GNSS Scintillations in the Cusp, and the Role of Precipitating Particle
Energy Fluxes
Abstract
Using a large dataset of ground-based GNSS scintillation observations
coupled with in-situ particle detector data, we perform a statistical
analysis of both the input energy flux from precipitating particles, and
the observed prevalence of density irregularities in the northern
hemisphere cusp. By examining geomagnetic activity trends in the two
databases, we conclude that the occurrence of irregularities in the cusp
grows increasingly likely during storm-time, whereas the precipitating
particle energy flux does not. We thus find a weak or nonexistent
statistical link between geomagnetic activity and precipitating particle
energy flux in the cusp. This is a result of a documented tendency for
the cusp energy flux to maximize during northward IMF, when density
irregularities tend not to be widespread. Their number clearly maximizes
during southward IMF. At any rate, even though ionization and subsequent
density gradients directly caused by soft electron precipitation in the
cusp are not to be ignored for the trigger of irregularities, our
results point to the need to scrutinize additional physical processes
for the creation of irregularities causing scintillations in and around
the cusp. While numerous phenomena known to cause density irregularities
have been identified and described, there is a need for a systematic
evaluation of the conditions under which the various destabilizing
mechanisms become important and how they sculpt the observed ionospheric
‘irregularity landscape’. As such, we call for a quantitative assessment
of the role of particle precipitation in the cusp, given that other
factors contribute to the production of irregularities in a major way.