Equatorial electrojet as part of the global circuit: a case-study from the IEEY

Kobea, A. T.; Amory-Mazaudier, C.; M., J.; Lühr, H.; Houngninou, E.; Vassal, J.; Blanc, E.; Curto, J. J.

doi:10.1007/s005850050639

Cited by 2 publications

(1 citation statement)

References 19 publications

(23 reference statements)

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“…Reddy et al [1979Reddy et al [ , 1981 measured a westward electric field in the daytime equatorial ionosphere with VHF backscatter radar during a substorm. The overshielding effect reduces the intensity of the equatorial electrojet on the dayside [Kobea et al, 1998Kikuchi et al, 2000aKikuchi et al, , 2000b. As a result, the negative magnetic bay associated with a substorm decreased its amplitude with latitude, but was enhanced considerably at the dayside dip equator when the ionospheric convection electric field decreased abruptly, as observed by the EISCAT radar and the auroral-to-equatorial magnetometer arrays [Kikuchi et al, 2000b].…”

Section: Introductionmentioning

confidence: 99%

Equatorial counterelectrojets during substorms

Kikuchi¹,

Hashimoto²,

et al. 2003

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Equatorial counterelectrojet (CEJ) events are analyzed in association with changes in the interplanetary magnetic field (IMF), polar cap potential (PCP), and electric field measured in the equatorial ionosphere. In one event on 16 July 1995, the equatorial CEJ was observed at the afternoon dip equator during the recovery phase of the substorm when the IMF turned northward. Rapid decreases in the PCP and in the auroral electrojet occurred simultaneously with the equatorial CEJ, suggesting instantaneous equatorward penetration of the rapid decrease in the electric field associated with the region 1 field‐aligned currents (R1 FACs) under the condition of a well‐developed shielding electric field due to the R2 FACs. In the other event on 8 April 1993, the equatorial CEJ associated with the northward turning of the IMF was directly related to a rapid decrease in the equatorial electric field measured by the Jicamarca incoherent scatter radar as well as to a decrease in the PCP. We confirm the scenario for the substorm‐associated equatorial CEJ as caused by the dominant R2 FACs when the R1 FACs decrease abruptly because of the northward turning of the IMF. We also suggest that the DP 1 current system is composed of the Hall currents surrounding the R2 FACs and the equatorial CEJ closing with the R2 FACs, which are superposed on the DP 2 currents caused by the R1 FACs, being dominant when the IMF turns northward. The coherent occurrence of the electric field in the F region with the electric current in the E region at the equator is explained by applying the Earth‐ionosphere waveguide model of Kikuchi and Araki [1979b] as a most promising transmission mechanism. All the conditions for the equatorial CEJ most likely occur during the substorm, but the northward turning of the IMF and the resultant decrease in the PCP play a crucial role under the condition of well‐developed R2 FACs.

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Section: Introductionmentioning

confidence: 99%

Equatorial counterelectrojets during substorms

Kikuchi¹,

Hashimoto²,

et al. 2003

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Including gap region field‐aligned currents and magnetospheric currents in the MHD calculation of ground‐based magnetic field perturbations

Ridley

Welling

et al. 2010

J. Geophys. Res.

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[1] Many high-latitude modeling studies utilize the horizontal ionospheric Hall current in calculating ground-based magnetic perturbations, but low-latitude and midlatitude studies should include current systems such as the magnetospheric, field-aligned, and Pedersen currents. Recently, by including all these current systems, a more precise groundbased perturbation calculator has been implemented in the Space Weather Modeling Framework. Using this new method, ground-based perturbations generated by different current systems are analyzed at low, middle, and high latitudes. As a result of the current systems, MLT-UT maps of ground-based perturbations are studied. Furthermore, nine storms events are simulated at more than 20 low-latitude and midlatitude magnetometer locations and compared with observational ground-based perturbations. These studies show that for specifying the northward component of the ground magnetic perturbations, the inclusion of magnetospheric, field-aligned, and Pedersen current is important and improves the prediction significantly over the prediction only considering the Hall current in the calculation. The improvement is the most during the storm main phase. However, for the vertical and eastward components of the perturbations, which were typically smaller than the northward component, the inclusion of these current systems actually made the specifications worse because the ring current in the model rotates more toward the dayside than in reality.

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Equatorial electrojet as part of the global circuit: a case-study from the IEEY

Cited by 2 publications

References 19 publications

Equatorial counterelectrojets during substorms

Equatorial counterelectrojets during substorms

Including gap region field‐aligned currents and magnetospheric currents in the MHD calculation of ground‐based magnetic field perturbations

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