Analysis of the steady state available energy budget in the high-latitude lower thermosphere

With increasingly negative IMF B-z values APE density intensifies more significantly than KE density above about 123 km, while KE density intensifies more significantly than APE density below. KE is generated primarily where the ion-drag force associated with plasma convection accelerates the neutral gas and is destroyed primarily where the ion-drag force opposes the wind. APE is generated primarily where Joule heat is deposited in regions of elevated temperatures and destroyed where the heat is deposited in regions of reduced temperatures.

Ion drag is generally more important than Joule heating for generating AE for steady-state conditions, but the relative contribution of the ion-drag forcing compared with heating decreases with descending altitude. AE generation by Joule heating intensifies more significantly than generation by ion drag with increasingly negative IMF B-z values. Transport of AE by horizontal and vertical winds is a significant component of the AE budget.

Conversion of APE to KE, and of KE to APE, constitutes an important part of their budgets.