 publications

References 42 publications

Direct penetration of the polar electric field to the equator during a DP 2 event as detected by the auroral and equatorial magnetometer chains and the EISCAT radar

Direct penetration of the polar electric field to the equator during a DP 2 event as detected by the auroral and equatorial magnetometer chains and the EISCAT radar

Letter to the editor: Electric field fluctuations (25-35 min) in the midnight dip equatorial ionosphere

Large-scale fields and flows in the magnetosphere-ionosphere system

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