我国低纬电离层闪烁和周跳的统计特征比较

本文利用位于我国中南部电离层闪烁监测台网2012年至2015年的观测数据，比较分析了GPS（Global Positioning System）信号闪烁与周跳的统计特征以及太阳活动和地磁扰动对闪烁与周跳的影响.结果表明，闪烁活动与周跳出现随地方时、月份、太阳活动和地磁扰动变化的统计特征类似，且周跳出现的可能性随S4指数增高显著增大，说明闪烁与周跳存在密切的关联，是引起周跳的一种重要因素.一天之中，闪烁和周跳主要出现在日落后至黎明前，午夜前出现最频繁，白天仅偶尔出现.在赤道异常峰及其邻近区域，一年之中，闪烁和周跳主要出现在春秋季，春季闪烁活动和周跳出现明显比秋季频繁，呈现春秋不对称性，冬夏季节闪烁和周跳都很少出现.闪烁活动与周跳出现的逐年变化显著依赖太阳活动水平，随太阳活动水平升高而增强，而地磁扰动与闪烁活动与周跳出现呈负相关，地磁扰动对闪烁活动与周跳出现整体上起抑制作用.平均而言，越靠近磁赤道的台站闪烁活动越频繁，随纬度升高，闪烁活动频次逐渐降低，且闪烁活动的开始时间随纬度升高而滞后，暗示引起GPS信号闪烁的电离层不规则结构主要起源于磁赤道区.此外，分析还发现，闪烁活动与周跳出现的空域有相当好的一致性，主要分布在观测点上空仰角55°以下、方位角150°~240°的空域内.

A comparison of statistical features of ionospheric scintillations and cycle slips in the mid-south region of China

In this paper, the statistical features of scintillations and cycle slips of GPS (Global Positioning System) signals, as well as the effects of solar activity and geomagnetic activity on scintillations and cycle slips have been analyzed and compared on the basis of the observations from a scintillation observation network in the mid-south region of China during 2012-2015.The statistical features include the diurnal variation, monthly variation and spatial distribution of occurrence of scintillations and cycle slips and dependence of occurring probability of cycle slips on the scintillation intensity.
The data used in this paper come from six observation stations which are Sanya (109.58°E, 18.28°N, magnetic latitude 8.49°N), Hongkong (114.21°E, 22.42°N, 12.66°N), Nanning (108.23°E, 22.84°N, 13.08°N), Guilin (110.33°E, 25.29°N, 15.48°N), Ganzhou (114.92°E, 25.84°N, 16.07°N) and Wuhan (114.36°E, 30.54°N, 20.74°N). The data with elevation angles less than 35° were removed to eliminate non-ionospheric effects such as multipath and only the scintillation activities with S4 greater or equal to 0.2 and lasting at least 10 minutes were taken into account as a scintillation event.
The analysis results show that scintillations and cycle slips occur mainly during the night, most frequently before midnight and seldom in the daytime. It is found that scintillations and cycle slips occur mainly in equinox months but seldom in solstice months at the ionization anomaly crest and its adjacent regions, and an equinoctial asymmetry that scintillations and cycle slips occur more frequently in Spring than in Autumn is also found.The occurrence of scintillations and cycle slips shows a strong dependence on the solar activity, it increases as the solar activity increases. However, the occurrence of scintillations and cycle slips shows a negative correlation with geomagnetic activity. The geomagnetic disturbances inhibit scintillations and cycle slips as a whole. On average, the closer to the magnetic equator, the more frequently and the earlier scintillations occur, indicating that the scintillations are caused by ionospheric irregularities which originate at the magnetic equator. In addition, there is a good consistency between the spatial distributions of scintillations and cycle slips. They mainly occur in the area with elevation angle less than 55° and azimuth angle between 150° and 240°.
It is found that the variation features of cycle slip occurrence with local time, month, solar activity and geomagnetic activity are very similar to those of scintillation occurrence, and the occurring probability of cycle slip increases as the S4 index increases. It can be concluded that cycle slips are closely related to scintillations and scintillations are a key factor which can cause cycle slips.