Current loop models for the circumstellar matter in SN 1987A

Some properties of current-loop models are explored, and some implications are discussed. The elliptical ring observed to be centered on the supernova can be interpreted as light from ions trapped in the magnetic field of a circular current loop. The current is 1.5×10 ¹² A for a model where gravitational force on 0.03 solar masses of trapped matter balances the electrodynamic expansion of the loop. The magnetic energy of the loop is 2×10⁴¹ erg. Consideration of the magnetized clouds in the solar wind as an analogous source for such a loop leads to the conclusion that the loop formed over the lifetime of the progenitor star