The top of the homosphere is called the homopause, also known as the turbopause. Above the homopause is the heterosphere, where diffusion is faster than mixing, and heavy gases decrease in density with altitude more rapidly than lighter gases.
The apex of the homosphere is known as the homopause or the turbopause. In the region above this point, the heterosphere exists, characterized by faster diffusion compared to mixing, and heavy gases experience a greater decrease in density relative to light gases with increasing altitude.