Evidence has accumulated for the past two decades demonstrating a correlation between Earth transits of the heliospheric current sheet (HCS) and changes in winter tropospheric vorticity. These correlations persisted for a few years following the Agung and El Chich¿n volcanic eruptions, but were significantly weaker at other times. This suggests that the missing link in a physical mechanism explaining the correlation may involve volcanic aerosols and their effect on cloud microphysics, via atmospheric electricity. An analysis of 500-mbar northern hemispheric vorticity for the 1991-1994 winter periods following the Pinatubo eruption shows a similar correlation between tropospheric vorticity and Earth transits of the HCS, supporting the previous interpretation. ¿ American Geophysical Union 1996