SOLAR ATMOSPHERIC COUPLING BY ELECTRONS (SOLACE) 1 - EFFECTS OF THE MAY 12, 1997 SOLAR EVENT ON THE MIDDLE ATMOSPHERE

An analysis is carried out of the effects on middle atmospheric NOy an d O-3 of a coronal mass ejection (CME) event which occurred on May 12, 1997, and which is coupled with observed solar wind fluctuations. Obs ervations of electron fluxes by instruments aboard the SAMPEX and NOAA 12 satellites indicate large enhancements of magnetospheric electron fluxes occurring with the arrival of the high-speed solar wind. Calcul ations suggest that significant formation rates of NOy should occur in the mesosphere and the lower thermosphere at mid to high latitudes. H alogen Occultation Experiment (HALOE) NO observations reveal increases of more than an order of magnitude between 85 and 120 km in both hemi spheres within 1-2 days after the electron flux increases. Two dimensi onal chemical transport simulations were carried out to assess the fat e of the NO, increases. Northern hemispheric increases were lost to ph otochemical destruction shortly after the event ended. Southern hemisp heric increases were transported in part into the stratosphere by adve ctive descent. By October 1997, high-latitude NOy increases of 20-40% were calculated near 25 km leading to O-3 reductions of up to approxim ate to 20% when compared to a simulation with no electron precipitatio n. A solar atmospheric coupling by electrons precipitating from the ou ter trapping and auroral regions of the magnetosphere, and which affec ts middle atmospheric NO, is clearly demonstrated by the observations alone.