Response of Thermospheric Nightglow Emissions Over the Magnetic Equator to Prompt Penetration Electric Field Events

Abstract

AbstractThis study examines the response of the nighttime thermosphere‐ionosphere system (TIS) over a dip equatorial station, Trivandrum (8.5°N, 77°E, 0.5° dip latitude) to prompt penetration electric field (PPEF) events occurred on 5 January 2016 and 6 March 2016. The investigation is based on nightglow emission measurements at wavelengths OI 777.4 nm, OI 630.0 nm, and OI 557.7 nm using a multiwavelength nighttime photometer. These emissions emanate from different altitude regions of the TIS, that is, 557.7 nm from ~100 km, 630.0 nm from ~220 km, and 777.4 nm from ~350 km. It has been observed that, during the westward PPEF event, the intensities of 777.4‐ and 630.0‐nm nightglow emissions enhance, whereas during the eastward PPEF event the intensities decrease. Similarly, though it is not very prominent, 557.7‐nm emission also exhibits a small enhancement/decrease during the westward/eastward PPEF events. The ionospheric base height obtained from a collocated digital ionosonde shows that during the eastward (westward) PPEF event the ionospheric layer moves upward (downward). The downward (upward) layer movement increases (decreases) the plasma density in the centroid of these airglow emissions, which in turn enhances (decreases) the emission rates. The study demonstrates the coupling between interplanetary medium and neutral TIS during nighttime PPEF events.