The equatorial electrojet and the day-to-day variability of Sq

Mann, Robert James; Schlapp, D. M.

doi:10.1016/0021-9169(88)90009-8

Cited by 19 publications

(14 citation statements)

References 13 publications

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“…The ionospheric current system in Figure b gives an explanation for a poor correlation between S q ( H ) at the magnetic equator and off the magnetic equator that has been reported by previous researchers [e.g., Kane , ; Mann and Schlapp , ]. Our simulation results showed that the correlation coefficient between the daily range of S q ( H ) at the magnetic equator and other latitudes of the same longitude decreases to below 0.5 for a latitudinal separation of 10° (not shown).…”

Section: Resultssupporting

confidence: 50%

On the day‐to‐day variation of the equatorial electrojet during quiet periods

et al. 2014

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It has been known for a long time that the equatorial electrojet varies from day to day even when solar and geomagnetic activities are very low. The quiet time day‐to‐day variation is considered to be due to irregular variability of the neutral wind, but little is known about how variable winds drive the electrojet variability. We employ a numerical model introduced by Liu et al. (2013), which takes into account weather changes in the lower atmosphere and thus can reproduce ionospheric variability due to forcing from below. The simulation is run for May and June 2009. Constant solar and magnetospheric energy inputs are used so that day‐to‐day changes will arise only from lower atmospheric forcing. The simulated electrojet current shows day‐to‐day variability of ±25%, which produces day‐to‐day variations in ground level geomagnetic perturbations near the magnetic equator. The current system associated with the day‐to‐day variation of the equatorial electrojet is traced based on a covariance analysis. The current pattern reveals return flow at both sides of the electrojet, in agreement with those inferred from ground‐based magnetometer data in previous studies. The day‐to‐day variation in the electrojet current is compared with those in the neutral wind at various altitudes, latitudes, and longitudes. It is found that the electrojet variability is dominated by the zonal wind at 100–120 km altitudes near the magnetic equator. These results suggest that the response of the zonal polarization electric field to variable zonal winds is the main source of the day‐to‐day variation of the equatorial electrojet during quiet periods.

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Section: Resultssupporting

confidence: 50%

On the day‐to‐day variation of the equatorial electrojet during quiet periods

et al. 2014

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“…For BDV, there is no consistency in the degree of correlation and the random nature (both positive and negative inter-relationships or no relationship) is independent of solar activity. Mann and Schlapp (1988), from a detailed study of the day-to-day variability in the quiet day range of horizontal intensity, concluded that the stations under the equatorial electrojet are significantly less well correlated than non-electrojet station pairs. Our results are not immediately comparable with Mann and Schlapp but in general they are in agreement.…”

Section: Resultsmentioning

confidence: 99%

“…The bandpass-filtered data for consecutive eight days overlapped by 4 days are then analysed by Maximum Entropy Method (Marple, 1987). It is well known that MEM does not yield accurate estimates of amplitude while the frequency is well determined.…”

Section: Discussionmentioning

confidence: 99%

Quasi-Bidaily Variation of the Geomagnetic Field in the Indian Equatorial Zone.

Rangarajan

1994

J. geomagn. geoelec

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Quasi-bidaily Variation (BDV) in the geomagnetic field due to equatorial electrojet and planetary Sq currents is clearly detected in the Indian equatorial zone. The quasi-stationary signal is stronger in EEJ compared to SQ. Larger amplitude of the BDV in EEJ is confined only to late summer in the northern hemisphere indicative of its clear association with the planetary wave in the mesosphere below. A noticeable change in the BDV amplitude is seen following counter electrojet events. However, no concrete evidence is seen for the anticipated association between the movement of Sq focus caused by mesospheric winds and the BDV in EEJ or Sq.

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“…In many cases, poor correlation was found (Osborne 1963(Osborne , 1966(Osborne , 1968Ogbuehi et al 1967;Schlapp 1968;Mann and Schlapp 1988;Manoj et al 2006;Abdul Hamid et al 2014). The results were often taken as evidence that the equatorial electrojet is not a simple enhancement of Sq currents and hence other driving mechanisms exist for the EEJ.…”

Section: Sq-eej Relationshipmentioning

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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The equatorial electrojet and the day-to-day variability of Sq

Cited by 19 publications

References 13 publications

On the day‐to‐day variation of the equatorial electrojet during quiet periods

On the day‐to‐day variation of the equatorial electrojet during quiet periods

Quasi-Bidaily Variation of the Geomagnetic Field in the Indian Equatorial Zone.

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

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