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The role of the magnetic field in the confinement or compression of interstellar gas clouds is reconsidered. The virial theorem for an isolated magnetized cloud in the presence of distant magnetic sources is reformulated in terms of moments of the internal and external currents, and an equilibrium condition is derived. This condition is applied to the interaction between isolated clouds for the simple- and artificial-case in which the field of each cloud is a dipole. With the simplest of statistical assumptions, the probability of any given cloud being compressed is calculated as ~ 10%, the magnetic field acting as a medium which transmits the kinetic pressure between clouds. Even when compression occurs the magnetic pressure \(\frac{1}{2}B^2\) may decrease on leaving the cloud surface.

We consider the Alfven-Arrhenius fall-down mechanism and describe an approximate model for the infall, capture and distribution of dust particles on a given magnetic field line and their possible neutralization at the ‘\(\frac{2} {3}\)’ points, the points at which the field aligned components of the gravitational and centrifugal forces are equal and opposite. We find that a small fraction ( \frac{{10^{ - 3} }} {{r_{gu} T_{\text{eV}} }}$$ (rgµ = radius of a grain in microns, T = plasma temperature in eV), then the dust particles will lose their charge, decouple from the field line and follow Keplerian orbits in accordance with the Alfven-Arrhenius mechanism.