用经验模式参数研究电离层发电机效应

本文利用MSIS-86和IRI-86模式的基本参数,求得热层风系和电导率的三维分布;继而从发电机理论得到了电离层电位及层电流密度在北半球的分布和变化。本研究将大量数据统计平均的大气模式参数与热层、电离层理论研究联系了起来。     

国际参考电离层模型输出参数峰值高度性能

电离层峰值高度HmF2是描述电离层形态的重要参数之一,国际参考电离层模型IRI-2016中融入了大量电离层测高仪和无线电掩星探测数据,用以提升HmF2的预测精度.本文利用太阳活动低年(2007-2010年)气象、电离层和气候卫星联合观测系统COSMIC探测数据描述全球范围内COSMIC HmF2的三维形态变化,对比分析...     

MSIS-86和IRI-86模式的扩展应用

本文简要地介绍了MSIS-86和IRI-86两个模式,并用此两模式所给的参数推算出热层中性大气风系、碰撞频率和电离层电导率的时空分布。      

太阳活动下降年昆明地区TEC变化特征与IRI-2020模拟比较分析

利用昆明低纬度测站（24.7°N,102.9°E，磁纬15.1°N）2016-2019年的观测数据和最新版的国际参考电离层（IRI-2020）模拟结果，对昆明地区电离层总电子含量（TEC）在太阳活动下降年期间的变化特征及与模型输出进行对比研究。结果表明,昆明TEC存在明显的春秋高值、夏冬低值的半年异常；白天高值、夜间低值的日变化特点突出，日峰值出现在06:30-08:00 UT（约13:00-15:00 LT）;TEC随太阳活动减弱而明显下降，年平均峰值在2016-2019年分别为48,33,27,24 TECU；日峰值TEC与F10.7存在显著相关，月均值相关系数达到0.86，而与Ap指数则表现为弱相关；IRI-2020能较好地模拟昆明地区TEC的季节变化，但与观测值存在较大差异；均方根偏差值多集中在2～15 TECU，相对偏差百分比值主要在–85%～50%范围变化。对比结果表明IRI-2020的预测精度仍有待提高。     

IRI-2007预测TEC在广州地区的适用性分析

利用广州站(23.2°N, 113.3°E) GPS双频接收机监测的电离层TEC数据和IRI-2007模型不同电离层输入参数计算得到的TEC预测值, 对比分析了太阳活动低年(2008年)广州地区TEC的变化特征. 结果表明, TEC观测值周日变化在16:00LT左右达到最大值, 而IRI-TEC最大值出现时间较GPS-TEC提前1h左右. TEC季节变化在春秋分较高, 两至季节较低, 表现出明显的半年特性和季节依赖性, 并出现冬季异常现象. IRI-TEC与GPS-TEC在白天具有较好的一致性, 夜间偏差较大. 不同电离层输入参数得到的TEC预测值也相差较大, 选用顶部电子密度参数NeQuick、底部厚度参数B0 Table并用URSI系数计算F₂层峰值参数时, 能较好地反映TEC观测值的变化特征. 在对磁暴的响应上, 预测值无明显变化, 观测值则有比较明显的表现. 通过对比, 初步分析了利用IRI-2007模型预测TEC在广州地区的适用性, 并给出了合理的参数选择方案.      

IRI-2007对扩展F的预测与观测比较研究

通过对赤道地区两台站的扩展F 实际观测值与IRI-2007 模型预测值的比较, 研究了该模型预测结果的地域局限性和预测的准确度. 该模型建立在美洲扇区赤道附近台站资料基础上, 本文选取非洲扇区大体同纬度两个台站资料进行对比研究. 统计结果表明, 无论在发生概率日均值的年变化趋势上, 还是在扩展F 发生率年均值随地方时变化以及随太阳活动的统计中, 都存在着明显的差异; 而对非洲两站实测值的分析和IRI-2007 模型对南美巴西地区的预测又分别与当前已有的研究结果相符. 分析结果表明, (1) 建立在巴西台站数据基础上的IRI-2007 模型的统计建模极具参考价值; (2) 赤道和低纬度电离层扩展F 现象有强烈的经度效应, 在该模型建模方法基础上, 结合不同扇区实际资料的统计, 能改进该模型全球应用的普适性; (3) IRI-2007模型能正确反映巴西地区扩展F 的发生概率, 用该模型和其他扇区不同条件下的实测值对比, 提供了一个细致研究扩展F经度效应的基础, 有利于确认导致扩展F发生的基本条件和多种影响因素的具体作用.      

基于IRI背景场的单站电离层TEC地图重构技术

为了有效解决电离层TEC观测数据稀疏时重构问题, 引入IRI-2007作为背景场, 利用反距离加权法和克里格方法重构了电离层TEC地图, 使用交叉检验方法检验了引入背景场前后的重构精度. 结果表明, 引入背景场后, 一方面有效地控制了边缘地区的发散现象, 另一方面重构网格点上绝对误差在 -0.25~0.25 TECU之间的比例分别提高了约70 %和100 %, 误差统计基本呈正态分布. 可以通过引入更加精确的背景场或使用逐步订正方法进一步提高重构精度.      

我国电离层基本参量与国际参考模式的比较

本文利用我国满洲里、北京、武昌、重庆和广州等台站电离层观测记录,对各层临界频率的实测值(月中值)与IRI-86的计算值进行了分析比较.|发现两者存在着显著而系统的偏离.E层和F₁层偏离较小F₂层偏离较大,其相对值有时超过60%.总的来说,f₀F₂的相对偏离:夜间大,白天小冬季大,夏季小太阳活动低年大,高年小随着纬度降低偏离增大模式值普遍大于实测值.      

南京地区斜向加热电离层效应数值模拟

与垂直加热相比,斜向加热电离层具有灵活性高、影响范围广和便于实际操作等优势.在非偏区考虑欧姆吸收,基于电子能量方程和连续性方程构建电波斜向加热低电离层的物理模型,并利用IRI-2007和NRLMSISE-00经验模型提供的背景参数对南京地区斜向加热低电离层进行数值模拟,对比不同加热条件下电子温度和电子密度的扰动情况.研究结果表明:电波加热效果随入射仰角和有效辐射功率的增大而增大;电子温度和电子密度增幅随电波频率增大而减小;X波模比O波模造成的电子温度扰动幅度和电子密度扰动幅度更大,同时X波模比O波模能更快地使电子温度和电子密度达到稳定状态;一定范围内较小仰角、较低频率、较大有效辐射功率的电波能使电子密度更快达到稳定,后两者还能加快电子温度达到稳定的过程;电子温度达到稳定所需时间随入射电波仰角呈单峰变化,仰角为62°时达到最大.      

正相电离层骚扰研究

本文对我国五个电离层站月报资料中的正相电离层骚扰(f₀F₂增加)作了分析研究,获得了正相骚扰时空变化的规律性,地磁暴与正相电离层骚扰的关系.对正相电离层骚扰的机理也作了讨论.      

Evaluation of the improvement of IRI-2016 over IRI-2012 at the India low-latitude region during the ascending phase of cycle 24

This paper investigated the performance of the latest International Reference Ionosphere model (IRI-2016) over that of IRI-2012 in predicting total electron content (TEC) at three different stations in the Indian region. The data used were Global Positioning System (GPS) data collected during the ascending phase of solar cycle 24 over three low-latitude stations in India namely; Bangalore (13.02°N Geographic latitude, 77.57°E Geographic longitude), Hyderabad (17.25°N Geographic latitude, 78.30°E Geographic longitude) and Surat (21.16°N Geographic latitude, 72.78°E Geographic longitude). Monthly, the seasonal and annual variability of GPS-TEC have been compared with those derived from International Reference Ionosphere IRI-2016 and IRI-2012 with two different options of topside electron density: NeQuick and IRI01-corr. It is observed that both versions of IRI (i.e., IRI-2012 and IRI-2016) predict the GPS-TEC with some deviations, the latest version of IRI (IRI-2016) predicted the TEC similar to those predicted by IRI-2012 for all the seasons at all stations except for morning hours (0500 LT to 1000?LT). This shows that the effect of the updated version is seen only during morning hours and also that there is no change in TEC values by IRI-2016 from those predicted by IRI-2012 for the rest of the time of the day in the Indian low latitude region. The semiannual variations in the daytime maximum values of TEC are clearly observed from both GPS and model-derived TEC values with two peaks around March-April and September-October months of each year. Further, the Correlation of TEC derived by IRI-2016 and IRI-2012 with EUV and F10.7 shows similar results. This shows that the solar input to the IRI-2016 is similar to IRI 2012. There is no significant difference observed in TEC, bottom-side thickness (B0) and shape (B1) parameter predictions by both the versions of the IRI model. However, a clear improvement is visible in hmF2 and NmF2 predictions by IRI-2016 to that by IRI-2012. The SHU-2015 option of the IRI-2016 gives a better prediction of NmF2 for all the months at low latitude station Ahmedabad compare to AMTB 2013.     

Evaluation of the IRI-2007 model options for the topside electron density

The International Reference Ionosphere (IRI) 2007 provides two new options for the topside electron density profile: (a) a correction of the IRI-2001 model, and (b) the NeQuick topside formula. We use the large volume of Alouette 1, 2 and ISIS 1, 2 topside sounder data to evaluate these two new options with special emphasis on the uppermost topside where IRI-2001 showed the largest discrepancies. We will also study the accurate representation of profiles in the equatorial anomaly region where the profile function has to accommodate two latitudinal maxima (crests) at lower altitudes but only a single maximum (at the equator) higher up. In addition to IRI-2001 and the two new IRI-2007 options we also include the Intercosmos-based topside model of Triskova, Truhlik, and Smilauer [Triskova, L., Truhlik, V., Smilauer, J. An empirical topside electron density model for calculation of absolute ion densities in IRI. Adv. Space Res. 37 (5), 928–934, 2006] (TTS model) in our analysis. We find that overall IRI-2007-NeQ gives the best results but IRI-2007-corrected provides a more realistic representation of the altitudinal–latitudinal structure in the equatorial anomaly region. The applicability of the TTS model is limited by the fact that it is not normalized to the F2 peak density and height.     

Global validation of IRI TEC for high and medium solar activity conditions

The IRI model offers a choice of options for the computation of the electron density profile and electron content (TEC). Recently new options for the topside electron density profile have been developed, which have a strong impact on TEC. Therefore it is important to test massively the IRI and the new options with experimental data. A large number of permanent stations record dual frequency GPS data from which it is possible to obtain TEC values. Thirty-one worldwide distributed stations have been selected to investigate the capabilities of the IRI to reproduce experimental TEC. Data for years 2000 (high solar activity) and 2004 (medium solar activity) have been analyzed computing modeled values with the IRI-2001 and the IRI-2007-NeQuick topside options. It is found that IRI-2007-NeQuick option generally improves the estimate of the slant TEC, especially in the case of high latitudes stations during high solar activity.     

中纬度观测的电离层F区经度效应及其模式计算

利用1956—1994年期间分别在长春和乌鲁木齐两观测站上观测的f0F2和f0F1月中值,定量分析了两站上观测的经度效应,讨论了产生两站上经度效应的可能物理机制,并与国际参考电离层模式的结果进行了比较．     

国际参考电离层IRI－90与中国实测电离层月平均电子密度剖面形状的比较

将太阳活动峰年期间中国4个电离层站垂直探测得到的月平均电子浓度剖面与国际参考电离层IKI-90进行了系统的比较。结果表明国际参考电离层所计算的峰下电子含量(或峰下半厚)总体来说偏大。一天中白天符合较好,晚上较差,对中纬台站较好,对低纬台站较差。