Effect of nearby supernova explosions on atmospheric ozone

The authors made calculations of the intensity of ionising radiation expected from a supernova event and used the results to calculate the 03 depletion attributable to nitrogen oxide catalysis. This indicated that the 03 depletion, although smaller than estimated in the earlier studies, is still significant and could, due to cosmic rays extend over a very long period of time (103 to 104 years). In calculating the effect of γ-rays the possibility was considered that these are attributable to extragalactic supernovae. The calculations indicated that the occurrence of such an event 10 pc from the Earth would result in an 03 column reduction of 35 to 65% for 1047 to 1048 erg pulses, and that the recovery time of the stratosphere to 95% of normal is about 10 years. Present searches for smaller bursts seem, however, to favour galactic origin, and the energy involved in this case would be insignificant with regard to 03 reduction. The total energy contained in the form of trapped cosmic rays in supernova remnants expanding into the interstellar medium is considered. (UK)