Diffusive acceleration of electrons in supernova 1987A

The reappearance of radio emission from SN 1987A in July 1990 is discussed. We propose a model involving synchrotron radiation from electrons which are accelerated by the expanding supernova shock wave. From the observed delay in which the switch‐on between 843 MHz and 4.8 GHz we derive the mean free path of the electrons and the time at which the acceleration process must have started, presumably as a result of the shock encountering a density jump in the circumstellar material.