Electron temperature (Te) in the topside ionosphere and plasmasphere
is an important parameter because thermal electrons play a key role in
the energy balance of these regions. The IRI (International Reference
ionosphere) model includes an empirical representation of Te in the
topside ionosphere depending on altitude, latitude, local time, and
season. But due to a lack of data and sometimes conflicting
measurements, the solar activity variation of Te has not been reliably
modeled so far.

We have made good progress in modeling the Te behavior with the help
of a large database of satellite electron temperature measurements,
and of Incoherent Scatter Radars observations, and with the assistance
of simulations with the theoretical FLIP model. The presentation will
focus in particular on (1) comparison of calculation of the FLIP model
with data (2) latitudinal and altitudinal variation of Te and the heat
flux (3) discussion prevailing cooling and heating terms influencing
Te balance and causing its changing with solar activity. We will also
discuss development of a new global Te model with the Te solar
activity variation as a correction term which can help to improve
current Te model in IRI.