Effect of Disturbance Electric Fields on Equatorial Electrojet Over Indian Longitudes

Abstract

Prompt penetration (PP) and ionospheric disturbance dynamo (Ddyn) are two expressions of the disturbed electric field developed during a geomagnetic storm in the Earth's ionosphere. Earlier investigations treated these two processes independently over longitudinal separation beyond 20°. In the present study, we investigate the conjunction of these phenomena on equatorial electrojet at 20° longitude separations using daytime magnetic field data from three equatorial sites viz., Minicoy, Vencode, and Campbell Bay and three low‐latitude sites viz., Alibag, Hyderabad, and Nabagram, located within 20° longitude over Indian region, during three intense storms (Dst <− 150 nT). We propose a statistical method to identify PP signatures from large data set. In addition, we distinguish the signatures of PP and Ddyn during early recovery phase of intense storms and compute pure Ddyn signature in the late recovery phase. It is seen that the effect of PP is similar at the three equatorial sites for each storm. We find that signatures of Ddyn are amplified at Minicoy and Vencode compared to Campbell Bay, and their magnitude decreases toward low‐latitude stations, also reflected in the current vector patterns. Our investigations of intense geomagnetic storms show that PP effect dominates the main phase, followed by a combined effect of PP and Ddyn in the early recovery phase. Eventually the Ddyn signature dominates in the late recovery phase with decreasing amplitudes of Ddyn with increasing time. Such investigations can provide new information about variations in ionospheric parameters.

Constraints on Scale Lengths of Equatorial Electrojet and Counter Electrojet Phenomena From the Indian Sector

“…The variability demonstrated at 5° separations in our study is direct evidence of the influence of short scale length processes. The other significant finding from our study is for the westward increase in CEJ amplitude and occurrence that have been attributed to wave‐tide interaction. We have shown that the same trend is evident for both quiet and disturbed periods indicating the pervasive influence of DE3 tide corroborated by Bulusu et al () and Singh et al ().…”

“…This provides strong evidence of the influence of DE3 tidal forcing on the effectiveness of the localized perturbations; MNC (72°E) is closer to the DE3 trough at 60°E, and CBY (93°E) is closer to the crest at 100°E. This trend of increasing westward CEJ amplitude, even during disturbed periods, indicates the control of DE3 over westward currents (disturbed dynamo and prompt penetration signatures) generated by magnetospheric disturbances, corroborating findings of Bulusu et al (). The decreasing CEJ amplitudes eastward are corroborated by the recent study of quiet time CEJ occurrences in CHAMP data (Singh et al, ).…”

Spatial Variations in Disturbance Ionospheric Currents—Inference From 12 Geomagnetic Storms

“…Zaka et al (2009) have demonstrated formation of anti‐Sq current patterns associated with a geomagnetic storm across the globe. Recent examples of investigations of PP, Ddyn, and their combined effect have been discussed in Bulusu et al (2018) and references therein. The first investigation of PP and Ddyn occurrences along different longitudes in the Indian sector was performed by Bulusu et al (2018) for three intense geomagnetic storms of 2015.…”

“…Recent examples of investigations of PP, Ddyn, and their combined effect have been discussed in Bulusu et al (2018) and references therein. The first investigation of PP and Ddyn occurrences along different longitudes in the Indian sector was performed by Bulusu et al (2018) for three intense geomagnetic storms of 2015. The investigation discussed the signatures of PP and Ddyn in small longitude sectors (<20°).…”

“…In the present investigation, we work on the same three longitude sectors as in Bulusu et al (2018), incorporating more stations from low and middle latitudes to establish the latitudinal as well as longitudinal pattern of disturbance ionospheric currents during geomagnetic storms. We confine our study to geomagnetic storms with Dst ranging between −50 and −130 nT that lasted for three to 4 days.…”