Cosmic linea accelerators

The existence of field-aligned potential drops is related to unstable field-aligned currents. It is postulated that the region of instability, once set up, can propagate spontaneously into the interior of the current circuit, like a fracture in a stressed solid body, and thus achieve a fast magnetic stress relief. Most of the released magnetic energy is converted into kinetic energy of field-aligned particle beams. Parallel voltage and energy flux depend on the primary magnetic stress, the propagation properties of shear Alfven-waves, and the treshold for current instability. Numerical examples for te efficiency of such an acceleration process are given for three cosmical situations. (author). 18 refs.; 6 figs