exobase

== English == === Etymology === From exo- +‎ base. === Noun === exobase (plural exobases) The base altitude of the exosphere, where particles often escape the atmosphere as it blends into space. ==== Usage notes ==== The exobase is commonly treated as the top of the conventional atmosphere of thick atmospheres. A more complex definition would be the top of the neutral atmosphere. ==== Synonyms ==== exopause critical altitude