Eleven-Year Variation in Polar Ozone and Stratospheric-Ion Chemistry

See allHide authors and affiliations

Science  07 May 1976:
Vol. 192, Issue 4239, pp. 555-557
DOI: 10.1126/science.192.4239.555


A mechanism for producing an 11-year oscillation in ozone over the polar caps is the modulation of galactic cosmic rays by the solar wind. This mechanism has been shown to give the observed phase in ozone oscillations and the correct qualitative dependence on latitude. However, the production of nitrogen atoms from cosmic-ray collisions seems inadequate to account for the ozone amplitude. Negative ions are also produced as a result of cosmic-ray ionization, and negative-ion chemistry may be of importance in the stratosphere. Specifically, NOx may go through a catalytic cycle in much the same fashion as NOx, but with the important distinction that it does not depend on oxygen atoms to complete the cycle. Estimates of the relevant rates of reaction suggest that negative ions may be especially important over the winter polar cap.