[The evaluation of parameters pertinent to the excitation in aurora with a time-domain recursive...

The time-domain expression and spectral analysis of the combined direct and indirect excitation process in aurora are described. The technique to evaluate the parameters pertinent to the excitation in aurora with a time-domain recursive instrumental-variables algorithm was studied. The parameters thus determined compare favourably with those evaluated by means of a non-recursive cross-spectral technique. A modification to the algorithm allows the tracking of changes in the excitation mechanism by evaluating parameters which vary in time. Processing of real auroral photometric measurements with this method has established the existence of such changes and demonstrated their time history.