Electromagnetic field dissipation and corpuscular bombardment and their implications in atmospheric modelling

The dissipation of energy of electric fields and currents in the polar auroral atmosphere is a major source of energy for the thermosphere ranging locally up to 100 ergs cm^?2 sec^?1 and perhaps more during the most intense disturbance. Globally the input of energy to the thermosphere can often exceed that due to solar EUV radiation. This energy source is always significant in polar regions and its variable strength with respect to that of the solar EUV radiation determines the behaviour of the middle and low latitude thermosphere. It is extremely difficult to model because of its variability in space and time. Nevertheless understanding the dynamics and composition of the global thermosphere is dependent upon incorporation of this source realistically into models. A further important aspect of this energy source is the consequences of its action in changing the density and composition of the thermosphere globally leading to subsequent changes in the absorption of solar EUV radiation. The ring current may also, at times, be a significant source of energy to the low latitude thermosphere.