Under current solar minimum conditions at Arecibo, Puerto Rico, large (~1000--2000 K) enhancements in electron temperature are observed in the winter, nighttime ionosphere when high-power 3-MHz radio waves reflect near the F region peak. Computational modeling has been performed to determine the cause of the unusually large temperature combined with strong thermal conduction along geomagnetic field lines play a key role in elevating F region temperatures and spreading the electron temperature enhancements far outside of the region where radio wave energy is deposited. Thus, the dramatically large temperature enhancements are attributable primarily to expected low cooling rates of the electron gas, rather than unexpectedly high heating rates. ¿ American Geophysical Union 1988