低地磁扰期间海南电离层F2层临界频率的观测与IRI预测结果的对比研究

国际参考电离层模型(IRI)是非常有影响的电离层经验模型之一,利用该模型对我国东亚地区,尤其是海南低纬度地区,进行长期预测的效果尚未研究。通过对一个太阳活动周(2002~2012年)期间海南观测站(19.5°N,109.1°E)数字测高仪DPS-4D观测到的电离层临界频率foF2在低地磁扰动条件下的月中值日变化、季节变化和年变化进行了分析;并与相应的IRI-2012模型预报值进行了对比研究。结果表明:1观测到的foF2存在着明显的冬季异常和半年异常现象,对太阳活动存在着明显的依赖关系;2IRI-2012模型预报值虽给出了海南foF2的基本观测特征,但细节上IRI模型预测值与观测值还是存在着地方时、季节和年度偏差,主要表现为:在太阳活动低年模型存在高估;在太阳下降年期间模型存在低估;在太阳活动较高时期模型存在明显的分季低估,冬、夏季高估;整体上,多数偏差率在±20%以内。偏差率较大的时段主要集中在0500-0800LT,这与以前研究结果基本一致。这些结果对进一步完善IRI模型,尤其是在中国低纬度地区foF2预测参数方面,具有重要的参考价值。

Comparison of ionospheric foF2 observed at Hainan station with IRI-2012 predictions during the low geomagnetic disturbed time

International Reference Ionosphere (IRI) model is one of the most important ionospheric experienced models. But it has not evaluated the ability of using the model to predict the Ionosphere over East Asia, especially over low latitude Hainan region during a very long period yet. In this paper, based on the ionospheric F2 layer critical frequency (foF2) data observed by digisonde DPS-4D at Hainan station (19.5o N, 109.1o E) at nearly quiet time during a solar cycle period from 2002 to 2012, we investigate the diurnal, seasonal and annual variations of the monthly median values of foF2, and compare them with IRI -2012 model predictions. The main results show: 1) the observed foF2 are obvious dependence on solar activity, i.e., they vary with solar activity. Moreover, the winter anomaly and semiannual anomaly occur as well. 2) Though IRI-2012 model results can show the basic features of monthly median foF2 over Hainan, there are in details many deviations on local time, seasonal and annual variations in model predictions and observed ones. They exist on the following aspects: IRI model underestimates in low solar activity and overestimates in the decreasing year of solar activity. While in high solar activity IRI model underestimates in equinox months and overestimates in winter and summer. Most of the deviation percentage rates (R) on the predicting foF2 with observed ones are in ±20%. The larger Rs mainly occur on 0500-0800 LT, which is similar to the previous studies. The current results will be very valuable for further improvement of IRI-2012 in foF2 prediction aspect over Chinese low latitude region.