The August 1972 solar proton event and the atmospheric ozone layer

Abstract

OXIDES of nitrogen are generally accepted to be important for regulating the atmospheric ozone content through catalytic reactions first described by Crutzen¹ and Johnston². In the stratosphere, nitric oxide is produced naturally by the reaction of nitrous oxide, emanating from the biosphere, with excited oxygen atoms generated by ozone photolysis at wavelengths shorter than about 310 nm. As Crutzen et al.³ have pointed out, large amounts of nitric oxide may also be produced by high-energy solar protons, mainly at geomagnetic latitudes greater than 60°, and altitudes above about 35 km. The ozone measurements reported here made during an intense solar proton event in August 1972 suggest that NO production rates due to ionising particles are higher than those calculated by Crutzen et al.