Nonstationary interaction between solar wind and interstellar matter.

The small perturbation method is used to study the deviations of the distant solar wind from spherical symmetry that are due to interaction of the solar wind with interstellar neutral hydrogen. This interaction is in the form of photoionization and charge exchange. Changes in the ionization rate of neutral galactic gas in the heliosphere caused by solar activity influence the deceleration of the solar wind and cause temperature fluctuations of the order of 10-20% in the vicinity of the orbits of Saturn and Neptune.