New research helps explain why the solar wind is hotter than expected
(PHYSorg.com Space & Earth)

When a fire extinguisher is opened, the compressed carbon dioxide forms ice crystals around the nozzle, providing a visual example of the physics principle that gases and plasmas cool as they expand. When our sun expels plasma in the form of solar wind, the wind also cools as it expands through space-but not nearly as much as the laws of physics would predict.