Determination of electron heat flux in the topside ionosphere and its impact on the vertical profile of OI 630.0 nm emission rate during nighttime SAR arcs for different solar activity conditions

Abstract

Electron heat flux in the ionosphere plays a crucial role in altering the electron temperature and thermal balance of the electron population, especially over subauroral- and high-latitudes. The downward flow of electron heat flux in the subauroral-latitude ionosphere through magnetosphere-ionosphere coupling causes an enhancement in the electron temperature, thereby leading to the formation of Stable Auroral Red (SAR) arcs. Understanding the relationship between heat flux and electron temperature is critical, as no technique exists to measure heat flux directly in the SAR arc region. This study primarily reports the characteristics of thermal electron heat flux of SAR arcs in the sub-auroral ionosphere and its influence on the plasma densities in the inner-magnetosphere and the SAR arc peak emission altitude. The downward electron heat flux has been characterized by using measured atomic oxygen red line emission intensity in conjunction with simultaneous enhancements of electron temperature by in-situ measurements for several nighttime SAR arc events reported in the literature for the period of 2012–2020 of solar cycle-24, and by using GLOW, a physics-based model. The present investigation reveals considerable variation in the estimated heat flux and SAR arc emission altitudes due to the influence of solar activity. This study, thus, quantifies the electron heat flux, averaging 2.89 × 1011 eV-cm−2-sec-1 near solar minimum and 8.05 × 1012 eV-cm−2-sec-1 during solar maximum, associated with ionospheric heating during observations of nighttime SAR arcs and their relevance to space weather phenomena.