Rice Convection Model simulation of the substorm‐associated injection of an observed plasma bubble into the inner magnetosphere: 2. Simulation results

Abstract

We present results from a Rice Convection Model simulation of the early expansion phase of a substorm that occurred 22 July 1998. The theoretical basis of the simulation is the idea that the plasma injected into the inner magnetosphere during a substorm primarily consists of a low‐content plasma bubble, which is made up of flux tubes with lower values of the entropy parameter PV 5/3 than their neighbors. As discussed in an accompanying paper, to simulate this event, we carefully tailor model inputs to fit Geotail observations of the bubble at X GSM ≈ −9 R E . We find that both potential and induction electric fields play important roles in transporting and energizing the particles during the event. The potential electric field associated with Birkeland currents that flow along the east and west sides of the bubble (i.e., the substorm current wedge) is characterized by a localized strengthening of the westward auroral ionospheric electric field within the bubble, as well as the production of a region of enhanced westward flow just Equatorward of the diffuse electron aurora. The inner edge of the modeled plasma sheet assumes a dented‐in form that is similar in shape to the injection boundary proposed many years ago on observational grounds. Flux tubes that are pushed earthward ahead of the bubble at onset form a sharp pressure peak near local midnight and geosynchronous orbit, and the particles on those tubes contribute significantly to the injection of particles into the inner magnetosphere.