甚低频电磁波变态低电离层的数值模拟

利用由波对电离层加热的模型和适合于夜间低电离层的离子化学模型构成的综合模型，对甚低频波射入低电离层时变态电离层的程度受中性成分参数变化及低电离层离子化学反应参数的影响进行了模拟计算．计算结果表明，中性成分的浓度与温度及电离层离子化学反应参数密切地影响着加热的效果．     

中层大气钠层的流星蒸发模式

本文计算了地球中层大气的钠层模式。在此模式中,流星蒸发是形成钠层的源而尘埃的吸附足汇。本文考虑和比较了有关钠层形成机制的已往工作中所出现过的所有光化学反应,选出了四十个合理而重要的化学反应作为本模式的化学基础。模式也考虑进了高度变化的涡流扩散和带电粒子受地磁场作用的向下飘移等机制。本文对各化学反应和模式中各个因素的重要性作了比较和评价。本文计算结果表明,在各高度上中层大气中的钠及其化合物的相对浓度主要取决于化学反应过程本身,与源、汇及各层间扩散机制等关系不大。虽然在钠层模式计算中必须考虑到十种钠成分,但105公里以上主要成分足钠离子(Na+)。80公里以下主要成分是氢氧化钠(NaOH)。80公里到105公里间主要成分是中性钠原子(Na)。所有成分的总浓度主要地取决于源和汇随高度的分布。大气背景及电离常数的变化可以引起钠层相当显著的季变化和周日变化。理论计算结果与历年来的观测结果作比较后可以看到两者大体上符合得相当好。      

美研制“月球运输联络飞船”用离子发动机

美国喷气推进实验室(JPL)正在研讨向月球基地输送物资的“月球运输联络飞船”上的离子发动机的研究计划。假如使用由离子发动机和太阳电池组合而成的“月球运输联络飞船”,建设月球基地就比使用化学火箭更为经济。 JPL的计划是使用推力为0.2牛的60台氙-离子发动机和300千瓦的太阳电能帆板,用航天飞机将其送入300公里高度的轨道上。所采用的2块帆板宽12米、长61米,帆板、控制装置以及离子发动机占“月球运     

低功率氮氢电弧加热发动机非平衡数值模拟

文章对低功率氮氢电弧加热发动机进行了双温度化学非平衡数值模拟研究,模型中包含总的能量方程和电子能量方程,等离子体组分包括分子、原子、离子和电子等7个组分,采用的化学动力学模型中包含了氮氢组分解离、电离等重要的动力学过程,气体的物性根据当地的组分和温度实时计算。通过计算获得了发动机内部气体温度及各组分数密度分布。结果表明,发动机轴线附近等离子体接近热力学平衡,而在发动机阳极壁面电弧贴附区域等离子体明显偏离热力学平衡;计算获得的组分分布表明电弧加热发动机内存在反混合过程,即发动机内各组分分布与入口浓度分布明显不同。氢组分由发动机中心到阳极壁面沿径向呈现先减小后增大的趋势;而氮组分的浓度分布趋势与氢组分相反;进一步的分析表明,发动机内各组分的扩散主要受到气体解离和电离过程引起的浓度梯度所驱动。     

平流层上部负离子成分的直接测量和硫酸离子热化学分析

本文报道了在法国南部(44°N)上空进行的两次气球飞行实验的部分负离子成分探测结果.利用自然负离子谱计算了某些硫酸离子的热化学常数ΔG, ΔH和ΔS.讨论了上升段测量中气球表面放气造成的离子化学污染.      

高能离子辐照下薄膜界面化学结合增强的模型

近年来高能离子辐照引起的薄膜附着力增强现象及其应用受到了广泛的重视。由于高能离子一固体相互作用的复杂性,目前对附着力增强的物理机制的认识还不清楚。文章基于高能离子辐照引起界面原子化学结合键增强的思想,建立了薄膜附着力增强的理论模型,并由此得到辐照离子阈剂量与离子能量损失(电子阻止能力)及其界面原子结合键能的分析表达式,计算结果与实验结果很好吻合。理论分析表达式说明,膜附着力增强的阈剂量受界面原子结构、元素种类、电子阻止能力及其形成固体径迹所损失的能量等多种因素有关。     

基于CFD的10 cm氙离子推力器阳极推进剂供给方式优化

离子推力器阳极推进剂在放电室内的浓度分布及其变化梯度的设计是放电室放电模式可靠性设计的关键技术之一,直接影响到放电室内推进剂的电离效率及放电稳定性。针对航天器在轨多目标飞行任务对10 cm氙离子推力器的应用需求,为提高10 cm氙离子推力器放电室空腔内阳极推进剂供给的均匀性,实现推进剂利用率的有效提升,运用计算流体动力学（CFD）理论,建立了包括阳极推进剂、进气管和分配环在内的CFD阳极环模型,研究了未发生气体放电情况下,不同供给方式时阳极环内阳极推进剂的压强与流速变化情况。在此基础上,分析了阳极推进剂供给方式对10 cm氙离子推力器放电室空腔内阳极推进剂分布特性的影响作用关系。将优化前后的阳极环在10 cm氙离子推力器中进行了性能对比,结果表明:优化后阳极推进剂电离损耗由277.9 W/A降至241.2 W/A,放电室阳极推进剂利用率由91.7%提升至98.4%,验证了CFD计算结果的正确性与方法的可行性。研究结果为离子推力器放电室拓扑结构设计与优化提供了方法。      

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.     

地球轨道卫星气动力工程近似计算

本文以漫反射理论模型和修正牛顿理论为基础,提出一套计算近地卫星气动力的工程近似方法,推荐二种通用气动函数表。根据本文所介绍的计算公式和函数表格,经过简单算术运算,即可求出各种理论外形(轴对称组合几何体)在轨道运行段和再入大气层过程中气动力系数。大量计算表明:飞行高度在135公里以上时完全可按自由分子流理论计算,飞行高度在80公里以下时完全可按连续流理论计算,中间过渡区可利用自由分子流和连续流的计算值进行半经验修正。     

小型箭载SF_6主动释放装置研究

化学物质释放是空间物理主动试验的重要手段之一.构建了一种基于探空火箭平台的SF_6气体释放装置,其具有体积小、自重轻、对运载平台要求低等优点,当装置自身质量为6kg时可实现2 kg的SF_6气体释放.仿真计算了SF_6气体在电离层高度的扩散过程和相应的电离层离子化学过程.研究结果表明,本装置能够有效消减电离层电子密度,具有较高实用价值.     

The influence of radiative cooling and turbulence on the heat budget of the thermosphere

Numerical models of the thermal budget of the Earth's upper atmosphere in the height range of 90–500km are developed. The main sources and sinks of energy including infra-red radiative cooling by vibrational-rotational bands of NO, CO₂, OH and O₃ as well as heating and cooling arising from dissipation of turbulent energy and eddy heat transport are taken into account. The calculated temperature and density height profiles are in good agreement with the respective profiles from CIRA 72 and Jacchia 1977 models. It is shown for the models considered that IR-radiative cooling by CO₂ and NO in the 15μ and 5.3μ bands, not eddy turbulence provides the major loss of heat from 90 to 180km.     

不同上边界条件下的极区电离层数值模拟

利用一维自洽的极区电离层模型,研究了沿磁力线方向不同电离层-磁层耦合条件下极区电离层的响应.此模型在110-610km的电离层空间区域内,综合求解描述极区电离层的连续性方程、动量方程和能量方程,以得到电离层数值解.研究发现,上边界条件在200 km以上的高度能显著地影响电离层参量的形态.较高的O+上行速度对应较低的F层峰值和较高的电子温度.不同边界O+上行速度对应的温度高度剖面完全不同.200km以上电子温度高度剖面不但由来自磁层的热流通量所控制,同时还受到场向O+速度的影响.对利用电离层模型研究电离层内部物理过程提出了建议.      

Latitudinal influences on the quiet daytime D-region

Four versions of a steady-state quiet D-region model are presented. They differ from each other as a result of latitudinal differences in total neutral particle concentrations, nitric oxide concentrations and cosmic ray ionization rates. The total ion concentration profiles of all four versions have minima near 70 km which range from about 10⁸ m^?3 at high latitudes to 3.5 × 10⁷ m^?3 at equatorial latitudes for a solar zenith angle of 60°. Neutral density differences among the four cases result in important vertical shifts for the respective D-region profiles relative to one another. A “C-layer” is evident for the high and mild-latitude models at large solar zenith angles. The altitude where the negative ion/electron concentrations ratio is unity varies from about 63 to 67 km. The computed results are compared briefly with the extensive data base in the literature.     

A three-dimensional modelling study of the processes leading to mid latitude nitric oxide increases in the lower thermosphere following periods of high geomagnetic activity

The processes leading to enhancements in mid latitude nitric oxide (NO) densities following geomagnetic storms have been investigated using the University College London (UCL) Coupled Middle Atmosphere and Thermosphere (CMAT) general circulation model. A comparison of calculated storm time and quiet time NO densities at 110 km altitude reveals the presence of aurorally produced NO at both high and mid latitudes for several days after subsidence of activity. At 150 km, the NO enhancements are shorter lived and remain for up to approximately 2 days after the storm. By separating the contribution of chemical production and loss, horizontal and vertical advection, and molecular and eddy diffusion in the calculation of NO densities, we show that at 150 km altitude, horizontal transport must be taken into consideration if post-storm mid latitude enhancements are to be reproduced. Chemical production of NO at high latitudes continues for up to 2 days after subsidence of a storm at altitudes of around 150 km. We show that equatorward winds at this altitude are sufficiently strong to transport the aurorally produced NO to mid latitudes. Vertical diffusion transports NO from altitudes of 150 km and above, to lower altitudes where it is longer lived. At 110 km altitude, chemical, diffusive and advective terms must all be included in the calculation of NO density in order to simulate realistic mid latitude enhancements. We propose that it is the combined effects of increased chemical production, downward diffusion from altitudes of 150 km and above, and transport by winds that lead to increases in mid latitude NO density at altitudes of around 110 km. This is the first detailed study of the causes of post-storm mid latitude NO enhancements to use a three-dimensional general circulation model.     

一氧化氮对电离层电子密度的影响

本文利用电离层电子密度的理论计算模式,研究了一氧化氮对中、低纬度100-200km间电子密度的影响,发现电子密度与一氧化氮密度间存在着正、负相关。正相关,只有当这一光电离成为一氧化氮离子的主要生成源时才出现。      

Accuracy of IRI profiles of ionospheric density and temperatures derived from comparisons to Kharkov incoherent scatter radar measurements

The incoherent scatter radar (ISR) facility in Kharkov, Ukraine (49.6°N, 36.3°E) measures vertical profiles of electron density, electron and ion temperature, and ion composition of the ionospheric plasma up to 1100 km altitude. Acquired measurements constitute an accurate ionospheric reference dataset for validation of the variety of models and alternative measurement techniques. We describe preliminary results of comparing the Kharkov ISR profiles to the international reference ionosphere (IRI), an empirical model recognized for its reliable representation of the monthly-median climatology of the density and temperature profiles during quiet-time conditions, with certain extensions to the storm times. We limited our comparison to only quiet geomagnetic conditions during the autumnal equinoxes of 2007 and 2008. Overall, we observe good qualitative agreement between model and data both in time and with altitude. Magnitude-wise, the measured and modeled electron density and plasma temperatures profiles appear different. We discovered that representation accuracy improves significantly when IRI is driven by observed-averaged values of the solar activity index rather than their predictions. This result motivated us to study IRI performance throughout protracted solar minimum of the 24th cycle. The paper summarizes our observations and recommendations for optimal use of the IRI.     

Observations of solar-flare ionization in the mesosphere using coherent-scatter radar

Observations of solar-flare ionization in the mesosphere can be made using coherent-scatter radar systems. The scattered power profiles they measure in the 60–90 km altitude region is a function of the ion concentration gradient and the intensity of turbulent mixing at each atltitude. By comparing the power profiles before, during and after a solar flare, it is possible to estimate the ion production rate during the flare as a function of altitude and time. This analysis is used to compare the ion production rates with generally accepted ion-chemical models. Comparisons are made with ion production rates estimated from the solar X-ray flux for the same flare made by geostationary satellites.     

Positive ion composition and electron density in a combined auroral and NLC event

The positive ion composition and electron density were measured in the lower ionosphere above Kiruna in salvo A of CAMP (Cold Arctic Mesopause Project). The CAMP/P (S37/P) payload carrying a magnetic ion spectrometer, positive ion and electron probes, and propagation experiments was launched on 3 August 1982 2332 UT during extended Noctilucent Clouds (NLC) and auroral activities over Kiruna. The measured electron density was 5×10³cm^?3 at 80 km and 2.5×10⁵cm^?3 at 90 km. The increase of ion and electron densities in the D- and E-region during twilight was caused by precipitating auroral particles. The height distribution of the positive ions measured by the mass spectrometer in the mass range 19–280 amu is different from a winter flight with similar auroral conditions. Below 85.5 km proton hydrates H⁺(H₂O)₃ ? H⁺(H₂O)₈ were the dominant ions. The heaviest proton hydrates H⁺(H₂O)₇ and H⁺(H₂O)₈ were most abundant at 82–85.5 km, the altitude of visible NLC. Above 85.5 km O₂⁺ and NO⁺ became dominant. A small metal ion layer was observed between 90.5–93 km with a maximum ion density of 10% of the total positive ion density at 91 km altitude. The metal ion density disappeared within about a km below 90.5 km.     

Assessment of precision in ionospheric electron density profiles retrieved by GPS radio occultations

The Constellation Observing System for Meteorology Ionosphere and Climate (COSMIC) is a six satellite radio occultation mission that was launched in April 2006. The close proximity of these satellites during some months after launch provides a unique opportunity to evaluate the precision of Global Positioning System (GPS) radio occultation (RO) retrievals of ionospheric electron density from nearly collocated and simultaneous observations. RO data from 30 consecutive days during July and August 2006 are divided into ten groups in terms of daytime or nighttime and latitude. In all cases, the best precision values (about 1%) are found at the F peak height and they slightly degrade upwards. For all daytime groups, it is seen that electron density profiles above about 120 km height exhibit a substantial improvement in precision. Nighttime groups are rather diverse: in particular, the precision becomes better than 10% above different levels between 120 and 200 km height. Our overall results show that up to 100–200 km (depending on each group), the uncertainty associated with the precision is in the order of the measured electron density values. Even worse, the retrieved values tend sometimes to be negative. Although we cannot rely directly on electron density values at these altitudes, the shape of the profiles could be indicative of some ionospheric features (e.g. waves and sporadic E layers). Above 200 km, the profiles of precision are qualitatively quite independent from daytime or latitude. From all the nearly collocated pairs studied, only 49 exhibited a difference between line of sight angles of both RO at the F peak height larger than 10°. After analyzing them we find no clear indications of a significant representativeness error in electron density profiles due to the spherical assumption above 120 km height. Differences in precision between setting and rising GPS RO may be attributed to the modification of the processing algorithms applied to rising cases during the initial period of the COSMIC mission.