Global three-dimensional MHD simulation of a space weather event: CME formation, interplanetary propagation, and interaction with the magnetosphere

A parallel adaptive mesh refinement (AMR) finite-volume scheme for predicti ng ideal MHD flows is used to simulate the initiation, structure, and evolu tion of a coronal mass ejection (CME) and its interaction with the magnetos phere-ionosphere system. The simulated CME is driven by a local plasma dens ity enhancement on the solar surface with the background initial state of t he corona and solar wind represented by a newly devised "steady state" solu tion. The initial solution has been constructed to provide a reasonable des cription of the time-averaged solar wind for conditions near solar minimum: (1) the computed magnetic field near the Sun possesses high-latitude polar coronal holes, closed magnetic field flux tubes at low latitudes, and a he lmet streamer structure with a neutral line and current sheet; (2) the Arch imedean spiral topology of the interplanetary magnetic field is reproduced; (3) the observed two-state nature of the solar wind is also reproduced wit h the simulation yielding fast and slow solar wind streams at high and low latitudes, respectively; and (4) the predicted solar wind plasma properties at 1 AU are consistent with observations. Starting with the generation of a CME at the Sun, the simulation follows the evolution of the solar wind di sturbance as it evolves into a magnetic cloud and travels through interplan etary space and subsequently interacts with the terrestrial magnetosphere-i onosphere system. The density-driven CME exhibits a two-step release proces s, with the front of the CME rapidly accelerating following the disruption of the near-Sun closed magnetic field line structure and then moving at a n early constant speed of similar to 560 km/s through interplanetary space. T he CME also produces a large magnetic cloud (> 100 R-S across) characterize d by a magnetic field that smoothly rotates northward and then back again o ver a period of similar to2 days at 1 AU. The cloud does not contain a sust ained period with a strong southward component of the magnetic field, and, as a consequence, the simulated CME is somewhat ineffective in generating s trong gee-magnetic activity at Earth. Nevertheless, the simulation results illustrate the potential, as well as current limitations, of the MHD-based space weather model for enhancing the understanding of coronal physics, sol ar wind plasma processes, magnetospheric physics, and space weather phenome na. Such models will provide the foundation for future, more comprehensive space weather prediction tools.