[en] A theory of the interaction of a neutral gas with a moving magnetized plasma with particular reference to the direct interaction experiment of Danielsson is presented. It is shown that the velocity given by the equation (1): 1/2 Mn Vsub(c)sup(2) = ephisub(ion) is essentially the relative terminal velocity attained after the interaction is over. On the other hand, the threshold relative velocity required for an active interaction between the plasma and the neutral gas to occur is shown to be given approximately by the equation (2): 1/2 Msub(i)V² = ephisub(ion). For the gases used in the Danielsson experiment (H-plasma and neutral He) Vsub(c)sup((2)) = 2Vsub(c)sup((1)), where Vsub(c)sup((2)) is the value determined from Eq.(2), there is an indication to this effect in the results of the Danielsson experiment. The important observations recorded in the experiments of Danielsson (1970) and of Danielsson and Brenning (1975) are reviewed. Most of these observations are explained on the basis of the present model. (A.K.)