Effect of disturbance electric fields on Equatorial Electrojet over Indian longitudes

Jayashree Bulusu, Archana R. K., Kusumita Arora, N. Phani Chandrasekhar and Nandini Nagarajan

Geomagnetic storms produce disturbance electric field in the ionosphere which restructures the ionospheric current patterns even after the storm is over. Prompt penetration (PP) and ionospheric disturbance dynamo (Ddyn) are two expressions of this disturbed electric field. In this study, we investigated the conjunction of these phenomena on equatorial electrojet at 20 degree longitude separations using daytime magnetic field data from three equatorial sites viz., Minicoy, Vencode, and Cambell Bay and three low-latitude sites viz., Alibag, Hyderabad, and Nabhagram, located within 20 degree longitude over Indian region, during three intense storms (Dst < −150 nT). We proposed a statistical method to identify PP signatures from large data set. In addition, we distinguished the signatures of PP and Ddyn during early recovery phase of intense storms and compute pure Ddyn signature in the late recovery phase. It was seen that the effect of PP is similar at the three equatorial sites for each storm whereas the signature of Ddyn was amplified at Minicoy and Vencode compared to Cambell Bay, and their magnitude decreased toward low-latitude stations, also reflected in the current vector patterns. Our investigations of intense geomagnetic storms showed 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 bring out the smaller scale lengths of disturbance electric field that can provide new information about variations in ionospheric parameters during  a geomagnetic storm.

Citation: Bulusu, J., R. K., A., Arora, K. ,Chandrasekhar, N. P., & Nagarajan, N (2018). Effect of disturbanceelectric fields on equatorial electrojet over Indian longitudes. Journal of Geophysical Research Space Physics, 123.



Figure 1: Disturbance electric field and inherent current patterns generated at equatorial and low latitude stations on 24 and 25 March 2015 after St.Patrick’s stormof 2015