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 degrees-360 degrees E) and Eurasia (0 degrees-160 degrees E) (Southern Oceania (80 degrees-280 degrees 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 similar to 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.