Since physical processes in the magnetopause can be observed in the high-latitude ionosphere via field lines and current systems, ground magnetic field responses to solar wind and IMF changes can provide valuable information on dayside transient phenomena involved in solar wind-magnetosphere-ionosphere coupling process.

The basic processes at the magnetopause boundary are magnetic reconnection, and viscous-like interaction, such as Kelvin-Helmholtz instability (KHI) and pressure-pulse drive. The magnetic reconnection occurs preferentially at the region where magnetosheath largest when the IMF is southward. On the other hand, the KHI is generally known to be driven by the velocity shear with a rapid magnetosheath plasma at the boundary for northward IMF condition. The magnetosphere boundary can also fluctuate in response to solar wind dynamic pressure pulse. However, it still need to be understood what kind of factors of magnetopause boundary are more important depending on the solar wind and IMF conditions.

We have studied magnetospheric dynamics and ionospheric phenomena by using a high-resolution 3-D global MHD simulation of the solar wind and planetary magnetosphere interaction as a function of IMF condition. The results of these studies will be presented.