Model simulation of the substorm - associated 3 injection of an observed plasma

9 [1] We present results from a Rice Convection Model simulation of the early expansion 10 phase of a substorm that occurred 22 July 1998. The theoretical basis of the simulation 11 is the idea that the plasma injected into the inner magnetosphere during a substorm 12 primarily consists of a low-content plasma bubble, which is made up of flux tubes with 13 lower values of the entropy parameter PV than their neighbors. As discussed in an 14 accompanying paper, to simulate this event, we carefully tailor model inputs to fit Geotail 15 observations of the bubble at XGSM 9 RE. We find that both potential and induction 16 electric fields play important roles in transporting and energizing the particles during 17 the event. The potential electric field associated with Birkeland currents that flow along 18 the east and west sides of the bubble (i.e., the substorm current wedge) is characterized by 19 a localized strengthening of the westward auroral ionospheric electric field within the 20 bubble, as well as the production of a region of enhanced westward flow just Equatorward 21 of the diffuse electron aurora. The inner edge of the modeled plasma sheet assumes a 22 dented-in form that is similar in shape to the injection boundary proposed many years ago 23 on observational grounds. Flux tubes that are pushed earthward ahead of the bubble at 24 onset form a sharp pressure peak near local midnight and geosynchronous orbit, and 25 the particles on those tubes contribute significantly to the injection of particles into the 26 inner magnetosphere.