Equatorial Ionospheric Electric Fields During the November 2004 Magnetic Storm

Fejer, Bela G.; Jensen, Jesper Ole; Kikuchi, Takashi; Abdu, M. A.; Chau, Jorge L.

doi:10.1029/2007ja012376

Cited by 196 publications

(280 citation statements)

References 47 publications

Supporting

Mentioning

267

Contrasting

Order By: Relevance

“…It is shown that overshielding can occur in association with a decrease of the magnitude of the southward IMF (in this paper we also refer it to northward turning though the IMF does not become northward) . Moreover, the overshielding signatures are observed even under stable southward IMF [Fejer et al, 2007;Ebihara et al, 2008], implying that IMF northward turning is not a necessary condition for overshielding. What has become clear is that IMF northward turning is the most effective factor to cause overshielding, but some other factors, either outside or inside the magnetosphere-ionosphere system, can also contribute to the overshielding effect, such as a large drop of solar wind dynamic pressure [e.g., Wei et al, 2008b] and substorm processes [e.g., Ebihara et al, 2008;Wei et al, 2009;Zhang et al, 2009].…”

Section: Introductionmentioning

confidence: 89%

“…[33] The typical solar wind condition in which IMF suddenly turns northward after a prolonged southward orientation is neither a necessary condition [Fejer et al, 2007;Ebihara et al, 2008] nor a sufficient condition for overshielding. For the transition from goodshielding to overshielding, the overshielding effects immediately take place in association with a drop of the convection electric field, regardless of the shape of IMF northward turning.…”

Section: Discussionmentioning

confidence: 99%

“…[29] Fejer et al [2007] showed very large eastward and westward daytime electrojet current perturbations with lifetimes of about an hour (indicative of undershielding and overshielding prompt penetration electric fields) in the Pacific equatorial region during the 7 November main phase of the storm, when the southward IMF, the solar wind and reconnection electric fields, and the polar cap potential drops had very large and nearly steady values. Ebihara et al [2008] found an antisunward flow in the predusk sector subauroral region during a period of southward oriented IMF.…”

Section: Some Further Commentsmentioning

confidence: 99%

See 2 more Smart Citations

The transition to overshielding after sharp and gradual interplanetary magnetic field northward turning

Wei

Wan

et al. 2011

J. Geophys. Res.

View full text Add to dashboard Cite

[1] Overshielding is referred to a shielding status, during which the dawnward shielding electric field dominates over the duskward penetration electric field in the inner magnetosphere, typically appearing when the interplanetary magnetic field (IMF) suddenly turns northward after a prolonged southward orientation. It is expected that the transition to overshielding after IMF northward turning can be affected by the shape of northward turning (sharp or gradual). Moreover, the initial shielding status (undershielding or goodshielding) prior to the transition may also have influence on the transition. Here we analyze two groups of cases, in which the transitions appear after sharp (duration less than 5 min) and gradual (duration more than 30 min) northward turning. Each group includes two cases, in which the transition initiated from undershielding and goodshielding. These cases show that (1) the beginning of the transition to overshielding coincides with sharp IMF northward turning but appears in the midst of gradual IMF northward turning; (2) the transition from goodshielding to overshielding is always associated with convection electric field drop and/or polar cap shrinkage, regardless of the shape of IMF northward turning; and (3) the typical solar wind condition in which the IMF suddenly turns northward after a prolonged southward orientation is neither a necessary condition nor a sufficient condition for overshielding. Furthermore, we will discuss the effect of substorm processes on overshielding.

show abstract

Section: Introductionmentioning

confidence: 89%

Section: Discussionmentioning

confidence: 99%

Section: Some Further Commentsmentioning

confidence: 99%

See 1 more Smart Citation

The transition to overshielding after sharp and gradual interplanetary magnetic field northward turning

Wei

Wan

et al. 2011

J. Geophys. Res.

View full text Add to dashboard Cite

show abstract

“…Several workers have investigated the storm event of November 8-10, 2004, which is discussed in this paper (Balan et al, 2008a;Dabas et al, 2006;Fejer et al, 2007;Dashora and Pandey, 2007;Astafyeva, 2009). In these papers, the effects of storm-time electric fields in modulating ionization distribution is stressed.…”

Section: Discussionmentioning

confidence: 99%

“…They observed a sharp enhancement in f o F 2 values during the forenoon hours on November 8, 2004, and a sharp rise in h F around the period of Dst maximum negative excursion during nighttime on November 9-10, 2004. Fejer et al (2007) studied the electric fields over equatorial ionosphere during the November 7-9, 2004, geomagnetic storm, using radar measurements from the Jicamarca Radio Observatory, magnetometer observations from the Pacific sector and ionosonde data from Brazil. They showed very large eastward and westward daytime electrojet current perturbations with lifetimes of about an hour (indicative of undershielding and overshielding prompt penetration electric fields) in the Pacific equatorial region during November 7, which was the main phase of the storm.…”

Section: Introductionmentioning

confidence: 99%

Ionospheric response to a geomagnetic storm during November 8–10, 2004

et al. 2013

View full text Add to dashboard Cite

This paper investigates the response of the equatorial, and near equatorial, ionosphere to geomagnetic disturbances during the period November [8][9][10] 2004. Ionosonde data from Trivandrum (8.5• N 77• E and dip 0.5• N) and SHAR (13.5 • N, 80.2 • E, dip ∼5.5• N), magnetic field data from Tirunelveli (8.7• N, 76.9• E, dip latitude 0.5 • S) and Alibag (18.64 • N, 72.87• E), and GUVI O/N 2 data in the Indian longitude sector, are used for the study. The behavior of interplanetary parameters is also examined in conjunction with the ionospheric data. On 8 November, the EIA around noontime is not fully inhibited even though the electrojet strength an indicates inhibition of EIA due to a disturbance dynamo electric field effect. It is the enhanced O/N 2 over TRV and SHAR, with a larger increase over SHAR, which results in a larger (than expected) value of the EIA proxy parameter. On 9 November, the comparable values of f o F 2 at TRV and SHAR around noon time is due to the combined effect of a weakened anomaly in the presence disturbance dynamo electric field effects leading to the EIA crest being near SHAR, and increased O/N 2 values at TRV and SHAR with a larger increase at TRV. On 10 November, the very strong values of the EIA proxy-SHAR parameter is attributed to the combined effects of prompt penetration electric field related modulations of EIA, and significant O/N 2 changes at the equatorial, and near equatorial, latitude. Thus, the study reveals the important role of storm-induced O/N 2 changes, along with prompt penetration electric fields and disturbance dynamo electric fields in modulating the ionization distribution in the equatorial ionization anomaly (EIA) region during this period.

show abstract

Equatorial westward electrojet impacting equatorial ionization anomaly development during the 6 April 2000 superstorm

Horvath

Lovell

2013

JGR Space Physics

View full text Add to dashboard Cite

[1] We investigate the forward plasma fountain and the equatorial ionosphere in the topside region during the 6 April 2000 superstorm in the Australian sector at~0900 LT. Space-and ground-based multi-instrument measurements, Coupled Thermosphere-IonospherePlasmasphere Electrodynamics (CTIPe) simulations, and field-aligned observations comprise our results. These reveal an unusual storm development during which the eastward prompt penetration electric (E) field (PPEF) developed and operated under the continuous effects of the westward disturbance dynamo E-field (DDEF) while large-scale traveling ionospheric disturbances (TIDs) traveled equatorward and generated strong equatorward wind surges. We have identified the eastward PPEF by the superfountain effect causing the equatorial ionization anomaly (EIA)'s development with crests situated at~±28°N (geomagnetic) in the topside ionosphere at~840 km altitude. The westward DDEF's occurrence is confirmed by mapping the "anti-Sq" current system wherein the equatorial westward current created a weak long-lasting westward electrojet event. Line plots of vertical drift data tracked large-scale TIDs. Four scenarios, covering~3.5 h in universal time, demonstrate that the westward DDEF became superimposed on the eastward PPEF. As these E-fields of different origins became mapped into the F region, they could interact. Consequently, the eastward PPEF-related equatorial upward E Â B drift became locally reduced by up to 75 m/s near the dip equator by the westward DDEF-related equatorial downward E Â B drift. Meanwhile, the EIA displayed a better development as equatorial wind surges, reproduced by CTIPe, increased from 501 to 629 m/s, demonstrating the crucial role of mechanical wind effects keeping plasma density high.

show abstract

Equatorial Ionospheric Electric Fields During the November 2004 Magnetic Storm

Cited by 196 publications

References 47 publications

The transition to overshielding after sharp and gradual interplanetary magnetic field northward turning

The transition to overshielding after sharp and gradual interplanetary magnetic field northward turning

Ionospheric response to a geomagnetic storm during November 8–10, 2004

Equatorial westward electrojet impacting equatorial ionization anomaly development during the 6 April 2000 superstorm

Contact Info

Product

Resources

About