Abstract

Intense small-scale Joule heating structures can induce mixing of thermospheric constituents, which may significantly supplement the mixing caused by the global-scale meridional circulation driven by the total Joule heating. Associated with the net upward flux of molecular nitrogen and oxygen due... Show moreIntense small-scale Joule heating structures can induce mixing of thermospheric constituents, which may significantly supplement the mixing caused by the global-scale meridional circulation driven by the total Joule heating. Associated with the net upward flux of molecular nitrogen and oxygen due to the small-scale mixing is an additional upward heat flux. The relative importance of small-scale mixing, as compared with the importance of mixing by the meridional circulation, likely increases with magnetic activity. A parametrization is presented in terms of an effective eddy diffusivity. For a moderately active level of Joule heating, the effective eddy diffusivity may be a sizable fraction of molecular diffusivity between 120~km and 250~km altitude at auroral latitudes. Show less