Global Distribution of Electron Temperature Enhancement at Mid‐Low Latitudes Observed by DMSP F16 Satellite.

This study investigates the global distribution of electron temperature enhancement observed by Defense Meteorological Satellite Program F16 satellite and its dependence on the season and solar activity for the solar maximum (2014) and minimum (2018) years during geomagnetic quiet times (maximum per day ap <10). Electron temperature enhancements occurred mainly over the North American‐Atlantic (260°–360°E) and Eurasia (0°–160°E) (Southern Oceania (80°–280°E)) sector in the Northern (Southern) Hemisphere and are prominent in the winter hemispheres and solar maximum year. They have obvious longitude characteristics. Interestingly, they could extend to geomagnetic equatorial regions in the North American‐Atlantic sector from high to low latitudes in the December Solstice, further crossed the magnetic equator, and merged into the Southern Hemisphere in 2014, where the maximum temperature reached ∼3500 K. Our analysis indicates that low‐energy electrons (<100 eV) associated with photoelectron from the conjugate sunlit hemisphere, can contribute to these enhancements. Furthermore, the local geomagnetic declination, magnetic equator position, and terminator position at magnetic conjugate points together can impact the global distribution of photoelectrons of different energies and therefore the electron temperature enhancement distribution. Other processes (including local electron density variation) may play certain roles as well. Plain Language Summary: Photoelectrons are supra‐thermal low‐energy electrons in the sunlit hemisphere that can move to the nightside hemisphere along the magnetic field lines and heat the thermal electrons around the conjugate location, which causes the electron temperature anomalous enhancement and re‐distribution of electron temperature at mid‐low latitudes on nightside. The global distribution characteristics, seasonality, and solar activity of the electron temperature enhancement were studied using in‐situ DMSP F16 satellite plasma, energy particle precipitation, and geomagnetic field observations in 2014 and 2018 during geomagnetic quiet times. It is shown that the electron temperature enhancement is prominent in the Northern Atlantic (260°–360°E) (the Southern Oceania (80°–280°E)) sector in the Northern (Southern) Hemisphere winter and is more visible during a solar maximum year. Furthermore, the geomagnetic field configuration and the solar terminator around the two magnetic conjugate points modulate the photoelectron precipitated positions in the conjugate night hemisphere, and the magnetic field line length and intensity between the two magnetic conjugate points may determine the flux of the photoelectron precipitation, which all affect the global distribution of the electron temperature enhancement. Other factors, including electron density, which controls the cooling of electrons, could also impact the electron temperature under certain conditions. Key Points: Electron temperature enhancement occurs at night and is prominent in the 260°–360°E (80°–280°E) longitude region in the NH (SH) winterLow‐energy electrons (<100 eV) associated conjugate photoelectron and local electron density variation can contribute to the enhancementIts global distribution is determined by the geomagnetic field configuration and terminator around the two magnetic conjugate points [ABSTRACT FROM AUTHOR]