I have tried without luck to find a graph of temperature change through the atmosphere that goes further up than about 100 km. On this graph:
(Source: http://www.windows2universe.org/kids_space/temp_profile.html)
as on many others the temperature rises and rises and continues like that out of the scale. How will the temperature curve look further up when the exosphere gets closer (at about 700 km or so, according to Wikipedia)? What is the max temperature the thermosphere will reach?