Investigation Of Bow Shock Shape And Magnetopause Pressure Balance

The solar wind-magnetosphere coupling is one of the most crucial portions in the investigation of solar-terrestrial space physics. And the terrestrial bow shock and magnetopause are two very important interfaces in solar wind-magnetopause coupling. When the solar wind flows to Earth and through the bow shock, the plasma parameters and magnetic field change obviously. The magnetopause is the boundary of the magnetopause, and separating the solar wind and earth’s magnetosphere. The variations of upstream solar wind could change the shape and location of the magnetopause, and then influence the structure of the magnetic field in the earth’s magnetosphere.In this master dissertation,several satellites’ data is used to investigate the relationsh,ip between different upstream solar wind parameters and the shape and size of terrestrial bow shock. And a three-dimensional asymmetrical bow shock model was built which include the dipole tilt angle as one of its factors. We use the simulated results of a solar wind event on 5 June 1998 which from a three-dimensional magnetohydrodynamic (MHD) model, SWMF, to investigate the balances of the dynamic, thermal and magnetic pressure along the Sun-Earth line for the different conditions of IMF. The research contents of this dissertation are as follows:We use multiple satellites’ bow shock crossing data, and analyze the effect from Z component of IMF, solar wind dynamic pressure, magnetoacoustic Mach number,the value of β and the dipole tilt angle to the shape and size of bow shock. A global three-dimensional asymmetrical bow shock model was built which include above 5 factors. Compared with the previous bow shock model, our model not only could present the flaring angle and rotational asymmetry, but also reflect the variations of shape and size of bow shock with different dipole tilt angles. In the northern hemisphere, the flaring angle increases with positively increasing dipole tilt angle,but almost has no change with negatively increasing dipole tilt angle. And the rotational asymmetry in the northern hemisphere is larger than that in the southern hemisphere when the dipole tilt angle is positive. In contrast, in the southern hemisphere, the flaring angle increases with negatively increasing dipole tilt angle,but almost has no change with positively increasing dipole tilt angle. And the rotational asymmetry in the southern hemisphere is larger than that in the northern hemisphere when the dipole tilt angle is negative.A three-dimensional adaptive MHD model, SWMF,is used to simulate the interaction between the solar wind and magnetosphere for a particular event on 5 June 1998 and the simulated results of this event is used to investigate the balances of the dynamic, thermal and magnetic pressure along the Sun-Earth line for the different conditions of IMF. We found that along the Sun-Earth line, the thermal pressure is dominant on the magnetopause in southward IMF,while the magnetic pressure is dominant on the magnetopause in northward IMF. The magnetic reconnection easily occurs for southward IMF, and results in magnetic pressure decreasing just inside the magnetopause. This factor plays a pivotal role in the earthward displacement of the Earth’s magnetopause for southward IMF. And the increasing of thermal pressure just outside the magnetopause also has contribution to this displacement, especially for lower IMF.