Ionospheric scintillation

Magnetic Field-Aligned Irregularities (FAI) with scale sizes from meters to tens of kilometres are generated by different plasma instabilities. These FAIs are generally most severe at high and low latitudes, but may occur at any place or time during the entire solar cycle. These irregularities may disrupt Very High Frequency (VHF), Ultra High Frequency (UHF), and Global Navigation Satellite Systems (GNSS) at L-band frequencies. The amplitude and phase scintillations of the radio wave front cause degraded performance for Global Navigation Satellite System (GNSS) receivers and even loss of satellite lock and navigation solution.

The generalized view is that high latitude scintillations are created in density gradients associated with polar cap patches. Polar cap patches are defined as 100 km scale regions with F-region plasma densities 2–10 times larger than the background density in the polar cap, and the Gradient Drift Instability (GDI) is considered as the dominant instability mode. However, Prikryl et al. (2011) found evidence that cusp irregularities are driven by polar cap patches while night-side auroral scintillations seem to be driven by energetic electron precipitation. Carlson (2012) pointed out the need to differentiate between high-density polar cap patches (solar-EUV source) and low-density patches (produced by auroral particle precipitation).

This research will be investigating the different signatures of scintillations generated by high density polar cap patches and low density patches associated with particle precipitation. The research will also investigate the underlying mechanisms (plasma instabilities) and will address which of the two mechanisms: Gradient Drift Instability (GDI) or strong flow shears (i.e. shear driven instability) is the dominant mechanism responsible for high-latitude ionospheric scintillation.