Nature

https://en.wikipedia.org/wiki/Heliosphere

Edge structure

The outer structure of the heliosphere is determined by the interactions between the solar wind and the winds of interstellar space. The solar wind streams away from the Sun in all directions at speeds of several hundred km/s in the Earth's vicinity. At some distance from the Sun, well beyond the orbit of Neptune, this supersonic wind slows down as it encounters the gases in the interstellar medium. This takes place in several stages:

• The solar wind is traveling at supersonic speeds within the Solar System. At the termination shock, a standing shock wave, the solar wind falls below the speed of sound and becomes subsonic.
• It was previously thought that once subsonic, the solar wind would be shaped by the ambient flow of the interstellar medium, forming a blunt nose on one side and comet-like heliotail behind, a region called the heliosheath. However, observations in 2009 showed that this model is incorrect.[13][14] As of 2011, it is thought to be filled with a magnetic bubble "foam".[15]
• The outer surface of the heliosheath, where the heliosphere meets the interstellar medium, is called heliopause. This is the edge of the entire heliosphere. Observations in 2009 led to changes to this model.[13][14]
• In theory, heliopause causes turbulence in the interstellar medium as the Sun orbits the Galactic Center. This turbulence results from the pressure of the advancing heliopause against the interstellar medium. However, the velocity of the solar wind relative to the interstellar medium may be too low for a bow shock.[16]