Solar wind observations by Lyman alpha

The interaction between the solar wind and the local interstellar matter takes place at two distinct regions. The plasma component of the interstellar matter meets the solar wind at the heliospheric interface region and it is excluded from entering into the heliosphere. The neutral component consisting mainly of hydrogen atoms flows through the whole heliosphere. It gets, however, partly ionised by charge exchange collisions with solar wind protons and energetic photons from the Sun. The neutral atom trajectories will also be affected by the radiation pressure from the Sun. While the properties of the interface region are still too sparsely known to be useful for solar wind studies the neutral H distribution near the Sun has been used successfully for this purpose. Measurements of Lyman alpha light scattered by neutral hydrogen atoms will serve as a remote sensing measurement of the solar wind’s spatial and temporal distribution. In this work we consider the state of the interplanetary Lyman alpha modelin...