Magnetic reconnection heating of cusp and polar thermosphere

Magnetic reconnection has already been established as the primary production mechanism for most polar cap patches. A first principles examination of this process has led to prediction of other polar cap phenomena which have also been confirmed. Here we extend a first principles examination of the process, within the context of its key observed morphological properties, to evaluate consequences to be expected for thermospheric temperature and density perturbations. We conclude this process must inevitably lead to ridges of upper atmospheric density enhancements in the range of ~10% to doubling near and above 400 km altitude. We emphasize the critical dependence on velocity shear and particle flux spectra, which control where the consequences will be strong or weak. We highlight the morphology of velocity shears ubiquitous in the dayside polar cap, and by application of first principles further note those observed morphological properties which must be key to meaningful modeling of the impact on thermospheric densities and drag.