利用GNSS数据结合NeQuick模型优化磁暴期F2层临界频率参数估计

F2层临界频率foF2是高频通信的重要参数,目前获取F2层临界频率(foF2)最有效的手段是电离层测高仪,但磁暴期间电离层自身剧烈变化会造成测高仪foF2数据严重缺失。经验模型如NeQuick虽能给出foF2估计值,但磁暴期精度却不及磁静日水平。本文选取2015年12月19日至2015年12月22日磁暴期中国地壳运动监测网GNSS双频数据进行区域建模并估算出电子总含量(total electron content,TEC),利用实测区域TEC对NeQuick模型有效电离参数Az进行估计,得出NeQuick模型优化后TEC总含量和F2层临界频率foF2,并反演出磁暴期初相,主相及恢复相阶段变化过程。以中国地区台站实测数据作为参考对比,结果表明:GNSS数据优化后的NeQuick模型TEC精度大概提升了20%~40%,foF2的实时精度提升了10%~25%。GNSS优化后NeQuick模型能准确反演出电离层的由正相暴转为负相暴演化过程,而原始模型由于仅依赖于输入的太阳活动水平,只能反映出与磁静日水平相当的日变化趋势值。利用该方法可以有效提高磁暴期TEC和foF2的经验模型的计算精度,特别是弥补磁暴期foF2数据缺失的不足,可以作为磁暴期电离层垂直探测仪的有益补充或者有效参考。

Optimized estimation of foF2 using GNSS data ingestion to NeQuick model during magnetic storm

The critical frequency of F2 is an important parameter for high frequency communications. Ionosonde measured foF2 is an effective way but it would be affected by geomagnetic storm which will even lead to the data missing. NeQuick model could estimate the TEC and foF2.But the accuracy would be degraded during geomagnetic storm. Using the dual frequency GNSS data from the CMONOC(Crustal Movement Observation Network of China)and applying the regional polynomial model, the accurate TEC could be retrieved. Based on the condition that the sum of the squared errors is the minimum, the effective ionized parameter Az could be estimated using the calculated TEC. Using the NeQuick model input by ionized parameter Az, the TEC and foF2 could be retrieved. Using the observations of five ionosonde stations located in different latitudes is in China, the result indicated that the TEC RMS improved 20%~40%, and the foF2 RMS improved 10%~25%. This method could improve the TEC and foF2 accuracy. It showed the benefit of low cost. So it could be considered as the alternative way to the ionosonde observations especially for the foF2 data missing period.