A simple model of the flux content of the distant magnetotail

Abstract

A simple model is presented which allows the profile of open flux within the magnetotail lobes to be determined from a knowledge of the present size of the polar cap and the past history of low‐latitude and high‐latitude dayside reconnection. The model shows that the nominal length of the tail is dependent on the elapsed time since reconnection of the oldest open field lines and that a much longer disconnected tail and wake can exist beyond this. The model is applied to two 8‐hour intervals of observations, which indicate that the length of the tail can vary by almost a factor of 10, between ∼400 and 4000 RE, in just a few hours. In addition, differing rates of lobe reconnection in the Northern and Southern Hemispheres are shown to lead to considerable differences in the lengths of the two magnetotail lobes.