Solar plages and the vorticity of the Earth's atmosphere

THREE superimposed epoch (SPE) analyses of the vorticity area index (VAI) at 500 mbar were carried out using the following definitions of the zero days: (1) the central meridian passage (CMP) of very active solar plages (Fig. 1 a ); (2) the occurrence of peak values of the 10.7 cm solar radio flux (Fig. 1 b ); and (3) the CMP of active solar plages also accompanied at CMP by sharp rises in 10.7 cm solar radio noise (Fig. 1 c ). All three SPE analyses show a sustained rise in VAI several days before the zero day continuing through the zero day, followed by a sustained minimum in VAI several days after the zero day. All three criteria for the zero date give results that are more clear cut than our earlier ones involving simply the occurrence of large solar flares, irrespective of their location on the apparent solar disk. The results lead us to conclude that the location on the solar disk of very active plages plays an important part in determining their meteorological influence. We speculate here that the initial rise in VAI is caused by enhanced electromagnetic radiation associated with the solar activity, and that the decrease some days later is the result of the geomagnetic storm particle emission that generally follows the zero date.