Thesis (M.Sc.)--Chulalongkorn University, 2000

The Sun is the origin of a flow of plasma (ionized gas) called the solar wind, and the Earth orbits the Sun while its magnetosphere is pelted by the solar wind at a speed of about 400 km/s. In addition, the entire solar system orbits the center of our Milky Way Galaxy, and from the point of view of the solar system, there is a flow of atoms and ions from the interstellar medium impacting with a speed of about 26 km/s. Where the two flows collide, neutral atoms from the interstellar medium can undergo charge exchange with protons from the solar wind. This has an important effect on the predicted structure of the region near the outer edge of the solar system, which has not yet been explored by spacecraft. (The solar system is estimated to extend 80-160 AU from the Sun.) In this work we therefore study the evolution of the phase space distribution function of hydrogen atoms due to collisions between stoms and ions by solving the Boltzmann equation.