【作者】 苏洋；

【导师】 黄际英； 张北辰；

【作者基本信息】 西安电子科技大学 ， 无线电物理， 2009， 硕士

【摘要】 我国南极中山站和北极Longyearbean的Svalbard站构成地磁共轭,利用国际极地年(IPY,2007-2008)期间数据共享的便利条件,通过对比分析南北半球共轭台站的电离层F层特性的异同,有利于了解极区电离层F层的变化特性及其形成机理。进一步将南极中山站测高仪观测数据以及北极Svalbard站的非相干散射雷达观测数据与最新的国际参考电离层模型IRI-2007进行比较,能够更好的考察IRI-2007对极区电离层的预测情况,以便为进一步改善模型在极区预测发挥建设性作用。本文首先处理了太阳活动低年(2007年)南北两极地磁共轭的中山站DPS-4测高仪观测数据与北极EISCAT-Svalbard雷达观测数据,分析两个台站不同季节电离层F层临界频率(foF2)和峰值高度(hmF2)日变化特性,探讨其共同形成机理。然后进一步利用与最新的国际参考电离层模型IRI-2007预测和观测结果对比分析,考察国际参考电离层在极隙区电离层的适用情况。本文南北地磁共轭的两站观测与IRI模式对比结果表明,IRI模型应用在极区还需进一步改善,并给出了建议。论文的主要研究工作与结果归纳如下:1.南北极电离层F层季节日变化特性研究对于foF2,中山站秋季和Svalbard站春季季节都有明显的磁中午现象出现,且两分季日变化幅度较其它季节大。夏季日变化趋势都比较平缓,日变化幅度较小。冬季曲线都出现双峰结构,但中山站在磁中午附近出现明显主峰,次峰位于17:00MLT附近,且明显小于主峰值;Svalbard站在磁中午附近无峰值出现,两峰值分别位于08:00MLT和18:00MLT附近,且数值大小接近。中山站冬季foF2大小整体比Svalbard站foF2大,与太阳的10.7厘米射电通量(F10.7)大小无关。这说明中山站冬季主峰与较低纬度受太阳电离的高密度等离子体经过极隙区有关,而Svalbard站F层电离层主要受极光粒子沉降作用。对于hmF2,两分季节日变化具有不对称的“W”形状特点,日变化幅度都比较大。夏季日变化幅度都相对较小,曲线比较平缓。较其它季节,无论在变化趋势还是数值大小上,夏季两站hmF2都非常相似。冬季日变化较为平缓。中山站hmF2平均高度要比Svalbard站hmF2平均高度高。2.南北极观测与国际参考电离层对比研究夏季foF2无论中山站还是与其地磁共轭Svalbard站IRI模式预测与观测符合较其它季节要好。这可能是因为IRI模式日变化特性主要基于中低纬度观测结果,较好的考虑了考虑太阳光辐射电离的影响,而两站夏季由于太阳光辐射电离占主导作用。冬季中山站与Svalbard站观测与IRI模式相对偏离很大,IRI模式无法反映出午后峰值的变化。这是由于两站在冬季太阳全天都处于地平线以下,太阳光辐射影响不明显,极光粒子沉降在两分季节和冬季对F层的影响IRI模式未能很好地体现。本文结果还显示,IRI预测的hmF2普遍要比实际观测大。3.改善IRI模型在极区适用情况的建议IRI模型需要单独的模块描述极区极光粒子沉降和极区等离子体对流共同作用下的极区电离层经验模型。IRI作为依赖观测数据的经验模型,需要增加极区的观测台站,为IRI模型的进一步完善提供长期可靠的观测依据。更多还原

【Abstract】 Based on the good geographic locations of magnetic conjugate between Chinese Zhongshan Station in Antarctic and Svalbard Station in Arctic, with the convenient share of International Polar Year (IPY, 2007-2008) radar data, the characteristics of F layer ionosphere in both hemispheres are compared. It is helpful to understand ionosphere structure and formation mechanism. Further more, the data obtained from both DPS in Zhongshan and incoherent scatter radar in Svalbard are compared with that predicted by the latest International Reference Ionosphere model, IRI-2007, which can evaluate IRI-2007’s forecasting capability so as to help improve its accuracy in polar regions.Firstly, This paper analyzes the changing characteristics of ionosphere in Zhongshan and Svarbard by using the respective observation data. The diurnal variation of F2 peak parameters foF2 and hmF2 is analyzed and their formation mechanism is discussed. The IRI-2007 forecasting results are compared with the observation results, and IRI model condition in polar gap ionosphere is introduced. In this paper, the North and the South Geomagnetic conjugate observation of the two stations compared with the IRI model results show that, IRI model application in the polar regions need to be further improved and also give suggestions. The main work of this paper can be concluded as follows: 1. The study on diurnal variations of F layer ionosphere in both Antarctic and Arctic As for foF2, there are magnetism noon phenomena in the autumn of Zhongshan and Spring of Svalbard. And at equinox, the changing range is much bigger than in the other seasons. Summer’s diurnal variation is relatively gentle with small changing range. There is double-hump structure in winter. In Zhongshan, the highest peak appears at magnetism noon, the second highest peak appears around 1700MLT; while in Svalbard, there are no peak value around the magnetism noon but at 08MLT and 18MLT and these two peaks are quite close in value. On the whole, the foF2 in Zhongshan is bigger than in Svalbard. It has nothing to do with solar F10.7 radiation flux. It indicates that the major peak in Zhongshan is relevant to solar-ionized high-density plasma in low-altitude zones passing through polar gap; while the F layer in Svalbard is relative to the auroral particle precipitation.As for hmF2, at equinox, the diurnal variation has an asymmetric“W”shape, whose changing range is much wider. The changing range in summer is relatively small and smooth. And compared with other seasons, the hmF2 in Zhongshan and Svalbard are much similar in shape, yet the average height of Zhongshan is higher than that of Svalbard.2. The study on comparison between observations and IRI in both Antarctic and Arctic.In summer, the foF2 observations in Zhongshan and Svalbard fit the IRI model much better. It is possibly explained by the reason that the IRI model is largely based on the observations at lower altitude which best consider the solar radiation. Similarly, in polar zone the sun is most active in summer and plays a vital part in affecting the ionosphere environment. In winter, the comparison result is the worst. IRI model can not reflect the change of peak value after the noon. It because the sun is always under the horizon for most of time in winter which results in the lack of solar radiation. The auroral particle precipitation is mostly affecting the F layer at equinox and in winter, but not well included in the IRI model. Besides, the hmF2 forecasted is larger than the observations.3. Advice for improving the IRI model to apply to the polar regionThe particular module is needed to describe the ionosphere in polar region under the influence of particle precipitation and plasma convection. As an empirical model based on observation data, more observation stations in polar region are in great need so as to better the IRI model by providing more convincing record.更多还原