Global and local estimates of the current sheet thickness: CDAW-6

Abstract

The growth phase development of the near-Earth magnetotail configuration during the CDAW-6 substorm (22 March 1979, 1054 UT) is studied using two complementary methods. The global magnetic field configuration is modeled using data from two suitably located spacecraft and temporally evolving variations of the Tsyganenko magnetic field model. These results are compared with a local calculation of the current sheet location and thickness previously carried out by McPherron et al. /1/. The good agreement between the two methods provides a positive test for the accuracy of the global model. Both models indicate the formation of an extremely thin current sheet during the substorm growth phase. The plasma electron data together with the rate of pitch-angle scattering estimated from the global field model suggest that the onset may be initiated by the chaotization of electrons and consequent growth of the tearing instability.