Ion temperatures measured by the retarding potential analyzer carried
aboard the Pioneer Venus Orbiter were sorted according to the ionosphe
ric magnetic field conditions. It was found that the dayside ion tempe
ratures measured during the first couple of years of operations, corre
sponding to solar maximum conditions and while the periapsis was held
at low altitudes (similar to 150 km), were basically independent of th
e magnetic conditions. This contrasts with earlier studies, which show
ed that electron temperatures are significantly elevated when the iono
sphere is magnetized. Theoretical studies by Cravens et al. [1980] pre
dicted that electron temperatures will depend on fluctuating magnetic
fields, but not the ion temperatures. This is consistent with these fi
ndings.