Current-carrying beams in astrophysics: models for double radio sources and jets

If beams of particles originate in corotating magnetospheres, they may carry currents far into distant galactic and extragalactic regions. High-current beams can be more stable than beams without current, since they can be insulated from surrounding plasma by magnetic self-fields. Beams with both azimuthal and axial currents can have very low self-forces acting on the particles, i.e. J × B is minimized, and thus enjoy long synchrotron lifetimes. We show that these spinning beams may be stable if the long-wavelength modes are suppressed by the inertia of a surrounding plasma sheath. Treating beams by a circuit analogy implies that Ohmic dissipation can occur at the tips of the beams, re-accelerating particles, and this may explain the high energies in double radio sources. Jets could be relatively unstable self-pinched beams which are short-lived. In general, adding currents introduces many new physical aspects to the beaming phenomena. We explore some applications to double radio sources and jets.