NOy formed by precipitating electron events in 1991 and 1992: Descent into the stratosphere as observed by ISAMS

NOAA 12 precipitating electron data has been examined together with ISAMS observations of nighttime NO2 during electron events in November 1991 and May 1992. Energy deposition calculations suggest the significant formation of NOy during these events near 0.1 mbar and for 60°–80°latitude. ISAMS confirms increases of NO2 from zonally averaged values of ≈1–5 ppbv prior to the events to values in excess of 30–40 ppbv with local maxima in excess of 140 ppbv. The increases occur within 2–3 days and are generally consistent with the calculated NOy formation rates due precipitating electrons. ISAMS data indicate the subsequent transport of the NO2 into the stratosphere affecting NO2 mixing ratios below 1 mbar and down to latitudes of ≈30°to 40°in both hemispheres.