Monitoring and Modeling of Ionosphere Irregularities Caused By Space Weather Activity on the Base of GNSS Measurements

Abstract:

The ionosphere plays an important role in GNSS applications because it influences on the radio wave propagation through out. The ionosphere delay is the biggest error source for satellite navigation systems, but it can be directly measured and mitigated with using dual frequency GNSS receivers. However GNSS signal fading due to electron density gradients and irregularities in the ionosphere can decrease the operational availability of navigation system. The intensity of such irregularities on high and mid latitudes essentially rises during space weather events. For monitoring of the ionospheric irregularities data collected from all available permanent GNSS stations in the Northern Hemisphere are processed and analyzed. Here we used parameters ROT (rate of GPS TEC change) and ROTI (index of ROT) to study the occurrence of TEC fluctuations. ROTI maps are constructed with the grid of 2 deg x 2 deg resolution as a function of the magnetic local time and corrected magnetic latitude. The ROTI maps allow to estimate the overall fluctuation activity and auroral oval evolutions, in general the ROTI values are corresponded to the probability of GPS signals phase fluctuations. There were developed several models in order to represent ionospheric fluctuations and scintillation activity under different geophysical conditions, but they were calibrated with data sets, that did not include GNSS derived data. It is very actual to develop empirical model based on GNSS derived measurements which can represent strong fluctuations of the ionosphere plasma density at high latitudes. The measurements provided by the existing permanent GNSS networks accumulated in order to develop the empirical model of ionospheric irregularities over the Northern hemisphere. As initial data the daily dependences of the ROTI index are used as a function of geomagnetic Local Time on the specific grid. With ROTI index maps it was determined the irregularities oval border and averaging parameter – semi-hemisphere fluctuation index. It was investigated the statistical and correlation dependences between Kp geomagnetic index and parameters that characterized the ionosphere irregularities activity for period of 2010 – 2014 years. The results of observations for specific events, modeling and its validation will be presented.