Isolated Substorm Driven Prompt Penetration Electric Field Signatures Over the Equatorial Ionosphere

This work presents the isolated substorm-driven strong eastward penetration electric field signatures over the Jicamarca (11.9°S, 76.8°W, magnetic dip 1°N) before midnight hours, at 22:00 LT (03:00 UT). This study used Jicamarca radar measurements to study the response of equatorial ionospheric electrodynamics and spread F irregularities. We also used Digisonde data for ionospheric virtual height (h’F) and equatorial spread F (ESF), Advanced Composition Explorer (ACE) satellite measurements for solar wind conditions, and SuperMAG geomagnetic field observations for geomagnetic field variations. Our analysis suggests that the significant disturbances in vertical (eastward electric field) and zonal (meridional electric field) plasma drifts noticed at Jicamarca are driven by isolated substorm. At 22:00 LT, the verticle and zonal plasma drifts increased to around 180 m/s and 625 m/s, respectively, and the h'F reached around 400 km. The analysis also shows that the height of ionospheric irregularities changes when vertical plasma drift changes. During the enhancements of verticle plasma drifts, interplanetary and geomagnetic conditions were quiet and steady, with values of ~-30 nT, 2.5 mV/m, and ~-4 nT for the Dst index, IEFy, and IMF Bz, respectively. However, auroral electrojets indicate the existence of substorm with AE (AU/AL) value of ~1710 (680/1036) nT. In addition, an increase in the equatorial electrojet (EEJ) calculated from the Jicamarca and Piura stations was observed, and the horizontal-H component of the magnetic field measured by the meridional chain of magnetometers showed a substorm effect.