thermosphere

[ thur-muh-sfeer ]

noun

1. the region of the upper atmosphere in which temperature increases continuously with altitude, encompassing essentially all of the atmosphere above the mesosphere.

thermosphere

/ ˈθɜːməˌsfɪə /

noun

1. an atmospheric layer lying between the mesosphere and the exosphere, reaching an altitude of about 400 kilometres where the temperature is over 1000°C

thermosphere

/ thûr′mə-sfîr′ /

1. The region of the Earth's upper atmosphere lying above the mesosphere and extending from a height of approximately 80 km (50 mi) to between 550 and 700 km (341 and 434 mi) above the Earth's surface. In the thermosphere temperatures increase steadily with altitude, reaching as high as 1,727°C (3,140°F) at the highest elevations. Chemical reactions occur much faster here than on the surface of the Earth.
2. See also exosphereSee illustration at atmosphere

Word History and Origins

Origin of thermosphere¹

First recorded in 1950–55; thermo- + sphere

Example Sentences

The extra CO2 pumped into the atmosphere down the years has cooled some of its highest reaches - the thermosphere.

From BBC

Luckily for Morgan, he was able to send his ballot to Lawrence County’s Department of Voter Services electronically, from the thermosphere.

From Washington Post

Then I’d think upward in expanding rings of thinning air: troposphere, stratosphere, mesosphere, thermosphere, exosphere.

From New York Times

Sinking air from the thermosphere above in the wintertime has the opposite effect and warms.

From Washington Post

If you’re counting the distance to space in atmospheric layers, Virgin Galactic reached the bottom of the second-highest layer, known as the thermosphere.

From Washington Times