Precipitating relativistic electrons: Their long‐term effect on stratospheric odd nitrogen levels

Abstract

Using electron count rate data at geostationary orbit, daily energy spectra, extending from 30 keV to 15 MeV, have been developed for trapped relativistic electrons at 6.6 R E These spectra have been used to model the flux of these electrons into the atmosphere at 120 km. Energy deposition calculations permit daily sources of HO x and NO y to be calculated at auroral and subauroral latitudes due to relativistic electron precipitation (REP) for the period June 13, 1979, through June 4, 1988. Both short‐term and long‐term source variations are quite large over the period considered. The long‐term variation of the NO y source is found to reach a maximum in late 1984 and early 1985, with significant declines thereafter. Daily Solar Backscattered Ultraviolet (SBUV) O 3 data show a significant response to these precipitation events. Two‐dimensional model calculations have been carried out for the period 1979 to 1990 with REP effects included through June 4, 1988. Results suggest that globally integrated NO y has increased by 35–40% from 1979 to early 1985 with declines thereafter. The largest long‐term increases are found in the lower stratosphere at the high latitudes. Comparisons of Limb Infrared Monitor of the Stratosphere (LIMS), Solar Mesospheric Explorer (SME), Stratospheric Aerosol and Gas Experiment (SAGE), and SAGE II NO 2 data are consistent with these calculations. The results suggest that a significant contribution to the anomalously large and unexplained global O 3 declines between 1979 and 1985 has been made by the catalytic destruction of O 3 by odd nitrogen in the lower stratosphere at mid to high latitudes. The results also provide evidence for a clear and strong linkage between solar variability, the state of the magnetosphere, and the chemical climatological state of the middle and lower atmosphere.