Global energy deposition to the topside ionosphere from superthermal electrons

The subauroral heat input to the topside ionosphere from two superthermal e lectron sources, photoelectrons and plasma sheet electrons, are calculated using a global kinetic model of electron transport in the inner magnetosphe re. Peak rates above 10(10) eV cm(-2) s(-1) are found for photoelectrons in the midlatitude afternoon region, while the peak deposition rate for plasm a sheet electrons only occasionally approaches 10(9) eV cm(-2) s(-1), and i s typically confined to the morningside. Trapped clouds of plasma sheet ele ctrons, however, are shown to have lasting effects on the structure of tops ide heat input, as the energetic electrons corotate and slowly transfer the ir 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 conc luded that, while other processes can inject large amounts of energy into t he ionosphere in spatially and temporally localized regions, photoelectrons are the strongest and steadiest heat source into the topside ionosphere. ( C) 2000 Elsevier Science Ltd. All rights reserved.