Equatorial electric fields during magnetically disturbed conditions 1. The effect of the interplanetary magnetic field

Fejer, Bela G.; Gonzales, C. A.; Farley, D. T.; Kelley, M. C.; Woodman, R. F.

doi:10.1029/ja084ia10p05797

Cited by 225 publications

(185 citation statements)

References 30 publications

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“…Early observations of zonal and vertical plasma flow at low latitudes were largely limited to those provided by ground-based techniques such as the Jicamarca incoherent scatter radar in Peru (e.g., Woodman, 1972;Fejer et al, 1979aFejer et al, , b, 1981Fejer et al, , 1985Fejer et al, , 1991. Such measurements provide comprehensive coverage with respect to local time, seasonal, and solar activity dependences at one geographic location.…”

Section: Introductionmentioning

confidence: 99%

Topside equatorial zonal ion velocities measured by C/NOFS during rising solar activity

et al. 2014

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Abstract. The Ion Velocity Meter (IVM), a part of the Coupled Ion Neutral Dynamic Investigation (CINDI) instrument package on the Communication/Navigation Outage Forecast System (C/NOFS) spacecraft, has made over 5 yr of in situ measurements of plasma temperatures, composition, densities, and velocities in the 400-850 km altitude range of the equatorial ionosphere. These measured ion velocities are then transformed into a coordinate system with components parallel and perpendicular to the geomagnetic field allowing us to examine the zonal (horizontal and perpendicular to the geomagnetic field) component of plasma motion over the 2009-2012 interval. The general pattern of local time variation of the equatorial zonal ion velocity is well established as westward during the day and eastward during the night, with the larger nighttime velocities leading to a net ionospheric superrotation. Since the C/NOFS launch in April 2008, F10.7 cm radio fluxes have gradually increased from around 70 sfu to levels in the 130-150 sfu range. The comprehensive coverage of C/NOFS over the low-latitude ionosphere allows us to examine variations of the topside zonal ion velocity over a wide level of solar activity as well as the dependence of the zonal velocity on apex altitude (magnetic latitude), longitude, and solar local time. It was found that the zonal ion drifts show longitude dependence with the largest net eastward values in the American sector. The pre-midnight zonal drifts show definite solar activity (F10.7) dependence. The daytime drifts have a lower dependence on F10.7. The apex altitude (magnetic latitude) variations indicate a more westerly flow at higher altitudes. There is often a net topside subrotation at low F10.7 levels, perhaps indicative of a suppressed F region dynamo due to low field line-integrated conductivity and a low F region altitude at solar minimum.

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Section: Introductionmentioning

confidence: 99%

Topside equatorial zonal ion velocities measured by C/NOFS during rising solar activity

et al. 2014

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“…Major geomagnetic storms are triggered by the earth directed coronal mass ejections (CMEs) from the sun when under the condition of a southward interplanetary magnetic field (IMF B z ), interaction between the solar wind and magnetosphere causes under shielding conditions and produces electric fields at the magnetospheric heights that may penetrate up to the equatorial latitudes. These fields are termed prompt penetration electric fields, PPEF (Nishida et al, 1966;Fejer et al, 1979;Fejer, 2002), which are eastward (westward) during the daytime (nighttime). It is generally believed that the PPEFs have rise and decay time of about 10-30 min, and are short lived and may last for an hour or so (Gonzalez et al, 1979;Senior and Blanc, 1984;Spiro et al, 1988;Fejer et al, 1990;Fejer and Scherliess, 1997;Fejer et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Longitudinal study of the ionospheric response to the geomagnetic storm of 15 May 2005 and manifestation of TADs

Sharma¹,

Galav²,

Dashora

et al. 2011

Ann. Geophys.

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Abstract.Response of low latitude ionosphere to the geomagnetic storm of 15 May 2005 has been studied using total electron content (TEC) data, obtained from three GPS stations namely, Yibal, Udaipur and Kunming situated near the northern crest of equatorial ionization anomaly at different longitudes. Solar wind parameters, north-south component of the interplanetary magnetic field (IMF B z ) and AE index data have been used to infer the strength of the geomagnetic storm. A large value of eastward interplanetary electric field at 06:15 UT, during the time of maximum southward IMF B z has been used to infer the transmission of an eastward prompt penetration electric field (PPEF) which resulted in a peak in TEC at 07:45 UT due to the local uplift of plasma in the low latitudes near the anomaly crest over a wide range of longitudes. Wave-like modulations superposed over the second enhancement in TEC between 09:15 UT to 10:30 UT have been observed at all the three stations. The second enhancement in TEC along with the modulations of up to 5 TECU have been attributed to the combined effect of super plasma fountain and traveling atmospheric disturbances (TAD). Observed large enhancements in TEC are a cause of concern for satellite based navigation and ground positioning. Increased [O/N 2 ] ratio between 09:15 UT to 10:15 UT when modulations in TEC have been also observed, confirms the presence of TADs over a wide range of longitudes.

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“…However, the equatorial ionosphere has been assumed to have a special advantage due to its being free from the FAC which occur in the polar ionosphere. As has been shown by Pudovkin et al (1975), Rastogi and Patel (1975), Fejer et al (1979), and Zakharov et al (1989), the equatorial ionosphere is controlled by the magnetospheric and interplanetary magnetic fields. These authors presumed that the short-term equatorial ionospheric variations could be explained by the action of the auroral sources.…”

Section: Discussionmentioning

confidence: 67%

Role of the magnetospheric and ionospheric currents in the generation of the equatorial scintillations during geomagnetic storms

Biktash

2004

Ann. Geophys.

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Abstract. The equatorial ionosphere parameters, K p , D st , AU and AL indices characterized contribution of different magnetospheric and ionospheric currents to the Hcomponent of geomagnetic field are examined to test the geomagnetic activity effect on the generation of ionospheric irregularities producing VLF scintillations. According to the results of the current statistical studies, one can predict near 70% of scintillations from Aarons' criteria using the D st index, which mainly depicts the magnetospheric ring current field. To amplify Aarons' criteria or to propose new criteria for predicting scintillation characteristics is the question. In the present phase of the experimental investigations of electron density irregularities in the ionosphere new ways are opened up because observations in the interaction between the solar wind -magnetosphere -ionosphere during magnetic storms have progressed greatly. According to present view, the intensity of the electric fields and currents at the polar regions, as well as the magnetospheric ring current intensity, are strongly dependent on the variations of the interplanetary magnetic field. The magnetospheric ring current cannot directly penetrate the equatorial ionosphere and because of this difficulties emerge in explaining its relation to scintillation activity. On the other hand, the equatorial scintillations can be observed in the absence of the magnetospheric ring current. It is shown that in addition to Aarons' criteria for the prediction of the ionospheric scintillations, models can be used to explain the relationship between the equatorial ionospheric parameters, h F , f oF 2, and the equatorial geomagnetic variations with the polar ionosphere currents and the solar wind.

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Equatorial electric fields during magnetically disturbed conditions 1. The effect of the interplanetary magnetic field

Cited by 225 publications

References 30 publications

Topside equatorial zonal ion velocities measured by C/NOFS during rising solar activity

Topside equatorial zonal ion velocities measured by C/NOFS during rising solar activity

Longitudinal study of the ionospheric response to the geomagnetic storm of 15 May 2005 and manifestation of TADs

Role of the magnetospheric and ionospheric currents in the generation of the equatorial scintillations during geomagnetic storms

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