Improving NeQuick Model Connection between the Topside Ionosphere and Plasmasphere

The dynamics of the ionosphere and plasmasphere are strongly coupled: the ionosphere refills the plasmasphere on the dayside, while plasmaspheric particles help sustain the ionosphere at night. The NeQuick model, for instance, extrapolates ionospheric dynamics into the plasmasphere using parameters anchored in the F2-layer. However, despite these strong coupling processes, empirical models can benefit from treating these "spheres" as distinct regions. In this work, we propose a new formulation for the NeQuick model, which considers the plasmasphere as a layer entirely independent of ionospheric parameters. This adjustment led to significant improvements, partially resolving previous model underestimations and preserving a more realistic plasmaspheric structure along geomagnetic field lines. Based on extensive validation using data from 2008 to 2024, the revised NeQuick model demonstrated improvements ranging from 28% to 40%, depending on solar activity. These results suggest that modeling the ionosphere and plasmasphere as independent layers is a viable solution for improving both accuracy and the representation of plasma structures.