Daria Kotova

Describing the current ionospheric conditions is crucial to solving problems of radio communication, radar, and navigation. Techniques to update ionospheric models using current measurements found a wide application to improve the ionosphere description. We present the results of updating the NeQuick and IRI-Plas empirical ionosphere models using the slant total electron content observed by ground-based GPS/GLONASS receivers. The updating method is based on calculating the effective value of the solar activity index, which allows minimizing the discrepancy between the measured and the modelcalculated slant TEC. We estimated the updating efficiency based on the foF2 observational data obtained by ionosonde measurements. We calculated the data for 4 stations: Irkutsk, Norilsk, Kaliningrad, and Sodankylä. We analyzed 4 days in 2014: March 22, June 22, September 22, and December 18. We found that, in some cases, upon updating, the IRI-Plas underestimates the foF2, whereas NeQuick, on the contrary, overestimates it. We found a seasonal dependence of the updating efficiency of the ionosphere model using slant TEC. Possible causes of this dependence might be associated with the seasonal dependence of the correctness of model’s reproduction of the latitude–longitude TEC distribution. In general, we found the low level of the updating efficiency of the foF2 using slant TEC. This can be mainly explained by the fact that the models describe the electron density vertical profile and ionospheric slab thickness incorrectly

Ionospheric irregularities are often the cause of GNSS precise positioning errors, as well as disruption of radio communications in the HF range. The reason for the occurrence of these irregularities can be various non-stationary processes in the near-Earth space plasma that depend on the response of the ionosphere to the variations in the near Earth space. Therefore, the study of ionospheric irregularities is an urgent scientific and applied problem. In this study we use a global product based on the Swarm satellite measurements that characterizes ionospheric irregularities and fluctuations. The IPIR (Ionospheric Plasma IRregularities product) provides characteristics of plasma density structures in the ionosphere, of plasma irregularities in terms of their amplitudes, gradients and spatial scales and assigns them to geomagnetic regions and consequently to predominant plasma processes. It also provides indication, in the form of a numerical value index, on their severity for the integrity of trans-ionospheric radio signals and hence the accuracy of GNSS precise positioning. In this work we made validations of the IPIR product against the ground-based measurements, focusing on GPS TEC and scintillation data in low latitudes regions.

Ionospheric phenomena as a response to geomagnetic activity can be different at both hemispheres, in particular at high latitudes, due to the structure of the ionosphere, orientation of the interplanetary magnetic field and structure of the Earth magnetic field. This may have implications on large scale modeling and space weather forecasting. To understand these aspects, a significant number of studies which include both hemispheres are required. In order to study the asymmetry between the northern and southern hemispheres at high latitudes, we employ the GNSS TEC and scintillation monitors. We use data from a GNSS receiver at Troll station in Antarctica together with corresponding datasets from the northern hemisphere. We carry out detailed study of several representative events for different geomagnetic conditions. We characterize the GPS phase scintillations in the context of interhemispheric asymmetries, and also using other supportive ground based and satellite observations. This is the first study with data from the recently established ionospheric observatory at Troll station in Antarctica. It also forms a ground for more statistical study of interhemispheric asymmetries, where the first results are also shown.