Cubic centimeter, and it depends on where. For instance, in the Solar System, between stars, or between galaxies? In the Solar System, the solar wind has an ave

Cubic centimeter, and it depends on where. For instance, in the Solar System, between stars, or between galaxies? In the Solar System, the solar wind has an average density of 3 to 10 particles (mostly protons and electrons) per cc, but it's lower the farther out from the Sun.