Galactic radiation belts

Abstract

Several decades of observations have failed to resolve the problem of the interpretation of extended extragalactic radio sources^1,2. Most current models invoke the ejection of pairs of plasmoids or relativistic electron beams from the parent elliptical galaxy by various mechanisms^3–5. As these theories generally predict the relative orientations of the rotation, magnetic and radio source axes, the measurement of position angles provides one test of the proposed models^6,7. However, position angle studies^6–11 have produced ambiguous and sample-dependent results. While recent analyses^6,7 indicate a preference for radio source alignment along the inferred rotation axes of the optical counterparts, other investigations found random distributions of position angle or bimodal distributions with peaks separated by ∼90° (refs 8, 10). One alternative interpretation of extragalactic radio sources that has received little previous consideration, and is considered herein, concerns the possibility that the emission arises from belts of trapped electrons encircling the parent galaxy in the same manner as the Van Allen belts encircle the Earth. This idea seems to have been dismissed primarily because of the absence of ring-shaped or toroidal emission patterns in the radio observations¹². The morphology of synchrotron emission patterns from these hypothetical structures, however, has never been investigated in detail.