The solar wind is part of the Sun’s outer atmosphere, expanding outwards and carrying the solar magnetic field with it. Solar wind velocity near the Earth is commonly around 400 km s-1 but with frequent highspeed streams with velocities around 700 km s-1 and sometimes beyond 1 000 km s-1. Earthorbiting satellites and those in L1 and L2 see solar wind fluctuations at different times but otherwise do not observe noticeable differences in solar wind characteristics.
On average, the solar wind is made up mostly of protons (95%), with 4% alpha particles and around 1% minor ions, of which carbon, nitrogen, oxygen, neon, magnesium, silicon and iron are the most abundant [RD.5].
In interplanetary space, solar wind average density varies, to a good approximation with r-2(where r is radial distance from the Sun) in the range ±40 degrees solar latitude. The average electron temperature has been seen to vary as r-0,64 for r between 1,52 to 2,31 AU. Ion velocity does not show a significant radial variation.