Altitude Dependence of Quasi‐Static Potential Drop: The Effect of Ionospheric Protons

Abstract Using an improved kinetic model that incorporates cold ionospheric protons and oxygen ions, we investigate the factors controlling the altitude range of the auroral acceleration region (AAR). In this model, parallel electric fields are generated via Dispersive Alfven Wave‐ Modified electron Acoustic Wave (DAW‐MEAW) coupling and sustained by the thermal pressure of hot electrons that displace cold electrons. Our results demonstrate that the AAR lower boundary descends with increasing potential drop or hot electron density, but ascends with increasing hot electron temperature. The AAR altitude is also modulated by ionospheric plasma conditions: lower ionospheric temperature and density shift the boundary downward, consistent with Auroral Kilometric Radiation observations showing a lower AAR in winter. The inclusion of cold ionospheric protons amplifies this altitudinal shift for a given potential drop, due to their larger scale height compared to oxygen ions.