On the processes in the terrestrial magnetosheath 2. Case study

We test a new scheme to study the magnetosheath. The scheme uses the solar wind measurements as the input into the gasdynamic convected field model, a nd the model output is compared with magnetosheath observations. In our fou r test cases there is a significant overall success in the model prediction . This scheme works better than other methods in magnetosheath studies and is potentially useful for space weather forecasts and nowcasts. The directi on of the magnetic field is modeled most accurately. The prediction of the size of the magnetosphere is accurate within a few percent. The predicted t hickness of the magnetosheath is accurate up to 90%. With a double-normaliz ation procedure developed in this study, we are able to separate the proces ses intrinsic in the magnetosheath from those due to large-scale upstream t emporal variations. The test cases confirm the existence of a compressional front one third of the distance from the magnetopause to the bow shock nea r the stagnation streamline. The magnetosheath density profile near the sta gnation streamline is consistent with the models that add a compressional f ront between the two depletion processes described by the plasma depletion model. A major unexpected feature is that the magnetosheath flow pattern is very different from that described by the model and maybe by most other mo dels, including MHD models. The magnetosheath flow near the stagnation stre amline does not slow down gradually toward the stagnation point. It moves r apidly until reaching a very small region near the magnetopause.