On the relation between auroral “scintillation” and “phase without amplitude” scintillation: Initial investigations

The ionosphere, being a plasma, affects any radio signal passing through it by introducing a phase advance and a group delay in the signal. Occasionally, due to electron density irregularities in the ionosphere, the radio signal can experience rapid amplitude and phase fluctuations called scintillation. Scintillation can sometimes be intense enough to cause a Global Positioning System (GPS) receiver to lose lock on a signal, thus making it a significant aspect to consider in GPS-based positioning, navigation, and timing systems. Quantitative information about scintillation is usually obtained from parameters called the scintillation indices. The most commonly used GPS scintillation indices are S₄ and σ_φ that quantify scintillation in power and phase of the GPS signal, respectively. Recent studies have shown that at high latitudes, the probability of occurrence of phase scintillation is greater than amplitude scintillation. These events are called “phase without amplitude” scintillation. In this study, the relation between these events and auroral scintillation is analyzed. As an initial step, data from the Canadian High Arctic Ionospheric Network and 10 more GPS stations located in Canada was used simultaneously along with data from 11 Canadian THEMIS all-sky imagers. Preliminary investigations reveal that phase fluctuations associated with aurora can be the main reason behind “phase without amplitude” scintillation. Spectral studies of differential-carrier-phase TEC were also performed to support this hypothesis.