Estimation of downward heat flux into the F-region from the inner-magnetosphere during stable auroral red (SAR) arc events in the daytime obtained using OI 630.0 nm red-line emissions

Abstract

Stable Auroral Red (SAR) arcs are enhanced OI 630.0 nm emissions formed due to an increased electron temperature (Te) near the equatorward wall of mid-latitude trough during geomagnetic disturbances. The Te enhancement associated with SAR arcs is driven by electron heating through heat flux precipitation from near plasmapause region to ionospheric F-region via heat conduction. Although Te enhancements have been reported by radar/satellite measurements along with increased 630.0 nm brightness during SAR arc events, measurements of corresponding heat flux are sparse, and almost none in the daytime. This work presents the results on the estimation of electron heat flux incident during SAR arcs formed during daytime obtained by a comprehensive suite of measurements, and forward modeling. We present observations of several SAR arc events when the ground-based OI 630.0 nm emissions were larger than the model values during disturbed periods and were found to be existing in conjunction with increased Te at the altitude of DMSP (∼840 km). Forward modeling was carried out to determine the values of Te that would cause an enhancement in these emissions during daytime at much lower altitudes (∼400–500 km). These values of Te were used to estimate the required electron heat flux varying in the range of ∼1.0–4.6 × 1010 eV-cm−2-s−1. These results present the first estimates of F-region heat flux enabled using ground-based OI 630.0 nm emissions and open a new approach in the investigations of energy released into the ionosphere through heat conduction for daytime conditions during geomagnetically disturbed periods.