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Related to thermosphere: ionosphere
The outermost layer of the atmosphere, between the mesosphere and interplanetary space, where air becomes extremely thin and temperatures increase steadily with altitude.
ther′mo·spher′ic (-sfîr′ĭk, -sfĕr′ĭk) adj.
(Physical Geography) an atmospheric layer lying between the mesosphere and the exosphere, reaching an altitude of about 400 kilometres where the temperature is over 1000°C
the region of the upper atmosphere, above the mesosphere, in which temperature increases continuously with altitude.
The outermost layer of the Earth's atmosphere, lying above the mesosphere and extending hundreds of miles into outer space. In the thermosphere, which includes the exosphere and most of the ionosphere, temperatures increase steadily with altitude.