Global evolution of a substorm-associated DP2 current system observed by superDARN and magnetometers

Kikuchi, Takashi; Pinnock, M.; Rodger, A.; Luehr, H.; Kitamura, Teitaro; Tachihara, H.; Watanabe, Masakazu; Sato, Natsuo; Ruohoniemi, M.

doi:10.1016/s0273-1177(99)01037-6

Cited by 26 publications

(40 citation statements)

References 4 publications

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“…Quite a few substorms are triggered by the northward turning of the IMF [ Rostoker et al , 1980; Lyons , 1995]. In the first event analyzed, the substorm commenced at around 1455 UT on 16 July 1995, as determined by the injection of energetic particles in 0200 MLT and by a sudden onset of absorption in the morning sector [ Kikuchi et al , 2000a]. There is no clear signature in the IMF that triggered the substorm, although the H component of the magnetic field at Thule changed its temporal behavior from the steep decrease to a gradual increase at the onset of the substorm (Figure 1).…”

Section: Summary and Discussionmentioning

confidence: 99%

“… Reddy et al [1979, 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 , 1998, 2000; Kikuchi et al , 2000a, 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%

“…These observations enable us to extend the DP 1 currents to mid and low latitudes, particularly to the dayside dip equator. Kikuchi et al [2000a] pointed out that the enhanced negative bay at the equator could appear as the equatorial CEJ, and suggested that the northward turning of the IMF caused the equatorial CEJ under the condition of well‐developed R2 FACs.…”

Section: Introductionmentioning

confidence: 99%

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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: Summary and Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Equatorial counterelectrojets during substorms

Kikuchi¹,

Hashimoto²,

et al. 2003

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“…The resulting convection electric fields and DP2 currents were observed to penetrate to the equatorial ionosphere during the substorm growth phase Fejer et al, 1979;Gonzales et al, 1979;Somayajulu et al, 1987;Kikuchi et al, 2000a]. Quasi periodic DP2 magnetic fluctuations are caused by the convection electric fields controlled by the IMF [Nishida, 1968].…”

Section: Introductionmentioning

confidence: 99%

Low-latitude ionospheric-thermospheric response to storm time electrodynamical coupling between high and low latitudes

et al. 2011

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“…This expansion is faster than the magnetosphere can respond, so that the high-latitude convection electric fields penetrate into the low-latitude ionosphere (e.g., Kelley et al, 1979;Kikuchi et al, 2000;Huang et al, 2007;Kikuchi et al, 2008). During the magnetic storm, a southward turning of the interplanetary magnetic field (IMF) B z component initiates a growth of substorm activity and a rapid increase of high-latitude convection electric field.…”

Section: Introductionmentioning

confidence: 99%

A Statistical Study on The Local Time Dependence of Equatorial Spread F (ESF) Irregularities and Their Relation to Low‐Latitude Es Layers Under Geomagnetic Storms

Singh

Sripathi

2020

JGR Space Physics

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In this paper, we present a study on the local time dependence of equatorial spread F (ESF) irregularities and their relation to low-latitude Es layers in response to geomagnetic storms using simultaneous observations of two ionosondes one located at Tirunelveli (8.73°N, 77.70°E), an equatorial station and other located at Hyderabad (17.36°N, 78.47°E), an off-equatorial station during the years 2007-2015 that covers solar cycles 23 and 24. The Aarons criteria for the ESF irregularities for different seasons under geomagnetic storms are evaluated. In the category I, we noticed partial enhancement in prereversal enhancement (PRE) during postsunset resulting in~30% occurrence of spread F instead of total inhibition during equinox and winter seasons. Also, occurrence of ESF in summer is suppressed by onlỹ 75% due to partial increase in PRE. In category II, we observed presunrise height enhancement mostly during winter, which caused ESF to occur at~50% followed by equinox and summer. The results presented here suggest that many are actually not following the Aarons criteria possibly due to not considering other background conditions. Accordingly, we examined the plausible role of low-latitude Es layers on the generation of ESF irregularities under these categories during geomagnetic storms. We noticed the absence/presence of Es layers in both categories during postsunset and postmidnight hours resulting in increase/decrease of PRE due to modifications in the field-line-integrated Pederson conductivity. Accordingly, the results suggest that one of the plausible reasons for ESF irregularities not following Aarons criteria is linked to the variability of the low-latitude Es layers. Plain Language SummaryThe electric fields and winds in the equatorial and low-latitude ionosphere are modified during geomagnetic storms due to coupling of solar wind-magnetosphereionosphere in the high latitudes. Accordingly, the occurrence of equatorial spread F (ESF) irregularities are significantly affected by the geomagnetic storms depending upon the time of the onset of the geomagnetic storm. We classified our observations into three categories based on Aarons criteria under different seasons to examine the role of geomagnetic storms on the generation/suppression of ESF irregularities based on the onset conditions of magnetic storms over India. The observations suggest that many ESF events could not follow this criterion due to not having included other background conditions. Accordingly, we examined the role of low-latitude Es layers, which may affect the field-integrated conductivities of the E and F regions during the onset times of ESF irregularities using larger data. The results suggest that whenever Es layers are present (absent) at low latitude, suppression (generation) of premidnight or postmidnight ESF irregularities at Tirunelveli is on rise. So these results suggest that if the low-latitude Es layers are taken into account, occurrence of ESF irregularities may be explained better by the above criteria.

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Global evolution of a substorm-associated DP2 current system observed by superDARN and magnetometers

Cited by 26 publications

References 4 publications

Equatorial counterelectrojets during substorms

Equatorial counterelectrojets during substorms

Low-latitude ionospheric-thermospheric response to storm time electrodynamical coupling between high and low latitudes

A Statistical Study on The Local Time Dependence of Equatorial Spread F (ESF) Irregularities and Their Relation to Low‐Latitude Es Layers Under Geomagnetic Storms

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