第23太阳活动周武汉站电离层TEC特征分析

利用武汉站(30.5°N, 114.4°E)1997年1月1日至2007年12月31日电离层TEC、太阳黑子数及地磁指数等资料, 分析了第23周武汉站TEC的周日变化、季节变化、半年变化以及与太阳活动的相关性等特征; 以2006年4月13-17日发生的磁暴为例, 讨论了武汉站TEC对磁暴的响应以及可能的机理. 结果表明,武汉站电离层TEC在太阳活动高、低年均呈典型的周日变化特征; 冬季异常和半年异常特征明显, 且受太阳活动强弱影响; TEC和太阳黑子数年均值相关系数为0.9611; TEC对磁暴的响应可能是由磁层穿透电场和中性风共同作用导致的, 具体影响机制有待深入研究.      

用STARE-TRIAD联合观测对磁层-电离层不完全耦合的实例研究

本文用STARE-TRIAD联合观测的一个实例研究磁层-电离层不完全耦合现象.实例中观测的电场、场向电流和推出的Pederson电导率在Harang不连续区的分布与用Kan-Lee磁层-电离层不完全耦合理论的预测值符合得很好.这支持了该理论所说的在电等位U-位形低纬侧有S-位形存在以及与之相应的电离层电导率的第二增强区和电场凹陷区等现象.STARE的其他观测事实说明这些现象具有一定的普遍意义.      

用数值模拟的方法研究磁暴主相期间影响环电流分布特征的要素

环电流是距离地心2～7 Re的带电粒子围绕地球西向漂移形成的.环电流的增强将引起全球磁场的降低,反映了地磁暴的强度.磁暴主相期间,对流电场驱动等离子体片中的能量粒子经历E×B漂移与俘获注入环电流,进入损失锥的粒子沉降到大气中.本文采用磁暴主相期间环电流离子分布的模型,结合上述因素研究不同离子能量下对流电场对环电流离子通量的直接影响,以及强弱对流电场下环电流能量离子投掷角的变化,并从物理上阐述造成此种通量分布特性的原因.      

太阳风-磁层-电离层耦合过程中的能量收支

太阳风向磁层电离层(Magnetosphere and Ionosphere, MI)系统输入能量, 而输入的能量随后在MI系统中消耗. 本文从能量守恒原理出发, 讨论太阳风-磁层-电离层 (SMI)耦合过程中的能流路径和能量收支的定量关系. 主要讨论9个问题: (1) 太阳风向MI系统的能量输入, (2) MI系统对能量输入的响应, (3) 环电流的能量消耗, (4) 极区电离层焦耳加热的能量消耗, (5) 极光粒子沉降的能量消耗, (6) 磁尾能量的消耗、储存以及返回下游太阳风, (7)平静期间的能量积累与释放, (8)能量在不同能汇中的分配, (9)评价能量函数的准则和方法.      

中低纬电离层不同季节地磁暴响应的事例分析

利用中国中低纬台站漠河（53.5°N,122.3°E）、北京（40.3°N,116.2°E）、武汉（30.5°N,114.2°E）和三亚（18.3°N,109.6°E）的电离层观测数据,对比分析了4个台站电离层参数在2015年不同季节4个地磁扰动事件期间的变化特征.结果表明,4个磁暴事件期间电离层的响应特征并不完全一致,有着明显的季节特征,春季、夏季和秋季电离层以负相扰动为主,冬季以正相扰动为主.分析发现,中性成分O/N₂的降低与电离层负相扰动有关,但三亚地区的负相扰动还与扰动发电机电场相关.正相扰动的机制在不同事件中并不相同,穿透电场可能是引起春季磁暴事件期间电离层短时正暴效应的原因,而冬季长时间的正暴效应则是扰动电场和中性风共同作用的结果.      

磁层-电离层电动耦合与中纬地磁指数的变化

本文探讨磁层一电离层耦合过程内中纬地磁指数的变化特点,并与极光电集流和赤道电集流(指数)变化相比较。相关分析和时序叠加分析均表明,高、中、低纬地磁指数变化可归结为磁层一电离层电动耦合的统一物理图象。有R事件的磁暴主相初期和无R事件的磁扰期内,赤道电集流和中纬地磁指数的变化各不相同。这再次证明,耦合分析中将磁层源扰动的直接穿透作用与经电离层内动力过程的效应二者加以区分和综合研究是很重要的。      

中性原子成像探测的物理设计与仿真

研究了磁层-电离层-热层耦合星座(MIT)卫星计划中高能中性原子成像仪(NAIS-H)探测方案的原理设计和模拟仿真. 以双星中性原子成像仪设计思想为基础,依据MIT卫星计划的总体科学目标和磁层卫星的轨道环境及相应自旋姿态,给出中性原子成像仪的技术架构,并针对地磁偶极场的环电流模型进行了模拟仿真. 仿真结果表明,所研制的NAIS-H以其高时空分辨能力适用于监测和反演磁暴期间磁层等离子体的全球动力学过程.      

磁暴期间中低纬电离层暴形态和物理机制分析

本文利用东亚地区１２个低纬电离层台站的测高仪观测数据，对１９７８年８月２７日发生的一次曲型磁暴期间电离层峰值高度和密度的变化进行了分析。采用滑动平均区分开电离层中不同时间尺度的扰动，分析了影响中低纬度电离层暴的几种扰动形态特征，并对其物理机制进行了讨论。结果表明：伴随磁暴急始的磁层压缩，电离层中表现出峰值密度增加和峰值高度下降；磁暴主相期间热层大气暴环流及其所引起的中性大气成分变化控制着电离层的大     

地磁暴期间中国中低纬电离层的CIT研究

利用电离层层析成像技术(Computerized Ionospheric Tomography, CIT)处理115°E子午圈附近6个台站的GPS观测数据, 分析了2004年11月地磁暴期间中国中低纬电离层的响应情况. 结果表明, 电离层呈正相扰动, 且不同高度上的响应不同, 800 km以下电子密度有不同程度的增加, 且在峰值高度附近增幅最大, 800 km以上地磁暴的影响并不显著; 伴随地磁能量的注入, 赤道异常峰极向扩展; 随磁扰强度的降低, 电子密度也逐渐恢复至平静水平. 这些结果与以往的理论和观测结果一致, 初步估计扰动是由热层暴环流引起的, 并受到赤道异常峰移动的影响.      

Volland对流电场模型的实验参数

本文将几个地面和卫星观测结果结合起来给出Volland对流电场模型的实验参数.结果能很好地与GEOS-2卫星所测得的等离子体层顶运动特征、STARE雷达测得的Harang不连续性的运动及近年来探测的磁层电离层电场相吻合.文章指出只要Volland电场模型的参数由实验确定后, 将更有助于磁层和电离层物理的研究.      

低纬电离层等离子体块相关等离子体泡演化期间的虚高变化

针对东亚地区地磁低纬度南北半球Vanimo台站(地理2.7°S,141.3°E;地磁11.2°S,146.2°W)和海南台站(地理19.5°N,109.1°E;地磁9.1°N,179.1°W)上空的3个电离层等离子体块与等离子体泡相关联的事件,利用地面台站的电离层测高仪连续观测数据,研究等离子体泡演化期间的电离层虚高变...     

Statistical average estimates of high latitude field-aligned currents from the STARE and SABRE coherent VHF radar systems

Two bistatic VHF radar systems, STARE and SABRE, have been employed to estimate ionospheric electric fields in the geomagnetic latitude range 61.1 – 69.3° (geographic latitude range 63.8 – 72.6°) over northern Scandinavia. 173 days of good backscatter from all four radars have been analysed during the period 1982 to 1986, from which the average ionospheric divergence electric field versus latitude and time is calculated. The average magnetic field-aligned currents are computed using an AE-dependent empirical model of the ionospheric conductance. Statistical Birkeland current estimates are presented for high and low values of the Kp and AE indices as well as positive and negative orientations of the IMF B_z component. The results compare very favourably to other ground-based and satellite measurements.     

基于因果卷积与LSTM网络的电离层总电子含量预报

电离层总电子含量（TEC）不仅是分析电离层形态的关键参数之一,同时为导航及定位等空间应用系统消除电离层附加时延提供重要支撑。由于电离层TEC的时空变化特征,本文融合因果卷积和长短时记忆网络,以太阳活动指数F_10.7、地磁活动指数Dst和电离层TEC历史数据作为特征输入,构建深度学习模型,实现提前24 h预报电离层TEC。进一步利用2005－2013年连续9年的CODE TEC数据,全面评估了模型在北京站（40°N,115°E）、武汉站（30.53°N,114.36°E）和海口站（20.02°N,110.38°E）的预报性能。结果显示不同太阳活动条件下三个站的TEC值与真实测量值的相关系数都大于0.87,均方根误差大都集中在0～1 TECU以内,且模型预报精度与纬度、太阳、地磁活动程度、季节变化相关。与仅由长短时记忆网络构成的预报模型相比,本实验模型均方根误差降低了15%,为电离层TEC预报模型的实际应用提供了参考。      

Controlling factors of Region 2 field-aligned current and its relationship to the ring current: Model results

One essential component of magnetosphere and ionosphere coupling is the closure of the ring current through Region 2 field-aligned current (FAC). Using the Comprehensive Ring Current Model (CRCM), which includes magnetosphere and ionosphere coupling by solving the kinetic equation of ring current particles and the closure of the electric currents between the two regions, we have investigated the effects of high latitude potential, ionospheric conductivity, plasma sheet density and different magnetic field models on the development of Region 2 field-aligned currents, and the relationship between R2 FACs and the ring current. It is shown that an increase in high latitude potential, ionospheric conductivity or plasma sheet density generally results in an increase in Region 2 FACs’ intensity, but R2 FACs display different local time and latitudinal distributions for changes in each parameter due to the different mechanisms involved. Our simulation results show that the magnetic field configuration of the inner magnetosphere is also an important factor in the development of Region 2 field-aligned current. More numerical experiments and observational results are needed in further our understanding of the complex relationship of the two current systems.     

华南地区电离层闪烁的时空分布特征研究

利用位于赤道异常区的广州(23.17°N, 113.34°E)和茂名(21.45°N, 111.31°E)两台站2011年7月至2012年6月观测到的GPS电离层闪烁数据, 分析比较了这两地电离层闪烁出现的逐月变化及地方时变化和空间分布特征. 结果表明, 中等强度闪烁(S₄ > 0.4)和强闪烁(S₄ > 0.6)的出现均呈现明显季节分布规律, 两站的闪烁活动均表现出春秋强, 冬夏弱的特点, 在时间上主要发生在20:00LT-24:00LT; 从空间分布来看, 两站的闪烁活动在2011年秋季, 闪烁出现的区域比较分散, 而在2012年春季, 主要在两站上空区域出现的闪烁最为频繁.      

电离层电场对磁层活动响应时延的模式研究

本文用极盖边界上电离层驱动电位φ₀随时间变化的不同模式计算了场向电流J_∥2及电离层对流电场E的演化过程。计算表明,当φ₀(t)先升后降有极大值时,J_∥2(t)和E(t)也表现出类似的趋势。但它们的极值滞后于φ_0max出现的时刻,即在一段时间内,φ₀虽已开始下降,J_∥2及高纬E却继续增大。一般说,E先于J_∥2达到极值,但相差甚小。φ₀变化形式不同时,滞后时间亦不同。当φ₀陡升缓降时,E、J_∥2的极值相对于φ_0max的时延可超过一小时。这与持续时间较长的磁暴期间所观测到的电离层场强响应时延量级是一致的。时延大小还受电离层电导率的制约。低纬电离层场强的响应与高纬不同,其升降趋势与φ₀同步。      

利用TIE-GCM模式计算电离层电流及夜间电离层磁场

电离层电流产生的磁场是地磁场卫星测绘时需要剔除的干扰源.利用电离层热层模式TIE-GCM计算电离层中的中性风、重力驱动和压强梯度等形成的电离层电流的全球分布,分析电流在特定位置产生的磁场及磁场三分量随纬度的变化规律.结果表明,E层尤其是磁赤道和极区的电流密度较大,可达103nA·m-2量级,F层电流密度量级约为10nA·m-2.在磁静日（Kp≤ 1）夜间22:00LT-04:00LT,电离层电流在中低纬度（南北纬50°之间）产生的磁场量级为几个nT,且磁场的南北向分量和径向分量基本大于东西向分量.通过与CHAMP卫星磁测数据分析比较,发现TIE-GCM模式计算电离层干扰磁场在中低纬度可以取得较好的结果,但在高纬度地区的效果不理想,还需进一步改进模式以提高计算精度.      

Importance of electric field measurement over low latitudes at stratospheric heights by balloons

The vertical field in the stratosphere around 35 km is predominantly of atmospheric origin whereas the horizontal electric field at these altitude is mainly of ionospheric origin. The electrical coupling between ionosphere and atmosphere is not known for low latitudes. Balloon borne electric field measurements are planned from Hyderabad, India (geographic latitude 17.5° N) to understand this coupling. Measurement of stratospheric electric fields are also important from the point of view of the sun-weather relationship. It si suggested that the balloon borne electric field measurements are important to understand the electrodynamics of the middle atmosphere.     

Observation of the north-south asymmetry in the equatorial spread F intensity at the Brazilian longitude

This study presents an analysis of the observed north-south asymmetry of the range spread F (RSF) intensity at the low latitude region during an equinoctial month of different solar epochs (2002, 2015 and 2017). The ionospheric parameters were obtained during geomagnetic quiet days from four digisonde stations located along the Brazilian longitude, which include a dip equator station (Sao Luiz (SL: 2.33 S, 44.2 W)), conjugate stations (Campo Grande (CG: 20.5°S, 55°W) and Boa Vista (BV: 2.8°N, 60.7°W)) and another low latitude station (Cachoeira Paulista (CP: 22.7°S, 45°W)). The results highlight the competing effect of the post-sunset electric field strength and the trans-equatorial wind on the latitudinal distribution of the irregularity intensity at both hemispheres under varying background ionospheric condition. The RSF intensity was seen to reduce as the solar flux index decreased and the latitudinal peak shifted closer to the dip equator. This was dependent on the variation of the field line mapped irregularity spectrum and the density gradient. Likewise, the north-south asymmetry in the irregularity occurrence was seen to become more significant as a denser ionosphere was observed at the hemisphere with the equatorward meridional wind. This has further proven that the non-linear cascading of the plasma irregularity across the low latitude region is strongly influenced by the local electric field.     

Statistical study of the time delay of ionospheric TEC storms to geomagnetic storms in Taoyuan,Taiwan

We have studied the time delay of ionospheric storms to geomagnetic storms at a low latitude station Taoyuan (25.02°N, 121.21°E), Taiwan using the Dst and TEC data during 126 geomagnetic storms from the year 2002 to 2014. In addition to the known local time dependence of the time delay, the statistics show that the time delay has significant seasonal characteristics, which can be explained within the framework of the seasonal characteristics of the ionospheric TEC. The data also show that there is no correlation between the time delay and the intensity of magnetic storms. As for the solar activity dependence of the time delay, the results show that there is no relationship between the time delay of positive storms and the solar activity, whereas the time delay of negative storms has weakly negative dependence on the solar activity, with correlation coefficient −0.41. Especially, there are two kinds of extreme events: pre-storm response events and long-time delay events. All of the pre-storm response events occurred during 15–20 LT, manifesting the Equator Ionospheric Anomaly (EIA) feature at Taoyuan. Moreover, the common features of the pre-storm response events suggest the storm sudden commencement (SSC) and weak geomagnetic disturbance before the main phase onset (MPO) of magnetic storms are two main possible causes of the pre-storm response events. By analyzing the geomagnetic indices during the events with long-time delay, we infer that this kind of events may not be caused by magnetic storms, and they might belong to ionospheric Q-disturbances.