Model simulation of the substorm - associated 3 injection of an observed bubble into the inner magnetosphere : 4 1 . Magnetic field and other inputs

8 [1] The objective of this work is a realistic Rice Convection Model (RCM) simulation of 9 a modest substorm that occurred on 22 July 1998 and was observed by the Geotail 10 spacecraft in the inner plasma sheet. It represents the first time the RCM has been used for 11 detailed modeling of an inner magnetospheric event using data from a spacecraft in the 12 inner plasma sheet beyond geosynchronous orbit to drive the model’s time-dependent 13 boundary conditions. Since this represents a substantial departure from past practice, we 14 present, in this paper, a detailed account of how model inputs are determined. An 15 accompanying paper presents results and interpretations. Model inputs are adjusted to 16 achieve approximate consistency between RCM-computed values and measurements by 17 Geotail, which was within the RCM modeling region near XGSM = 9 RE, YGSM = 0. To 18 represent the magnetic field in the growth phase, we utilize a Tsyganenko (1989) statistical 19 magnetic field model, adjusted to agree with Geotail-measured pressure and magnetic 20 field in a new way using analytic solutions to the linear Grad-Shafranov equation. The 21 magnetic field during the expansion phase is represented by adding a substorm current 22 wedge using formulas developed by Tsyganenko. Induction electric fields play a 23 central role in these simulations, because they are large in the vicinity of the substorm 24 injection region. We provide a detailed description of how induction electric fields are 25 included in the RCM as well as a prescription of the electromagnetic gauge condition 26 used in the code.