Changes in solar EUV produced conductivities during geomagnetic storms: seasonal differences

Ionospheric conductivities are a key part of magnetosphere-ionosphere-thermosphere coupling. Although particle precipitation creates much of the conductivity in the region where the field-aligned currents close in the ionosphere, solar EUV produced conductivities can play a significant role. Models of this coupling assume that conductivities produced by particle precipitation vary as geomagnetic activity varies, but that solar EUV produced conductivities vary only with changes in solar radiation and with solar zenith angle. In a recent presentation we demonstrated that these solar induced conductivities can be reduced considerably during a geomagnetic storm as the result of a build up of NO and the consequent change in ion composition. In this presentation we extend this work to look at how seasonal effects impact these conductivity changes using a CMIT run for the May 1997 geomagnetic storm. During this storm decreases in solar EUV produced conductivity are noticeable in both hemispheres, but the strength of the effect is the result of a complex interaction between NO densities, ion densities and cross sections for collisions between ions and neutrals.