Global scale electrodynamic coupling of the auroral and equatorial dynamo regions

Reddy, C. A.; Somayajulu, V. V.; Devasia, C. V.

doi:10.1016/0021-9169(79)90012-6

Cited by 59 publications

(29 citation statements)

References 11 publications

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“…It is well known that many types of global-scale disturbance exhibit an enhancement at the EEJ latitudes (Onwumechilli and Ogbuehi, 1962;Akasofu and Chapman, 1963;Onwumechilli et al, 1973). Much data analysis has been performed which delineates the relationship between auroral magnetic ®eld and the equatorial variations in the magnetic ®eld, in foF2, in the occurrence of irregularities or the electric ®eld serving as the primary driver for the equatorial ionization anomaly or EEJ (Abdu et al, 1988;Fejer, 1986;Rastogi, 1973b;Reddy et al, 1979;Tanaka 1986;Tanaka and Ohtaka, 1996). This paper contributes further to this area of study.…”

Section: Introductionmentioning

confidence: 84%

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

Kobea

Amory‐Mazaudier²,

M.³

et al. 1998

Ann. Geophys.

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Abstract. Geomagnetic storm-time variations often occur coherently at high latitude and the day-side dip equator where they a ect the normal eastward Sq ®eld. This paper presents an analysis of ground magnetic ®eld and ionospheric electrodynamic data related to the geomagnetic storm which occured on 27 May 1993 during the International Equatorial Electrojet Year (IEEY) experiment. This storm-signature analysis on the auroral, mid-latitude and equatorial ground ®eld and ionospheric electrodynamic data leads to the identi®cat-ion of a sensitive response of the equatorial electrojet (EEJ) to large-scale auroral return current: this response consists in a change of the eastward electric ®eld during the pre-sunrise hours (0400±0600 UT) coherently to the high-, mid-, and equatorial-latitude H decrease and the disappearance of the EEJ irregularities between the timeinterval 0800±0950 UT. Subsequent to the change in h'F during pre-sunrise hours, the observed foF2 increase revealed an enhancement of the equatorial ionization anomaly (EIA) caused by the high-latitude penetrating electric ®eld. The strengthening of these irregularities attested by the Doppler frequency increase tracks the H component at the equator which undergoes a rapid increase around 0800 UT. The DH variations observed at the equator are the sum of the following components: S R , DP, DR, DCF and DT.

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Section: Introductionmentioning

confidence: 84%

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

Kobea

Amory‐Mazaudier²,

M.³

et al. 1998

Ann. Geophys.

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“…It is known that the midlatitude conductivity is low in comparison to the high and equatorial latitudes. Reddy et al [1978] have stated that the high latitude electric field perturbations penetrate to the equatorial latitudes with reduction factors of ∼10 in the longitude sector of the source region. Consequently, smaller electric field perturbations do not produce any significant surface magnetic field variations at midlatitudes.…”

Section: Resultsmentioning

confidence: 99%

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

et al. 2011

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“…Several researchers observed that the interplanetary electric field (IEF) could penetrate into the magnetosphere-ionosphere system (Reddy et al, 1979;Kelley et al, 1979). Some studies (Huang et al, 2005a, b;Mannucci et al, 2005;Tsurutani et al, 2004aTsurutani et al, , 2008a proposed a long-duration prompt penetration of IEF into ionosphere during large southward incursions of IMF B z and a large uplift of ionospheric plasma with a resulting enhanced TEC on the EIA crests.…”

Section: P M De Siqueira Negreti Et Al: Total Electron Content Resmentioning

confidence: 99%

Total electron content responses to HILDCAAs and geomagnetic storms over South America

2017

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Abstract. Total electron content (TEC) is extensively used to monitor the ionospheric behavior under geomagnetically quiet and disturbed conditions. This subject is of greatest importance for space weather applications. Under disturbed conditions the two main sources of electric fields, which are responsible for changes in the plasma drifts and for current perturbations, are the short-lived prompt penetration electric fields (PPEFs) and the longer-lasting ionospheric disturbance dynamo (DD) electric fields. Both mechanisms modulate the TEC around the globe and the equatorial ionization anomaly (EIA) at low latitudes. In this work we computed vertical absolute TEC over the low latitude of South America. The analysis was performed considering HILDCAA (high-intensity, long-duration, continuous auroral electrojet (AE) activity) events and geomagnetic storms. The characteristics of stormtime TEC and HILDCAA-associated TEC will be presented and discussed. For both case studies presented in this work (March and August 2013) the HILDCAA event follows a geomagnetic storm, and then a global scenario of geomagnetic disturbances will be discussed. Solar wind parameters, geomagnetic indices, O / N 2 ratios retrieved by GUVI instrument onboard the TIMED satellite and TEC observations will be analyzed and discussed. Data from the RBMC/IBGE (Brazil) and IGS GNSS networks were used to calculate TEC over South America. We show that a HILDCAA event may generate larger TEC differences compared to the TEC observed during the main phase of the precedent geomagnetic storm; thus, a HILDCAA event may be more effective for ionospheric response in comparison to moderate geomagnetic storms, considering the seasonal conditions. During the August HILDCAA event, TEC enhancements from ∼ 25 to 80 % (compared to quiet time) were observed. These enhancements are much higher than the quiet-time variability observed in the ionosphere. We show that ionosphere is quite sensitive to solar wind forcing and considering the events studied here, this was the most important source of ionospheric responses. Furthermore, the most important source of TEC changes were the long-lasting PPEFs observed on August 2013, during the HILDCAA event. The importance of this study relies on the peculiarity of the region analyzed characterized by high declination angle and ionospheric gradients which are responsible for creating a complex response during disturbed periods.

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Global scale electrodynamic coupling of the auroral and equatorial dynamo regions

Cited by 59 publications

References 11 publications

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

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

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

Total electron content responses to HILDCAAs and geomagnetic storms over South America

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