An article at physorg describes why and how the solar wind experiences an increase in temperature and speed after it leaves the sun's surface and encounters the deep freeze of space. Interesting science! I love the description of how NASA will learn more:
Solar Probe Plus, scheduled for launch in 2018, will plunge so far into the sun's atmosphere that the sun will appear as much as 23 times wider than it does in the skies of Earth. At closest approach, about 7 million km from the sun's surface, Solar Probe Plus must withstand temperatures greater than 1400 deg. C and survive blasts of radiation at levels not experienced by any previous spacecraft. The mission's goal is to sample the sun's plasma and magnetic field at the very source of the solar wind.How do ya like them apples?