A statistical study on L-band ionospheric amplitude scintillation in Shenzhen during 2011‒2016

Abstract

Based on ionospheric amplitude scintillation observation data from the Shenzhen Ionospheric Scintillation Monitor from 2011 to 2016, the local time, seasonal solar activity, and spatial distribution of amplitude scintillation of various strength levels and its effect on GPS observation (manifestation in loss of lock of L1 and L2 signals) are studied. The results show that ionospheric amplitude scintillation in Shenzhen mainly occurred after sunset until midnight (19:00–02:00 LT) and the scintillation occurrence for various S 4 intervals (weak, moderate, and strong scintillation) exhibited negligible differences. The peak time of weak scintillation occurrence was about 21:00–22:00 LT, and its distribution to local time seems symmetrical. However, the peak time of moderate and strong scintillation occurrence was around 20:00–21:00 LT and its distribution to local time was asymmetrical. In addition, the loss of lock of GPS L1 and L2 signals derived from GPS observations at the HKSL GPS station near Shenzhen were also used for comparison with the ionospheric amplitude scintillation. It was found that the local time variation of the loss of lock was very similar to the occurrence of strong ionospheric scintillation. Stronger intensities of amplitude scintillation showed better correlation between amplitude scintillation and loss of lock. The seasonal variation of Shenzhen ionospheric scintillation was similar to that in previous studies in this area. In other words, the scintillation mainly occurred in the equinox months and rarely occurred in the winter and summer months, which coincides with the seasonal distribution characteristics in the Asia–Pacific sector. In solar cycle variation, ionospheric amplitude scintillation is dependent on solar activity. From 2011, the scintillation occurrence increased gradually and reached a peak in the spring of 2014. It then dropped quickly until 2016, when scintillation rarely occurred. This variation shows a good positive correlation with the sunspot number. Considering the scintillation data for equinox months only, the correlation coefficient between scintillation occurrence and sunspot number can reach more than 0.6. In addition, considering scintillation occurrence in various S4 intervals, except 2014, the occurrence satisfies a weak > moderate > strong trend. However, in 2014, strong scintillation occurrence is noticeably higher than weak scintillation. As for the spatial distribution of scintillation, scintillation occurs more frequently in the southern part of Shenzhen. With the increase in scintillation intensity, the azimuthal distribution of scintillation becomes narrow. The weak-amplitude scintillation mainly occurs between the azimuth angles of 100° and 250°, whereas the strong-amplitude scintillation mainly occurs between the azimuth angles of 180° and 200°. In addition, the loss of lock of GPS L1 and L2 signals also exhibits obvious directional properties, mainly occurring between azimuths 170° and 180°.