Paper#: 155
Poster #:
Session Name: Plenary
Room: West Ballroom
Day: Monday
Time: 9:45-10:10 a.m.
Abstract Title: Strengths and Weaknesses of Global MHD Simulations of Substorms
PresentSurname: Lyon, J.G.
All Authors: J.G. Lyon, M. Wiltberg, J. Fedder, C. Goodrich, S. Slinker
Abstract : We will discuss the successes and failures of global MHD simulations of substorms. The successes are impressive. They include correct calculation of substorm onset and subsequent development of ionospheric currents at least for a number of isolated substorms. From a physics point of view, the simulations allow us to track the global energy flow, particularly the Poynting flux. We will show that this flow is similar in the growth and expansion phases of substorms, but that underlying field and plasma configuration changes at onset. The MHD simulations also show a way to reconcile, at least partially, the near-Earth neutral line (NENL) and current disruption models. This reconciliation is tied to the appearance in the simulations of narrow flow channels which we're tempted to equate to bursty bulk flows (BBF's). These flow channels can have action initiated at the NENL (20-30 Re), yet a satellite in the nearer-Earth tail can see consequences that appear to indicate initiation Earthward of the satellite's position. The areas in which MHD fails or at least has little to say are those where either the physics or the numerical resolution break down -- such as thin current sheets (including violent instabilities seen at onset) and such as high mode number ballooning instabilities.