NEUTRAL LINE MODEL OF SUBSTORMS - PAST RESULTS AND PRESENT VIEW

The near-Earth neutral line (NENL) model of magnetospheric substorms i s reviewed. The observed phenomenology of substorms is discussed inclu ding the role of coupling with the solar wind and interplanetary magne tic field, the growth phase sequence, the expansion phase (and onset), and the recovery phase. New observations and modeling results are put into the context of the prior model framework. Significant issues and concerns about the shortcomings of the NENL model are addressed. Such issues as ionosphere-tail coupling, large-scale mapping, onset trigge ring, and observational timing are discussed. It is concluded that the NENL model is evolving and being improved so as to include new observ ations and theoretical insights. More work is clearly required in orde r to incorporate fully the complete set of ionospheric, near-tail, mid tail, and deep-tail features of substorms. Nonetheless, the NENL model still seems to provide the best available framework for ordering the complex, global manifestations of substorms.