We review our understanding of ionized plasma and neutral gas coupling in the weakly ionized, stratified, electromagnetically-permeated regions of the Suns chromosphere and Earths ionosphere/thermosphere. Using representative models for each environm
ent we derive fundamental descriptions of the coupling of the constituent parts to each other and to the electric and magnetic fields, and we examine the variation in magnetization of the ionized component. Using these descriptions we compare related phenomena in the two environments, and discuss electric currents, energy transfer and dissipation. We present a coupled theoretical and numerical study of plasma instabilities in the two environments that serves as an example of how the chromospheric and ionospheric communities can further collaborate. We also suggest future collaborative studies that will help improve our understanding of these two different atmospheres which share many similarities, but have large disparities in key quantities.
