Gravity wave mixing effects on the OH*-layer

Based on an advanced numerical model for excited hydroxyl (OH*) we simulate the effects of gravity waves (GWs) on the OH*-layer in the upper mesosphere. The OH* model takes into account (1) production by the reaction of atomic hydrogen (H) with ozone (O₃), (2) deactivation by atomic oxygen (O), molecular oxygen (O₂), and molecular nitrogen (N₂), (3) spontaneous emission, and (4) loss due to chemical reaction with O. This OH* model is part of a chemistry-transport model (CTM) which is driven by the high-resolution dynamics from the KMCM (Kühlungsborn Mechanistic general Circulation Model) which simulates mid-frequency GWs and their effects on the mean flow in the MLT explicitly. We find that the maximum number density and the height of the OH*-layer peak are strongly determined by the distribution of atomic oxygen and by the temperature. As a results, there are two ways how GWs influence the OH*-layer: (1) through the instantaneous modulation by O and T on short time scales (a few hours), and (2) through vertical mixing of O (days to weeks). The instantaneous variations of the OH*-layer peak altitude due to GWs amount to 5–10 km. Such variations would introduce significant biases in the GW parameters derived from airglow when assuming a constant pressure level of the emission height. Performing a sensitivity experiment we find that on average, the vertical mixing by GWs moves the OH*-layer down by ~2 to 7 km and increases its number density by more than 50%. This effect is strongest at middle and high latitudes during winter where secondary GWs generated in the stratopause region account for large GW amplitudes.     

航空发动机进气道出口截面喘振波的分布

用扰流插板使涡扇发动机进气道内产生不对称分布的总压畸变并使发动机出现喘振。在进气道出口即发动机进口截面测取两种不同转速下发动机的喘振压力波。应用小波分析奇异点理论,采用模极大值原理和高阶Daubechies小波多尺度分析,对喘振压力信号进行处理,得到发动机喘振波在其进口截面的波形分布特征。揭示了在两种转速下,喘振波在截面上的分布相似,其频率和幅值与转速成正比。截面中心部分表现为正脉冲,周围部分为负脉冲。在垂直方向上的幅值较大,而两翼较小。对该分布特征进行了分析,初步的推论为:高压压气机引起喘振,稳态压力畸变最严重的区域和未受到畸变扰动的区域,喘振波最为强烈。     

对流层雷暴源所产生的柱形重力波

已有充分的证据表明, 大气对流层的雷暴迹象是大气中间层重力波活动的显著代表源.在雷暴迹象的上方, 通过火箭已观测到大气中间层出现的热效应, 也已通过雷 达探测到大气平流层出现的上行重力波, 从地面和卫星平台上观察到夜间气辉有序而 成环状的重力波波形. 所有这些实验结果都与位于观测点下方的雷暴活动有紧密联系. 此类雷暴通常主要集中在中国东部沿海以及地球其他沿海海湾地域. 关于此类雷暴对大 气中间层的影响尚未被充分研究和了解. 为能有效地探究其成因, 利用所开发的一个二维计算机数值模型模拟和研究大气对流层的雷暴源所引发的上行重力波, 进而揭示 此类重力波产生的基本物理机理, 及其在大气中间层的能量耗散. 通过模拟研究发现, 雷暴源可以大面积高强度地聚集和释放积雨云的能量, 当这种周期性的对流变化引发大气对流层的不稳定性后, 就会有圆柱体重力波的产生和传播.      

Heating heavy ions in the polar corona by collisionless shocks: A one-dimensional simulation

Recently a new model for explaining the observations of preferential heating of heavy ions in the polar solar corona was proposed ( and ). In that model the ion energization mechanism is the ion reflection off supercritical quasi-perpendicular collisionless shocks in the corona and the subsequent acceleration by the motional electric field E = −V × B/c. The mechanism of heavy ion reflection is based on ion gyration in the magnetic overshoot of the shock. The acceleration due to the motional electric field is perpendicular to the magnetic field, giving rise to large temperature anisotropy with T_⊥ ? T_∥, in agreement with SoHO observations. Such a model is tested here by means of a one dimensional test particle simulation where ions are launched toward electric and magnetic profiles representing the shock transition. We study the dynamics of O⁵⁺, as representative of coronal heavy ions for Alfvénic Mach numbers of 2–4, as appropriate to solar corona. It is found that O⁵⁺ ions are easily reflected and gain more than mass proportional energy with respect to protons.     

正丁醇/煤油混合物非预混燃烧压力振荡特性

为探索生物混合燃料在燃气轮机燃烧室内的应用,将丁醇掺混入航空煤油中,根据燃烧室的实验结果构建熵波对流模型,定量分析其不同体积分数对燃烧室内压力振荡频率的影响。实验结果表明:在燃烧室进口压力1.98 MPa、温度600 K和油气比0.03下,随着丁醇所占体积分数增大,燃烧室内压力振荡频率逐渐下降,而幅值变化无明显规律。熵波对流模型结果与实验吻合较好,通过分析表明,不同燃料组分热值变化引起的对流时间改变,是燃烧室压力振荡频率变化的主要原因,为控制燃烧室内压力振荡提供了参考。      

Determination of the Kelvin-Helmholtz Wave Parameters on the Magnetopause in Single-spacecraft Observations

Kelvin-Helmholtz (K-H) waves are formed from the triggeringof the K-H instability on the magnetopause, which is a candidatemechanism for solar wind entry into the magnetosphere, especially undernorthward interplanetary magnetic field conditions. In this study, aK-H wave event was identified from the observation of probe Bof the Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission on 15 May 2008. A new method to determinethe wave parameters of the K-H waves in single-spacecraft observationsis proposed. The dominant wave period is determined by three kinds ofspectrograms for three key parameters, namely the ion density, the iontemperature, and the z component of magnetic field. The phasevelocity is estimated by calculating the center-of-mass velocity of thedetected K-H vortex region. This approximation is validated bycomparison with other alternative methods. The method to determine thewave parameters is a first step to further study K-H wave properties and their relationship with interplanetaryconditions.      

An analytical model of prominence dynamics

Solar prominences are magnetic structures incarcerating cool and dense gas in an otherwise hot solar corona. Prominences can be categorized as quiescent and active. Their origin and the presence of cool gas ($～{10}^4$?K) within the hot ($～{10}^6\text{K}$) solar corona remains poorly understood. The structure and dynamics of solar prominences was investigated in a large number of observational and theoretical (both analytical and numerical) studies. In this paper, an analytic model of quiescent solar prominence is developed and used to demonstrate that the prominence velocity increases exponentially, which means that some gas falls downward towards the solar surface, and that Alfvén waves are naturally present in the solar prominences. These theoretical predictions are consistent with the current observational data of solar quiescent prominences.     

Effects of dust polarity and nonextensive electrons on the dust-ion acoustic solitons and double layers in earth atmosphere

Propagation of dustion acoustic solitary waves (DIASWs) and double layers is discussed in earth atmosphere, using the Sagdeev potential method. The best model for distribution function of electrons in earth atmosphere is found by fitting available data on different distribution functions. The nonextensive function with parameter $q=0.58$ provides the best fit on observations. Thus we analyze the propagation of localized waves in an unmagnetized plasma containing nonextensive electrons, inertial ions, and negatively/positively charged stationary dust. It is found that both compressive and rarefactive solitons as well as double layers exist depending on the sign (and the value) of dust polarity. Characters of propagated waves are described using the presented model.     

“嫦娥4号”月球背面着陆区月壳及深部结构特征

深部月壳和月幔物质结构是月球科学探测的关键问题之一。“嫦娥4号”初步将月球背面南极—艾肯（South Pole-Aitken,SPA）盆地内的冯·卡门（Von Kármán）撞击坑作为着陆点,具有重要的科学研究价值。结合月球重力、地形、布格重力、月壳厚度等地球物理数据,综合对冯·卡门撞击坑的月壳及其深部结构特征进行了分析。结果显示：冯·卡门撞击坑重复撞击到南部的冯·卡门M撞击坑上,后者的中央峰具有明显的布格正重力异常和线性的布格重力梯度特征,显示出高密度的幔部物质向上涌起;冯·卡门撞击坑极有可能穿透了该区域的整个月壳,并挖掘出了深部月幔的物质;该区域南部月壳厚度较薄小于5 km,北部平均月壳厚度在15～20 km,月壳平均密度为2 630 kg·m^-3,比背面高地月壳密度高,且平均孔隙度为9%,低于月球的平均孔隙度12%。     

On the origin of cosmic rays in the spiral galaxy NGC 3310

The problem of cosmic ray production in the spiral galaxy NGC 3310 is addressed by analysing and comparing optical and radio continuum data. Tentative results indicate that on global scales relativistic electrons may be produced in the shock front associated with teh density wave while on local scales extreme population I objects may be producing them. It is inferred that the same conclusions apply to all cosmic rays produced in the disk.