Statistical height-dependent relative importance of the Lorentz force and Joule heating in generating atmospheric gravity waves in the auroral electrojets

Abstract

On the basis of 28 days of European Incoherent Scatter Common Program 1 mode data obtained between 1989 and 1991, we have determined statistical ratios of the Lorentz force (L) to the Joule heating rate terms (J) in generating atmospheric gravity waves in the auroral electrojets between 101 and 125 km altitudes. Under the altitude of 120 km the ratio (L/J) rapidly decreases with increasing height, indicating that the relative importance of the two sources is very critically dependent on altitude. Above this altitude, L/J is approximately constant with height. We have also derived a transition height of about 116 km. Under this height the Lorentz force is relatively important. Above this height, Joule heating dominates. Considering the effect of the neutral wind, relative deviations caused by the neutral wind are estimated at less than 10% between 101 and 125 km altitudes. Therefore we can ignore the effect of neutral wind on the ratio. In order to fulfill the demand, in practice, a statistical curve of the ratio with height has been provided. Copyright 2005 by the American Geophysical Union.