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Laboratory for Atmospheric and Space Physics

NOy: solar coupling

September 24, 2012

A significant coupling has been proposed to exist between solar activity, energetic electron precipitation (EEP) from the magnetosphere into the atmosphere followed by NOy formation with its transport to the stratosphere possibly altering stratospheric O3.

The verification of this solar-terrestrial coupling requires three essential findings. (1) Show that precipitating electrons respond to solar forcing, in this case the solar wind. (2) Show that NOy is formed in the mesosphere and the lower thermosphere during electron events. (3) Show that the NOy formed is transported into the stratosphere. Items (1) and (2) have been unequivocally demonstrated to occur using solar wind data from the WIND spacecraft, SAMPEX PET and LICA electron data, and the UARS HALOE NO (nitric oxide) data. Recently, we have used the UARS ISAMS (Improved Stratospheric and Mesospheric Sounder) nighttime NO2 data together with the TIROS SEM (Space Environment Monitor) electron data in a study which illustrates the formation of NO2 (a component of NOy) during electron events and the transport of the NO2 into the stratosphere.

Figure to th left shows NOy formation, both calculated and observed, and the transport into the stratosphere are illustrated for both cases ( postscript version ).

The ISAMS data shows the formation of NO2 near 0.1 mbar (approximately 65 km) during electron events occurring in the northern and southern hemispheres in November 1991 and in May 1992. The NO2 formed is consistent with the NOy formation rate calculated from the electron spectra derived from the electron observations. The subsequent transport of the NO2 into the stratosphere (below 1 mbar) is shown by the ISAMS data, and it extends from the poles to 30 to 40 degrees latitude.

Contributed by Linwood B. Callis, NASA Langley

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