Evaluation of the Total Magnetospheric Energy Output Parameter, U/sub T/

摘要

Over the last few years the relationship between U/sub T/, the magnetospheric energy consumption or output rate, and epsilon, a commonly used solar wind-magnetosphere energy input function, has been explored in some detail. Very high correlations between U/sub T/ and epsilon are found during periods of strong activity, and by using linear prediction filtering techniques a ''delta-function'' impulse response was found for filter elements representing essentially zero delay. In light of these remarkable results, the derivation of U/sub T/ for these intervals is re-examined. We find that U/sub T/ is dominated in each event interval by the term containing tau/sub R/, the ring current decay time, and that when tau/sub R/ is defined as a function of epsilon the ''delta-function'' impulse response is present. If a constant tau/sub R/ is assumed, the delta-function part of the filter disappears completely. Thus, this delta-function, which has been taken as being indicative of the directly driven component is an artifact of the earlier analysis, and it is due to the dependence of U/sub T/ on epsilon. Our results imply that until U/sub T/ can be derived independently from epsilon, these two quantities cannot be compared in a meaningful way, and that results obtained in previous studies are not valid. (ERA citation 11:024259)