Interhemispheric asymmetry of ionospheric conductance and neutral dynamics

Abstract:

Interhemispheric asymmetry has been identified in a number of studies with hemispheric power (HP) and convection pattern between the two hemispheres. The asymmetry of geomagnetic forcing in the two hemispheres can strongly influence the magnetosphere–ionosphere–thermosphere coupling process. Subsequently the responses of the thermospheric dynamics and density to geomagnetic storms between the two hemispheres were reported to be different as well. In our study, the asymmetry has been examined in both ionosphere and thermosphere. First, the Pedersen conductance at high latitudes has been estimated from the electron density profiles (EDPs) of the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites observations during 2008 to 2011. The ratio of the height-integrated Pedersen conductivities between E (100–150 km) and F (150–600 km) regions has been calculated. The analysis shows that the ratio reaches maximum in local winter and minimum in local summer, but the variation of the ratio from local summer to local winter in the southern hemisphere is larger than that in the northern hemisphere, which indicates that the energy partition between the E and F regions in the southern hemisphere changes more significantly than that in the northern hemisphere. Secondly, the seasonal variation of F region neutral wind from the mid-latitude conjugate Fabry-Perot interferometer (FPI) observations has been studied. The neutral winds from Palmer station (64^◦S, 64^◦W) have been compared with those from the geomagnetic conjugate location, Millstone Hill (MH). At equinox, the local
time variation of neutral wind shows a very good conjugacy between these two locations. But at June solstice, the similarity in the zonal wind becomes less clear. The annual variation of daily average neutral wind from Palmer and MH has also been compared. The annual variation of neutral wind, especially the zonal component, is much less symmetric between the two sites than the local time variation. The empirical horizontal wind model shows a good agreement with the observations in both local time and annual variations. The results of this study will greatly advance your understanding of the physical processes and improve our capability to describe the atmosphere response to external drivers.