北极黄河站极光亚暴期间低热层大气中性风研究

极光亚暴是地球空间基本的能量输入、耦合及耗散过程,其对低热层大气中性风的影响不容忽视,对这一问题进行深入研究具有重要意义.2010年11月,中国北极黄河站(78.92°N,11.93°E)安装了一台自主研制的全天空法布里-珀罗干涉仪(FPI)并开始进行正常观测,为中国首次获得了极光亚暴期间的FPI观测数据.根据2012年越冬期间的观测情况,对2012年11月12-14日及12月09-11日两个极光亚暴事件期间的数据进行处理,计算得到了5级干涉环对应的风场.亚暴期间风场变化与地磁活动变化的对比分析表明,风速的剧烈变化可能是由地磁活动剧烈扰动造成的.针对2012年11月13日00:00UT-02:00UT和2012年12月10日05:00UT-07:30UT的亚暴事件,将全天空相机拍摄到的极光图像与FPI干涉图像对应的视线风场进行对比分析.结果表明在极光活动中,视线风速加强的方向与极光弧的方向垂直,而在极光弧的平行方向,风速相对较小.      

一种用于测量高层大气风场的新型地基Fabry-Perot干涉仪

地表海拔大约250\,km高度处大气非常稀薄,目前被动光学观测是该层风场探测最有效手段.Fabry-Perot干涉仪(FPI)由于具有较高能量利用率及光谱分辨率等特点,是该层大气最有效的地基风场探测仪器之一.基于采用光路缩束系统及滤光片后置(标准具之后)方法研制的小型化FPI,2014年分别在河北廊坊(39.40°N,116.65°E)和山西岢岚(38.71°N,111.58°E)进行了地基观测试验,将观测数据与反演算法相结合得到高层大气风场数据,并将数据结果与美国大气研究中心两台FPI的风场数据进行了比较研究,在气辉整体辐射较弱的情况下得到岢岚站的风速平均反演偏差为11.8 m·s-1.      

氧气A(0,0)波段气辉体发射率和临边辐射强度模拟与分析

临近空间大气参数如温度、密度、风场等对预报模型精度及航天器运行安全等有较大的影响，而气辉的辐射模拟是大气参数反演的重要过程.本文基于光化学模型计算了氧气A（0，0）波段气辉的体发射率和临边辐射强度.基于氧气A（0，0）波段气辉的光化学反应机制、大气动力学和光化学反应理论，建立产生O₂（b1Σ_g+）的光化学模型.计算气辉体发射率，基于临边探测几何路径进行气辉辐射强度模拟.体发射率计算结果与AURIC模型结果的辐射值及辐射高度均一致.基于计算和模拟结果，对氧气A波段气辉体发射率和辐射强度的影响因素进行了分析.      

利用曙暮气辉光度观测研究钠层

通过对钠原子曙暮气辉的18次观测确定了北京北郊上空不同季节钠原子气柱总含量和钠层重心高度等结构参数。结果表明:春夏季钠层重心位置高,秋冬季位置低.冬季观测的平均钠层重心高度为85.67公里;钠原子气柱总含量冬季明显高于其它季节,1月和12月的含量约为6月的7.5倍;冬季钠层也相对地厚.钠层重心高度及总含量的季节变化不仅受D层顶中性和离子化学的制约,而且受到垂直风及子午向或纬向环流的很大影响.     

夜侧极区电离层对流对行星际激波的响应

利用超级双子极光雷达网（Super Dual Aurora Radar Network,SuperDARN）高频雷达、北半球IMAGE地磁台链以及南极中山站的极光观测数据,研究电离层对流对2012年7月14日一个行星际激波扰动事件的响应.在18:10UT行星际激波到达地球并与磁层相互作用触发地磁急始和磁层亚暴,SuperDARN雷达观测到北半球夜侧极区电离层对流显著增强,观测视野覆盖黄河站的Hankasalmi雷达观测到从激波到达地球至18:33UT,电离层F层出现剧烈扰动,雷达回波数明显增多,并出现局部对流速度反转现象.18:33UT之后,观测到F层出现三块速度高达600m·s-1的逆阳运动不规则体.而与Hankasalmi雷达地磁共轭的南半球Kerguelen雷达探测到的回波主要来自E层,回波数量几乎无变化,但是Kerguelen雷达观测视野内的中山站全天空光学成像仪观测到极光活动显著增强.南北半球夜侧电离层观测结果的差异,主要是由于它们分别处于极夜和极昼.      

中国廊坊中间层和低热层大气平均风观测模拟

利用中国廊坊站（39.4°N,116.7°E）流星雷达在2012年4月1日至2013年3月31日的水平风场观测数据,分析廊坊上空80~100km的中间层与低热层（Mesosphere and Lower Thermosphere,MLT）大气平均纬向风和经向风的季节变化特征.结果表明平均纬向风和经向风都表现出明显的季节变化特征.平均纬向风在冬季MLT盛行西风,极大值位于中间层顶,随高度增加西风减弱;在夏季中间层为东风,低热层为强西风,风向转换高度约为82km.平均经向风在冬季以南风为主,在夏季盛行北风.纬向风和经向风在春秋两季主要表现为过渡阶段.流星雷达观测结果与WACCM4模式和HWM93模式模拟的气候变化特点基本一致,但WACCM4模式纬向风和经向风风速偏大,而HWM93模式纬向风和经向风风速偏小.      

利用HRDI/UARS资料分析东亚区域中层大气纬向风气候特征

利用美国高层大气研究卫星(UARS)搭载的高分辨率多普勒测风仪(HRDI)获得的中层大气风场观测资料,对东亚区域中层大气纬向风的垂直分布与变化特征进行了分析研究.多年平均结果显示东亚区域中层大气纬向风具有显著的区域特征,与当前普遍使用的参考大气CIRA-86相比存在显著的不同.在冬季,东亚区域中间层西风急流中心位于25°-35°N之间的75 km高度,与CIRA-86相比,该中心纬度偏南5°,高度偏高10 km;在秋季,东亚区域低热层高度存在一个显著的从赤道到高纬度的东风带,而CIRA-86不存在.分析结果还表明,除了夏季中纬度地区,在东亚区域上空中高层大气各高度上均存在相当显著的区域尺度扰动结构.在热带,低热层高度纬向风无论冬夏,沿纬圈方向都表现出相当显著的不均匀性,夏季这种不均匀性进一步向下扩展到55 km高度.与上述热带扰动特征相比,中纬度地区夏季的纬向风在各个高度沿纬圈相当均匀,但是在冬季,中间层和低热层高度都存在沿纬圈方向显著的纬向风扰动结构.      

重力波对中间层和低热层大气环流的影响

利用β通道准地转近似大气平均运动方程组,采用重力波线性饱和参量化方法,定性地研究大气重力 波对中间层和低热层大气环流的作用.模拟计算得到,大气重力波对平均东西风速可产生100m·s-1／d左右的作 用力和产生120 m2/s的湍流扩散,这些作用平衡了Coriolis扭力,导致大气的平均东西风速大大偏离辐射平衡 风场,中层顶附近的平均东西风速在冬季(夏季)甚至反转为东风(西风).平均东西风速计算结果与冬季和夏季 中频雷达东西风速观测值和大气模式剖面等大致一致.     

135.6nm夜气辉峰值电子密度反演算法及误差

根据夜间135.6nm大气辉光光强与F₂层峰值电子密度N_mF₂平方成正比的物理机制,在前期夜间135.6nm气辉辐射激发模型研究的基础上建立了峰值电子密度的反演算法,把全球经纬度分成若干格点,每个格点的电离层及中性成分信息分别由IRI2000和MSISE90提供,将电离层及中性成分廓线输入夜气辉辐射激发模型,计算每个格点135.6nm气辉的辐射强度,然后将各个格点的135.6nm气辉辐射强度与电离层廓线输入的N_mF₂平方拟合得到气辉强度与N_mF₂的转换因子.利用此方法可获得不同地方时、季节和太阳活动周期的转换因子组成查算表,进而根据实际探测的135.6nm气辉辐射强度反演相应时空的N_mF₂.最后对该算法的反演误差进行了综合分析,为该算法适用的时空特性提供重要理论支撑.      

武汉突发E层的季节变化及其与中层风的关系

通过对2018年武汉站（114.61°E,30.53°N）数字测高仪记录的数据统计分析,研究武汉地区突发E层的特征。研究发现:2018年武汉地区电离层突发E层的临界频率在夏季最高,在冬季有一个次增强现象,在春秋季较低;在正午前最大,在日落后出现小幅度提升,在日出前最低。利用指定动态全球大气气候扩展模型SD-WACCM-X模拟出2018年武汉上空90～140 km高度的平均风场,探讨突发E层与背景风之间的关系,揭示突发E层的形成机制。结果表明,半日潮汐分量可能诱导突发E层临界频率的半日变化,周日潮汐分量诱导突发E层临界频率的周日变化;突发E层的强度可能与纬向风场120 km高度处的风剪切有关。      

中性气体释放人工产生气辉

电离层中分子性的离子与电子的复合要比氧离子与电子的辐射性复合快得多,因此火箭发动机产生的尾气和空间等离子体主动实验中主动释放的中性气体会对电离层有很大的影响,这么大的电离层扰动现象在过去的实验中经常可以观测到.根据中性气体在热层背景中的扩散方程,考虑电离层F区主要的离子化学反应,研究了H2,H2O和CO2气体在电离层高度上的扩散过程和电离层对所释放气体的响应,计算了气辉的体发射系数和发射强度.结果表明,中性气体在电离层高度上扩散非常迅速,在F区的一些高度上,主要正离子成分由O+转变为其他分子离子,且在释放过程中伴随气辉发射,发射气辉的波长和特征与释放物质的种类有关.      

The energy release of substorm and magnetic storm: Its present state and future improvements by KuaFu mission

Considering the KuaFu mission, state of the energy release of substorm and storm is simply presented and it’s improvements by KuaFu mission are investigated. The KuaFu mission will provide us an opportunity to improve our understanding of the energy release during the storm and the substorms. The two KuaFu-B satellites flying in 180° phase-lagged formation in a polar orbit will allow synoptic observations of the auroral oval, central plasma sheet, ring current and other regions. It can monitor the polar region 24/7 continuously. The advantage of the KuaFu mission is to provide the data during all phases of storm and substorm time that can be used to study the global energy release during all phases continuously. The data from auroral imager and other in-situ instruments on board KuaFu-B can be used to study the auroral dynamics and Joule heating during a storm and substorm. The data from the neutral atom imager instrument can be used to study the dynamics and the energy release in the ring current region from sudden commencement to complete storm recovery. Furthermore the data from KuaFu-A, which is around L1 point, can be used to study the interplanetary conditions along with the data from the plasma sheet to study the triggering process and energy release during a substorm. So, KuaFu mission with its continuous time monitoring facilities would enable us to make much progress towards solving the underlying problems.     

Case study of September 24–26, 1998 magnetic storm

We compute global magnetospheric parameters based upon solar wind data obtained from the WIND spacecraft upstream. Using the paraboloid magnetospheric model, calculations of the dynamic global magnetospheric current systems have been made. The solar wind dynamic pressure, the interplanetary magnetic field, the strength of the tail current, and the ring current control the polar cap and auroral oval size and location during the magnetic storm. The model calculations demonstrate that the polar cap and the auroral oval areas are mainly controlled by the tail current. The substorm onset at 0630 UT on September 25, 1998 happened near the minimum in the main phase field depression. The substorm expansion onset time is also marked by a sudden enhancement in the solar wind dynamic pressure and an enhancement in the tail current. The magnetic signatures of these two effects cancel each other, which explains why the D_st profile shows no strong time variation during the substorm. Evidence for the substorm expansion includes not only the signature in the AL index but also the strong asymmetry of the low latitude magnetic disturbances (substorm positive bay signature). Model calculations were checked by comparison with the GOES 8 and 10 magnetic field measurements.     

一种全天空气辉成像仪数据预处理方法和初步结果

大气重力波是大气中的基本波动形式之一,在中高层大气动力和热力学过程中起着十分重要的作用.全天空气辉成像仪是一种以大气气辉辐射为示踪物,能够有效对大气重力波成像的仪器.本文针对中国科学院国家空间科学中心空间天气学国家重点实验室中高层大气组自主研制的全天空气辉成像仪所观测的数据,提出了一种气辉图像预处理方法,进行平场校正、方位校正、星光去除和坐标映射等数据订正.利用该方法处理2015年5月17日21:00BLT至次日05:00BLT西宁台站（36.6°N,101.7°E）的OH气辉数据,发现一次重力波事件,分析并获得了该重力波的水平波长、观测水平相速度和传播方向（分别为17.72km,47m·s-1,339°）.研究结果表明该方法是可行的.      

Sawtooth substorms generated under conditions of the steadily high solar wind energy input into the magnetosphere: Relationship between PC, AL and ASYM indices

Periodicity in occurrence of magnetic disturbances in polar cap and auroral zone under conditions of steady and powerful solar wind influence on the magnetosphere is analyzed on the example of 9 storm events with distinctly expressed sawtooth substorms (N = 48). Relationships between the polar cap magnetic activity (PC-index), magnetic disturbances in the auroral zone (AL-index) and value of the ring current asymmetry (ASYM index) were examined within the intervals of the PC growth phase and the PC decline phase inherent to each substorm. It is shown that the substorm sudden onsets are always preceded by the PC growth and that the substorm development does not affect the PC growth rate. On achieving the disturbance maximum, the PC and AL indices are simultaneously fall down to the level preceding the substorm, so that the higher the substorm intensity, the larger is the AL and PC drop in the decline phase. The ASYM index increases and decreases in conformity with the PC and AL behavior, the correlation between ASYM and PC being better than between ASYM and AL. Level of the solar wind energy input into the magnetosphere determines periodicity and intensity of disturbances: the higher the coupling function E_KL, the higher is substorm intensity and shorter is substorm length. Taking into account the permanently high level of auroral activity and inconsistency of aurora behavior and magnetic onsets during sawtooth substorms, the conclusion is made that auroral ionosphere conductivity is typically high and ensures an extremely high intensity of field-aligned currents in R1 FAC system. The periodicity of sawtooth substorms is determined by recurrent depletions and restorations of R1 currents, which are responsible for coordinated variations of magnetic activity in the polar cap and auroral zone.     

Do we understand the inner magnetotail dynamics during substorms?

Substorm evolution of the near-Earth (|X|<15 R_E) plasma sheet has been emphasized recently because the inner tail is thought to link closely to the substorm auroral activity in the ionosphere during the early stage of substorms. In this paper, we discuss how the inner tail substorm phenomena during the late substorm growth phase and early expansion phase are accounted for by the two prevailing substorm models, namely, the near-Earth neutral line model and the current disruption model. We find that the late growth phase features are more satisfactorily accounted for by the current disruption model than by the near-Earth neutral line model. In addition, detailed observations on current disruption show evidence inconsistent with the proposed idea of dipolarization being due to plasma flow braking from reconnection in the mid-tail region, which poses a difficulty to the near-Earth neutral line model as well.     

关于磁尾高能粒子脉冲的一些特性

利用行星际监察卫星IMP-J取得的高能粒子探测数据(质子能档P4:230keV>E>160keV)与极光电激流指数AE作相关分析,在地心太阳磁层坐标下,按照Fairfield关于中性片对地心太阳磁层"赤道面"的偏离模式,把磁尾分成三个区域:中性片区域、低纬区域和高纬区域。结果表明:(1)高能粒子脉冲的平均强度在中性片区域最强,低纬次之,高纬最弱,表明高能粒子脉冲源区在中性片区域;(2)中性片附近,粒子脉冲和AE指数相关最好,达0.59,低纬次之,高纬几乎无相关,表明粒子脉冲与亚暴事件有关,它是磁尾中性片附近磁力线重联产生的感应电场加速的结果;(3)粒子加速区局限于中性片附近的薄层内,与国外结果完全一致。      

An Introduction to Magnetosphere-Ionosphere-Thermosphere Coupling Small Satellite Constellation

A future Chinese mission is introduced to study the coupling between magnetosphere, ionosphere and thermosphere, i.e. the Magnetosphere-Ionosphere-Thermosphere Coupling Small Satellite Constellation (MIT). The scientific objective of the mission is to focus on the outflow ions from the ionosphere to the magnetosphere. The constellation is planning to be composed of four small satellites; each small satellite has its own orbit and crosses the polar region at nearly the same time but at different altitude. The payloads onboard include particle detectors, electromagnetic payloads, auroral imagers and neutral atom imagers. With these payloads, the mission will be able to investigate acceleration mechanism of the upflow ions at different altitudes. Currently the orbits have been determined and prototypes of some have also been completed. Competition for next phase selection is scheduled in late 2015.      

Modeling of ionospheric parameter variations in East Asia during the moderate geomagnetic disturbances

The results of modeling of ionospheric disturbances observed in the East Asian region during moderate storms are presented. The numerical model for ionosphere–plasmasphere coupling developed at the ISTP SB RAS is used to interpret the data of observations at ionospheric stations located in the longitudinal sector of 90–130°E at latitudes from auroral zone to equator. There is obtained a reasonable agreement between measurements and modeling results for winter and equinox. In the summer ionosphere, at the background of high ionization by the solar EUV radiation in the quiet geomagnetic period the meridional thermospheric wind strongly impacts the electron concentration in the middle and auroral ionosphere. The consistent calculations of the thermospheric wind permit to obtain the model results which are closer to summer observations. The actual information about the space-time variations of thermosphere and magnetosphere parameters should be taken into account during storms.