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We have completed computer simulations of the inner magnetosphere, for the substorm-type event of 19 September 1976. Several computer runs have been performed, with various sets of input parameters. Data from the Air Force S3-2 satellite and ground magnetometers were used for model inputs. Model predictions were analyzed and exhaustively compared with data from the S3-2 satellite, the AFGL magnetometer chain and many other sources. Agreement between theory and data was very satisfactory in most respects. The model injected a realistic ring current during the substorm. Many features of various types of observations were correctly predicted by the model, which was then used to suggest physical interpretations of the features. The predicted latitudinal distribution of region-2 Birkeland currents disagrees with S3-2 observations in a way that appears to be independent of details of the model, input inaccuracies, etc. Some implications of this discrepancy for the theory of the plasma sheet and magnetospheric substorms have been worked out. The computed total Joule heating rate in our modeling region is larger than would be estimated by a standard method, and the time-integrated Joule heating rate is about twice the change in model ring-current energy. Recently, our program has been converted for use in modeling a magnetic storm and one run has been made through the first few hours of the magnetic storm of 29 July 1977. A realistic model ring current was injected in the first few hours after the sudden commencement.

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. We have developed a self-consistent quantitative model to compute electric fields, currents and the resulting plasma flow in the inner-magnetosphere/ionosphere system (L or = 10); parallel electric fields and ionospheric neutral winds are not included. The model was tested for 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 the 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 were consistent with most of the established features of convection in the inner magnetosphere., See also AD-A087 700.

Several results of the computer simulation of the behavior of the inner magnetosphere during the substorm-type event of 19 September 1976 are discussed. The model predicts a modest ring-current injection, in to about L=6, with total strength that is approximately equal to the strength estimated from the observed decrease in Dst. For the geosynchronous-orbit region on the dusk side, the model predicts a characteristic energy dispersion often observed by McIlwain and collaborators. The computed electric fields compare satisfactorily with electric fields measured from S3-2, although there are detailed differences. The predicted east-west magnetic perturbations due to region-2 Birkeland currents agree satisfactorily with S3-2 observations with regard to direction, total magnitude and general location, but there is an important general discrepancy: in most cases, the actual Birkeland currents were distributed over a wider range of latitude than the model would predict. The model Birkeland currents agree satisfactorily with the averaged observations of Iijima and Potemra, in terms of direction, strength and overall pattern. The model provides a useful picture of the overall magnetosphere-ionosphere current system. The model indicates that the total Joule heating during the event is about 2-3 times the increase in ring-current energy, a result that is in apparent contradiction to some previous estimates., See also AD-A087 699.

Results of the Rice University substorm simulation have been used to investigate the penetration of substorm-associated electric fields into the plasmasphere. Near 4 R(E) 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 obtained during magnetically disturbed periods. By assuming an 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 dust 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. (Author)

Several computer runs simulating the behavior of the inner magnetosphere during a substorm-type event that occurred on 19 September 1976, have been completed and analyzed. The computer model simulates many aspects of the behavior of the closed-field-line portion of the earth's magnetosphere, and the auroral and subauroral ionosphere. For these regions, the program self-consistently computes electric fields, electric currents, hot-plasma densities, plasma velocities and other parameters. Presented here are some highlights of the results of the event simulation. Predicted electric fields for several times during the event agree reasonably well with corresponding data from satellite S3-2. Detailed discussion is presented for a case of rapid subauroral flow that was observed on one S3-2 pass and is predicted by computer runs. The computed global distribution of Birkeland current agrees reasonably well with the observations of IIjima and Potemra. In the simulated substorm-type event, plasma-sheet ions are injected earthward of synchronous orbit near midnight and drift westward, forming a ring half-way around the earth by the end of the simulation, 3 hours after substorm onset. The dispersion of ion energies on the dusk side near synchronous orbit has the form commonly observed by McIlwain and collaborators. It appears that the ions would form a complete ring if the simulation were continued for several more hours.

We have completed four computer runs simulating the behavior of the earth's inner magnetosphere during the substorm-type event that had its onset at about 1000 UT on 19 September 1976. Our program simulated many aspects of the behavior of the closed-field-line portion of the auroral and subauroral ionosphere. For these regions, the program self-consistently computes electric fields, electric currents, hot-plasma densities, plasma flow velocities and other parameters. Our computed ionospheric electric fields compare reasonably well with corresponding data from satellite S3-2. The most striking observational feature of the electric fields in the modeled region during the 19 September 1976 event was an instance of rapid subauroral flow, which was observed on the outbound part of pass 4079B South and was also predicted by the computer runs. These computer results seem consistent with a simple analytic model for rapid subauroral flow developed by Southwood and Wolf. Birkeland-current densities predicted by the model are presented, for eventual comparison with S3-2 magnetometer data. A program has been developed to follow the evolution of the plasmasphere, or any other magnetospheric or upper-ionospheric cold-plasma boundary, through a modeled event. Some interesting preliminary results for computed plasmasphere shapes are presented. (Author)

The first simulation run of a magnetospheric substorm was successfully completed. The computer program was developed to simulate aspects of the behavior of the closed-field-line portion of the earth's magnetosphere, and the auroral and subauroral ionosphere, during a magnetospheric event. The program self-consistently, computes electric fields, electric currents and plasma flow velocities in these regions. The basic program has been run for several idealized cases, and various output and plotting routines have been developed. Electron-flux data and polar-cap electric-field data from the S3-2 satellite have been used to specify input for the program. Computed electric fields in the auroral zone have been compared with measurements from the S3-2 satellite, and the agreement is found to be reasonably good considering that this is our first try. Various features of the data are interpreted in terms of the model. The computed time-evolution of the particle distribution near geosynchronous orbit agrees reasonably well with what is normally observed by McIlwain and collaborators during substorms., Also sponsored under Grants, NSF-ATM74-21185, NGR-44-006-012 and NGL-44-006-012.

A quantitative model is developed for computing currents and electric fields in the area covered by the poleward set of field-aligned currents (region-1 Birkeland currents). The high-latitude band considered carries most of the westward electrojet and lies just poleward of the region treated in the Rice University computer simulation (which covers the inner magnetosphere and corresponding ionosphere); the present high-latitude-current model supplements the inner-magnetosphere simulations to make them nearly global. Birkeland current and aurorally enhanced conductivity are assumed to be uniformly distributed across the band. The area poleward of the band is taken to be an insulator, while boundary conditions at the lao-latitude edge of the band are derived from the results of the lower-latitude computer simulations of the substorm event that occurred on September 19, 1976. The time-dependent conductivity model used is based on electron fluxes and mean energies measured from the Air Force S3-2 satellite. Ionospheric electric fields and currents are calculated; ionospheric neutral winds are neglected. Model prediction of the locations of the electric-field reversal agree well with typical 0G0-6 stellite observations. Joule heating of the upper atmosphere, as inferred from calculation of currents and electric fields in the high-latitude region considered here, was found to be about 2 x 10 to the 11th power watts during the substorm period, somewhat less than the value estimated for the lower-latitude region (region-2 and below).