Kinetic Parameters of the Fractal Stellar Medium in the Vicinity of the Sun

This paper estimates the kinetic parameters of the fractal stellar medium in the vicinity of the Sun. In this regard, the main stages in the development of ideas about fractal structures in the stellar medium of galaxies are presented. This study is based on an investigation of the spatial distribution of 200\,000 stars of all spectral classes at distances from 1 to 100\;pc from the Sun, based on Gaia\;DR2 data. The results indicate the presence of fractal structures in the solar neighborhood with a fractal dimension of \mbox{$D\approx 2.41$}. Based on these data, the kinetic properties of the fractal stellar medium are studied. The role of irregular forces and paired stellar encounters in the collisional kinetics of stellar systems is considered. It has been shown that kinetic parameters such as the effective interparticle (interstellar) distance, correlation length, dynamic friction coefficient, and impact parameter for a fractal stellar medium differ significantly from the corresponding parameters for a quasi-homogeneous medium with limited density fluctuations and depend on the fractal dimension. It has been found that the fractal structure of the stellar medium leads to a shortening of the relaxation time in the Galaxy.