This and the following two papers report results of the first comprehensive computer simulation of the behavior of the earth's inner magnetosphere during a substorm‐type event. Our computer model self‐consistently computes electric fields, currents, and plasma distributions and velocities in the inner‐magnetosphere/ionosphere system (L ≲10); parallel electric fields and ionospheric neutral winds are not included. In this paper, we derive the basic equations of the model, describe the inputs, and present an overview of results. The first appendix presents derivations of general, useful laws of bounce‐averaged gradient, curvature, and drifts in a plasma with isotropic pitch angle distributions. A second appendix describes the numerical method used in our computer simulation. The succeeding two papers present analyses of model results and comparisons with data. The model was applied to a substorm‐type event that occurred on September 19, 1976. Satellite data (primarily from the Air Force S3‐2 satellite) were used extensively both for boundary conditions and for comparisons with model predictions. Other data were also used as input for our time dependent magnetic field and conductivity models. The S3‐2 data for the event show some novel features, independent of the simulation. Dawn‐dusk electric fields show a general correlation with east‐west magnetic field perturbations. Unexpectedly, two of the passes display substantial regions of sunward plasma flow poleward of the main part of the region 1 Birkeland currents. The cross‐polar cap potential drops computed from the data represent the first effort at satellite monitoring of this important parameter during various phases of a substorm, and show an important enhancement during the substorm. Numerical results from these first‐try simulations are consistent with most of the established features of convection in the inner magnetosphere, such as generally sunward flow, shielding of the potential electric field for L <5, and the tendency for stronger electric fields on the duskside than on the dawnside. In addition, the model reproduces some typical substorm phenomena, such as energy‐dependent particle injection with a dawndusk asymmetry and establishment of a partial ring current.

We present preliminary results of a magnetospheric substorm that occurred on applying the Rice convection model to the early September 19, 1976 [Harel et al., 1981a,b; Spiro main phase of the magnetic storm of July 29, et al., 1981; Karty et al., 1982; Chen et al., 1977. The computer model self-consistently com-1982]. The relationship of the Rice convection putes electric fields and currents, as well as model to other related theoretical formulations, plasma distributions and velocities, in the and our model's basis in earlier research, were inner-magnetosphere/ionosphere system. In the described in Harel et al. [1981a]. For the sake 1present address is Mail Code 144-218, Jet Pro-B. Formulation

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Results of the Rice University substormn simulation have been used to investigate the penetration of substorm-associated electric fields into the plasmasphere. Near 4 RE) in the equatorial plane, our time-dependent electric field model is characterized by eastward components in the dusk-midnight local time sector and westward components after midnight. Except for a small region Just before dusk the model predicts eastward electric field components throughout the daytime sector. The characteristic radial component is directed-\-inward at all local times except for a small region just after dawn. These results compare favorably with available whistler and incoherent scatter measurements obtainid during magnetically disturbed periods.By assUmingan initial plasmapause shape and by following the computed E x B drift trajectories of plasma flux tubes from that initial boundary we have examined the short-term evolution of the plasmapause during the substorm-like event of 19 September 1976. We find that narrow filamentary tails can be drawn out from the plasmasphere near dusk within hours of substorm onset. These tail-like appendages to the plasmasphere subsequently drift rapidly from the dusk sector toward the daytime magnetopause.Investigation of the large-scale time-dependent flow of plasma in the evening sector indicates that some mid-latitude plasma flux tubes that drift eastward past the dusk terminator reverse their motion between dusk and midnight and begin to drift westward toward dusk. Such time-dependent changes in flow trajectories may be related to the formation of F-region ionization troughs. " ' tea.Unclassified -