GPS signal fluctuations associated with high speed flows in the cusp ionosphere

Abstract:

The feature of that strong phase fluctuation with relative weak amplitude scintillation at high latitudes has been reported by many researchers in decades. It is a widely accepted character now especially at auroral region. In the cusp ionosphere, our observations confirm this phenomenon according to plasma flows firstly. To further explore, the statistic study over a 3 year period (2013-2015) from 18:00 UT to 20:00 UT has been carried out. The relations of GPS scintillations to plasma flow are subject to linear distribution. However, the slopes of these two fitted lines are obviously different, the one 0.156 with phase fluctuations more than an order magnitude larger than another one 0.0131 from amplitude scintillations. According to statistical, when those flow velocity goes up to 1 km/s from 0 km/s, phase fluctuations rise to higher than 0.3 rad from lower than 0.1 rad. Within that range of velocity, the amplitude scintillations are always below 0.1. As a possible major explanation for these scintillation manners, the effect of frozen cut-off frequency is directly confirmed by our data. The results will be useful to deeply understand the widely used scintillation indices as well as helpful to establish empirical scintillation model in the polar region.