ИСТИНА

Total electron fluctuations at high latitudes are caused presence in the ionosphere of different scale irregularities. The TEC fluctuations are occurred as phase fluctuations GPS/GLONASS signals. The most intense ionospheric irregularities have been observed during ionospheric storms and depend on latitude, solar geomagnetic activity, and local time. Irregularities are classified according with subauroral, auroral, cusp and polar cap regions. In the auroral region, phase fluctuations are usually observed during periods of auroral disturbances near the local magnetic midnight and are closely associated with the dynamics of the auroral oval. The ionospheric irregularities also exist a subauroral region equatorward of the MIT. Strong TEC fluctuations can complicate phase ambiguity resolution and to increase the number of undetected and uncorrected cycle slips and loss of signal lock in GPS navigation and positioning errors. Early analysis of TEC fluctuations was done mainly for strong magnetic storms. In this work we present features of the TEC fluctuations occurrence and positioning errors for the moderate geomagnetic storm of 4 November 2021.