Observational evidence for the plausible linkage of Equatorial Electrojet (EEJ) electric field variations with the post sunset F-region electrodynamics

Sreeja, V.; Devasia, C. V.; Ravindran, Sudha; Pant, Tarun Kumar

doi:10.5194/angeo-27-4229-2009

Cited by 23 publications

(27 citation statements)

References 43 publications

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“…It was suggested that day's EEJ strength might be a very useful parameter for prediction of equatorial plasma bubbles and associated irregularities. The positive contributions of daytime EEJ parameters to the postsunset F region electrodynamics favorable for generation of irregularities are also supported by recent studies [ Sreeja et al , 2009; Uemoto et al , 2010]. Present paper deals with some case studies involving ESF and scintillation events in the context of variation of EEJ.…”

Section: Introductionsupporting

confidence: 65%

Evolution of equatorial irregularities under varying electrodynamical conditions: A multitechnique case study from Indian longitude zone

Hajra¹,

Chakraborty²,

Mazumdar³

et al. 2012

J. Geophys. Res.

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[1] A comprehensive multitechnique study on the postsunset evolutions of equatorial ionization anomaly (EIA) and equatorial plasma density irregularities in the context of the varying electrodynamical conditions under normal equatorial electrojet (EEJ), complete and partial counter electrojet (CEJ) events is presented from the Indian longitude zone. The study involves analysis of scintillation data at VHF (250 MHz) and GPS L1 (1575.42 MHz) frequency, ionosonde data, magnetometer data along with global ionospheric maps (GIMs) of total electron content (TEC) for the vernal equinoctial months (March-April) of 2011. The investigation reveals inefficiency of the noontime peak EEJ to dictate the day-to-day variability of postsunset irregularity phenomena. Intensification of EEJ after $1530 IST (Indian standard time) on normal EEJ days and significantly enhanced residual fields presumably due to CEJ event after $1700 IST on complete and partial CEJ days are found to be associated with the resurgence of EIA and evolution of postsunset irregularities. The results are discussed in terms of superposition effects of electric fields arising from E-and F-region dynamos.

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Section: Introductionsupporting

confidence: 65%

Evolution of equatorial irregularities under varying electrodynamical conditions: A multitechnique case study from Indian longitude zone

Hajra¹,

Chakraborty²,

Mazumdar³

et al. 2012

J. Geophys. Res.

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“…The strong eastward equatorial electric field during the pre-reversal enhancement is linked to another phenomena called equatorial spread-F or plasma bubble, which is characterized by a depletion of the equatorial ionospheric plasma density (e.g., Burke et al 2004;Stolle et al 2006). Attempts have been made by several authors (e.g., Sreeja et al 2009;Uemoto et al 2010;Hajra et al 2012) to find a link between geomagnetic daily variations and the occurrence of the equatorial spread-F. For example, Uemoto et al (2010) reported that the occurrence of the equatorial spread-F is reduced when the equatorial electrojet 1-2 hours prior to the sunset is westward. Their results suggest the possibility of the detection of the equatorial spread-F using ground magnetometer data.…”

Section: Eej Intensity and Equatorial F-region Parametersmentioning

confidence: 99%

Sq and EEJ—A Review on the Daily Variation of the Geomagnetic Field Caused by Ionospheric Dynamo Currents

2016

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A record of the geomagnetic field on the ground sometimes shows smooth daily variations on the order of a few tens of nano teslas. These daily variations, commonly known as Sq, are caused by electric currents of several μA/m 2 flowing on the sunlit side of the Eregion ionosphere at about 90-150 km heights. We review advances in our understanding of the geomagnetic daily variation and its source ionospheric currents during the past 75 years. Observations and existing theories are first outlined as background knowledge for the nonspecialist. Data analysis methods, such as spherical harmonic analysis, are then described in detail. Various aspects of the geomagnetic daily variation are discussed and interpreted using these results. Finally, remaining issues are highlighted to provide possible directions for future work.

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“…This is a phenomenon that was measured with an enhancement of vertical drift at sunset and the activation of F region dynamo in the evening hour [Martinis et al, 2005;Sreeja et al, 2009;Adebesin et al, 2013a]. The vertical drift increases, reached a maximum peak at the start of eclipse, and decreases downward through the eclipse window close to zero drift thereafter.…”

Section: 1002/2015ja021557mentioning

confidence: 99%

Ionospheric vertical plasma drift and electron density response during total solar eclipses at equatorial/low latitude

2015

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The response of the vertical plasma drift (Vz) and the electron density (NmF2) during different solar eclipses was investigated. The diurnal values of the direct scaled measurement of F2 peak height and the one derived from M(3000) F2 data, acquired over an equatorial/low‐latitude stations, have been used to determine the vertical plasma drift. The ionosphere during a solar eclipse is significantly affected by the E × B vertical drift; the large depletion of electron density at low altitudes can be transported to high altitudes through the plasma vertical drift. The loss in ionization density during the eclipse phase decreases the electron density, which was accompanied by rapid increase in hmF2. This deviation in the NmF2 during eclipse compared to control days can be related to the increase in the loss rate due to recombination, as a result of reduction in thermal energy. However, the maximum reduction in NmF2 is not synchronous with the time of maximum totality but some minutes later. The differences in the solar epochs may contribute to the observed relative changes in the ionospheric F2 region behavior during the eclipse window. Lastly, it is very difficult to separate the influence of magnetic disturbances from solar eclipse. The deviation in NmF2 is higher during magnetic disturbed days than the quiet day. The reverse is the case for hmF2 observation. However, the NmF2 variation increases with an increase in solar activity.

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Observational evidence for the plausible linkage of Equatorial Electrojet (EEJ) electric field variations with the post sunset F-region electrodynamics

Cited by 23 publications

References 43 publications

Evolution of equatorial irregularities under varying electrodynamical conditions: A multitechnique case study from Indian longitude zone

Evolution of equatorial irregularities under varying electrodynamical conditions: A multitechnique case study from Indian longitude zone

Sq and EEJ—A Review on the Daily Variation of the Geomagnetic Field Caused by Ionospheric Dynamo Currents

Ionospheric vertical plasma drift and electron density response during total solar eclipses at equatorial/low latitude

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