The turbopause, also called the homopause, marks the altitude in an atmosphere below which turbulent mixing dominates.
[1] The region below the turbopause is known as the homosphere, where the atmosphere is well mixed for chemical species which have long mean residence times.
The region above the turbopause is the heterosphere, where molecular diffusion dominates and the chemical composition of the atmosphere varies according to chemical species and their atomic weight.
Earth's turbopause lies near the mesopause, at the intersection of the mesosphere and the thermosphere, at an altitude of roughly 90 km (56 mi).
[3] It was discovered by French scientists following the firing of two Véronique sounding rockets on 10 and 12 March 1959.