thermosphere


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Related to thermosphere: ionosphere

thermosphere

(ther -mŏ-sfeer) See atmospheric layers.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Thermosphere

 

the layer of the upper atmosphere located between the mesopause—that is, the upper boundary of the mesosphere—and the base of the exosphere. On the average, the thermosphere extends from a height of about 80 km to a height of about 500 km; these limits vary by ±10–20 percent. In English, the term “thermosphere” is often used in a broader sense to mean the region of the atmosphere extending from the mesopause to outer space. In the present article, the term is used in the narrower sense.

The thermosphere is characterized by a positive temperature gradient, which is equal to zero at the mesopause, has a maximum value between 100 and 200 km, and again becomes equal to zero near the base of the exosphere, where the atmosphere becomes practically isothermal. From the mesopause to the exosphere, the temperature increases approximately from 200°K to 1000°–2000°K. Temperature variations are especially large at the base of the exosphere.

The density of the thermosphere varies on the average from 1.8 × 10–8g/cm3 at a height of about 80 km to 1.8 × 10–15g/cm3 at a height of about 500 km. The relative content of the atmospheric components at the mesopause is similar to that at ground level, but the amount of oxygen in the atomic state increases with increasing height. At a level of about 120 km, the separation of gases by diffusion begins. Above the 200–300-km level atomic oxygen, which is lighter than molecular oxygen and nitrogen, becomes predominant; above 500 km, there are significant relative concentrations of even lighter elements, namely, hydrogen and helium. Some of the atoms and molecules in the thermosphere are ionized and are concentrated in several layers (seeIONOSPHERE).

All the characteristics of the thermosphere are subject to rather sizable variations, depending on geographic position, solar activity, season of year, and time of day. The temperature and dynamical conditions of the thermosphere are governed by the energy it absorbs. This energy may originate from nonterrestrial sources or the underlying troposphere.

The major sources of thermospheric energy are: hard solar electromagnetic radiation, which dissociates and ionizes the atmosphere; energetic charged particles (protons and electrons) that penetrate the high-latitude regions of the atmosphere during auroras; atmospheric molecules dissociated into atoms; gravity waves, which may originate both in the troposphere and in the upper atmosphere in the auroral region; and energy dissipation in the thermospheric circulation. The dominant constituents of the thermosphere are nitrogen and oxygen molecules and oxygen atoms, none of which can emit infrared radiation in large amounts. Thus, as a result of insufficient emissivity, the thermosphere is strongly heated, especially at great heights. Under these conditions, heat can be removed only by conduction to the mesopause as a consequence of the positive temperature gradient. A large number of complex molecules, such as carbon dioxide, water, and ozone, are present at the mesopause; these molecules are good emitters of infrared radiation and thus ensure that heat accumulated above the mesopause is removed from the atmosphere.

The thermosphere exerts a drag on artificial satellites, and the behavior of the ionosphere depends substantially on the state of the thermosphere.

REFERENCES

Okolozemnoe kosmicheskoe prostranstvo. Moscow, 1966. (Translated from English.)
Fizika verkhnei atmosfery Zemli. Edited by G. S. Ivanov-Kholodnyi. Leningrad, 1971. (Translated from English.)
Krasovskii, V. I. Shtili i shtormy v verkhnei atmosfere. Moscow, 1971.

V. I. KRASOVSKII

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

thermosphere

[′thər·mə‚sfir]
(meteorology)
The atmospheric shell extending from the top of the mesosphere to outer space; it is a region of more or less steadily increasing temperature with height, starting at 40 to 50 miles (70 to 80 kilometers); the thermosphere includes, therefore, the exosphere and most or all of the ionosphere.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

thermosphere

thermosphere
The layer of atmosphere above the mesosphere, which extends from 50 to 55 miles (80-90 km) above the sea level with the upper limit undefined. The temperature in this region initially rises rapidly with heights up to about 120 miles (200 km) and thereafter increases more slowly or not at all. Above 120 miles (200 km), the temperature varies between 600° and 2000°C (1100 and 3600°F), depending on the solar activity. The lower layers of the thermosphere contain enriched ozone.
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved
References in periodicals archive ?
Mlynczak and his colleagues have created the Thermosphere Climate Index (TCI), which measures how much NO is dumped from the thermosphere into outer space.
Overview of the temperature response in the mesosphere and lower thermosphere to solar activity.
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Wissing, "Interannual variation of NOx from the lower thermosphere to the upper stratosphere in the years 1991-2005," Journal of Geophysical Research, vol.
Abstract: A talk on the Rosetta mission and information on the 3 EU CubeSat missions currently being worked on, i.e QB50-50 CubeSats will be launched in Jan 2016 at low altitude to take measurements of the thermosphere and do re-entry research.
The company added that its Emprint Ablation System with Thermosphere Technology is designed to precisely heat and destroy diseased soft tissue (including liver, lung and kidney), and non-resectable liver tumors.
The QB50 program will study in situ the temporal and spatial variations of a number of parameters in the lower thermosphere using a network of around 40 double CubeSats carrying identical sensors.
Summary: The Republic of Lebanon is set to reignite its space program, more than 40 years after the first Lebanese rocket ascended 140 kilometers into the thermosphere. In a landmark decision, the new government is seeking funding for a multimillion dollar program that could see the country send an astronaut into space within a decade, sources...
Hedin, "Extension of the MSIS thermosphere model into the middle and lower atmosphere," Journal of Geophysical Research, vol.
In the middle atmosphere (10-100km altitude), consisting of the stratosphere (10-50 km), the mesosphere (50-90 km) and a part of the lower thermosphere (90-150 km), the zonal wind velocity can reach magnitudes as large as 80m/sin mid-latitudes at an altitude of about 50 km.