The Plasmasphere During Geomagnetic Storms

Geomagnetic storms cause significant impacts on the magnetosphere. Brightened auroras may last for a much longer time and often extend to lower latitudes, in comparison to a typical substorm event. However, more spectacular consequences of storms are seen in the magnetosphere a few Earth radii away from the Earth, resulting in an intensification of the energy flux of the trapped population, which consequently leads to a geomagnetic response on the global scale. Ultimately, electric fields originating from the coupling between the solar wind and the magnetosphere results in the inward displacement of the boundary between open and closed streamlines, causing inward injection of hot tenuous plasma from the outer magnetosphere and erosion of cool dense plasmaspheric plasma, which can be imaged by satellites such as IMAGE. The Earth’s plasmasphere shows great variability during intervals of intense geomagnetic activity.
We investigate observations of the plasmaspheric helium ion budget and of the aurora from IMAGE EUV and FUV, respectively, combined with measurements from SuperDARN to better understand and quantify the changes in the Earth's outer radiation belt during strong storms. We show the results for two major storms on August 2000 and April 2001 with the best possible image coverage. Correlations existing between different parameters relating the trapped particles in the plasmasphere, the aurora and magnetic reconnection are deduced. We identify correlations amongst the solar wind velocity, the magnetic field, the open magnetic flux and the Dst index. We investigate more possible correlations with other geomagnetic indices. The correlation is significantly higher when we restrict the storm events to the most active intervals. We search for a relation with particle fluxes measured at geosynchronous orbit by the GOES satellite.