Global energy deposition to the topside ionosphere from superthermal electrons

The subauroral heat input to the topside ionosphere from two superthermal electron sources, photoelectrons and plasma sheet electrons, are calculated using a global kinetic model of electron transport in the inner magnetosphere. Peak rates above 10¹⁰ eV cm^-2 s^-1 are found for photoelectrons in the midlatitude afternoon region, while the peak deposition rate for plasma sheet electrons only occasionally approaches 10⁹ eV cm^-2 s^-1, and is typically confined to the morningside. Trapped clouds of plasma sheet electrons, however, are shown to have lasting effects on the structure of topside heat input, as the energetic electrons corotate and slowly transfer their energy to the thermal plasma over a course of days. These energy inputs are compared with other heat sources in the inner magnetosphere. It is concluded that, while other processes can inject large amounts of energy into the ionosphere in spatially and temporally localized regions, photoelectrons are the strongest and steadiest heat source into the topside ionosphere.