Terrestrial and extraterrestrial plasmas

The starting point for the discussion is some basic problems which have to be solved in plasma physics before a thermonuclear fusion reactor for the production of useful energy can be built. Phenomena of solar, interplanetary, and planetary plasmas can indicate how extraterrrestrial plasmas behave. In connection with thermonuclear fusion, such phenomena are of particular interest which occur in a plasma with the mean free path of the particles large compared to the other relevant scale lengths - in particular, in comparison with the gyro-radii of the particles in a magnetic field. These conditions can be studied very well on extraterrestrial plasmas while they are rather difficult to fulfil in laboratory plasmas. (Auth.)