The ionosphere-earth current density (Jz) in the global atmospheric electric circuit at any location is due to (1) the varying overhead ionospheric potential, and (2) the varying ionosphere-earth column resistance, which consists of a tropospheric component (Rt) and a middle atmosphere (stratosphere and mesosphere) component (Rm) in series. The ionospheric potential is modulated globally by changes in thunderstorm output, and within the polar caps by the IMF By component, and close to the auroral electrojets by their intensity. Rt and Rm are modulated by increasing amounts at increasing geomagnetic latitudes by galactic cosmic ray flux variations. Rm is modulated by solar proton events in the polar cap and by relativistic electron precipitation at sub-auroral latitudes. The energetic particle effects on Rt and Rm are enhanced by the presence of stratospheric aerosols, which lower the conductivity from the clear-air values so that the regions above 25 km, where relativistic electrons and solar protons ionize, constitute non–negligible components in Rm. The region centered on 15 km where the cosmic ray ionization is greatest requires less stratospheric aerosol content for significant effects. Thus there are longer-lasting effects on the total column resistance and Jz with cosmic ray flux changes than with relativistic electrons following volcanic eruptions. All these modulations in Jz produce corresponding changes in clouds and atmospheric dynamics due to electric charge modulation of aerosol scavenging. Observations demonstrating these influences will be reviewed.
Mode of presentation: oral (Need to be confirmed by the SOC)