The exopause is the imaginary 'edge' of the atmosphere of the earth or another planetary celestial body. According to one definition, it is the spherical shell, outside of which the force on neutral hydrogen atoms due to the radiation pressure of the sun is greater than the gravitational attraction of the body. The atoms are already moving on ballistic paths in the exosphere below , since collisions are very rare.
The exact boundary between the exosphere and the exopause is not well known. Complex analytical and numerical modeling is necessary here. The characterization of exoplanets gives research a new boost. Based on current calculations, it is assumed that the earth's exopause is about 36 earth radii away from the earth. Converted, this distance corresponds to an altitude of about 223,000 km above the earth's surface or about 58% of the mean distance to the moon .
- James Bishop: Analytic Exosphere Models for Geocoronal Applications (PDF file; 958 kB), Planet. Space Sci., 39: 885-893 (1991).
- A. Beth, P. Garnier, D. Toublanc, I. Dandouras, C. Mazelle: Theory for planetary exospheres: II. Radiation pressure effect on exospheric density profiles . In: Icarus . tape 266 , March 2016, ISSN 0019-1035 , p. 423-432 , doi : 10.1016 / j.icarus.2015.08.023 ( elsevier.com [accessed May 2, 2018]).