Solar atmosphere wave dynamics generated by solar global oscillating eigenmodes

The solar atmosphere exhibits a diverse range of wave phenomena, where one of the earliest discovered was the five-minute global acoustic oscillation, also referred to as the p-mode. The analysis of wave propagation in the solar atmosphere may be used as a diagnostic tool to estimate accurately the physical characteristics of the Sun’s atmospheric layers.In this paper, we investigate the dynamics and upward propagation of waves which are generated by the solar global eigenmodes. We report on a series of hydrodynamic simulations of a realistically stratified model of the solar atmosphere representing its lower region from the photosphere to low corona. With the objective of modelling atmospheric perturbations, propagating from the photosphere into the chromosphere, transition region and low corona, generated by the photospheric global oscillations the simulations use photospheric drivers mimicking the solar p-modes. The drivers are spatially structured harmonics across the computational box parallel to the solar surface. The drivers perturb the atmosphere at 0.5?Mm above the bottom boundary of the model and are placed coincident with the location of the temperature minimum. A combination of the VALIIIC and McWhirter solar atmospheres are used as the background equilibrium model.We report how synthetic photospheric oscillations may manifest in a magnetic field free model of the quiet Sun. To carry out the simulations, we employed the magnetohydrodynamics code, SMAUG (Sheffield MHD Accelerated Using GPUs).Our results show that the amount of energy propagating into the solar atmosphere is consistent with a model of solar global oscillations described by Taroyan and Erdélyi (2008) using the Klein-Gordon equation. The computed results indicate a power law which is compared to observations reported by Ireland et al. (2015) using data from the Solar Dynamics Observatory/Atmospheric Imaging Assembly.     

Ozone chemical equilibrium in the extended mesopause under the nighttime conditions

For retrieval of atomic oxygen and atomic hydrogen via ozone observations in the extended mesopause region (～70–100?km) under nighttime conditions, an assumption on photochemical equilibrium of ozone is often used in research. In this work, an assumption on chemical equilibrium of ozone near mesopause region during nighttime is proofed. We examine 3D chemistry-transport model (CTM) annual calculations and determine the ratio between the correct (modeled) distributions of the O₃ density and its equilibrium values depending on the altitude, latitude, and season.The results show that the retrieval of atomic oxygen and atomic hydrogen distributions using an assumption on ozone chemical equilibrium may lead to large errors below ～81–87?km. We give simple and clear semi-empirical criterion for practical utilization of the lower boundary of the area with ozone’s chemical equilibrium near mesopause.     

计算风工程中 k-ε模型的边界条件研究

从 k-ε湍流模型控制方程入手，对两类满足平衡大气边界层理论要求的入口边界条件进行了详细分析，比较了二者的理论差异。然后以我国公路桥梁抗风规范中建议的 A 类风场为来流条件，定义了相应的 k-ε模型常数与壁面条件，使用两类边界条件进行数值模拟。计算结果表明：两类边界条件结合相应的模型常数与壁面条件，均能在数值模拟中构建基本满足规范要求的平衡大气边界层，但各有其适用范围。在此基础上，对模型常数 C 1和湍动能耗散率与数值模拟结果之间的关系进行了研究，采用修改模型常数与边界条件的方法，改善了数值模拟结果。     

基于能量守恒的再入轻诱饵鉴别方法

针对稀薄大气中的诱饵干扰,提出了一种基于能量守恒定律的再入轻诱饵鉴别方法.该方法利用目标单位质量机械能的损耗表征质阻比的相对大小,实现对轻诱饵的鉴别,避开了质阻比估计的收敛过程.首先根据不同目标的能量方程,推导出目标单位质量机械能损耗的解析表达式,确定了鉴别量;然后理论推导了鉴别量的方差估计式并设计了鉴别门限;最后通过仿真验证了鉴别方法的有效性.     

Numerical simulations of the regional characteristics of dust transport on Mars

Using a Martian general circulation model (GCM), regions favorable for expansion of dust storms on Mars are identified. Dust transport simulations for the northern fall provide global maps of dust expansibility. These global maps show that dust injected from certain areas in the northern mid-latitudes tends to spread widely within a few days. The high expansibility of dust in such areas results from thermal tides, baroclinic waves, and quasi-stationary disturbances. Dust injected into the vast regions around Tharsis and the Sirenum–Aonia regions also tends to spread extensively. However, dust expansion around these two regions largely depends on the local time of dust injection. On the other hand, dust injected at high latitudes in either hemisphere does not spread extensively. Such global maps indicating regions favorable for dust storm expansion are a clue to understanding the expansion processes and climatology of great dust storms on Mars.     

追踪及凝视状态下地气光对空间目标成像影响

为了分析不同探测方式下地气光辐射对空间目标成像特性的影响,利用卫星仿真工具包(satellite tool kit,STK)设计了一个以地球同步轨道(geosynchronous orbit,GEO)卫星与中轨道(medium orbit,MEO)卫星上搭载的可见光成像器为探测平台,以高椭圆轨道(highly elli...     

The Response of the Middle Atmosphere to Solar Cycle Forcing in the Hamburg Model of the Neutral and Ionized Atmosphere

This paper studies the response of the middle atmosphere to the 11-year solar cycle. The study is based on numerical simulations with the Hamburg Model of the Neutral and Ionized Atmosphere (HAMMONIA), a chemistry climate model that resolves the atmosphere from the Earth’s surface up to about 250 km. Results presented here are obtained in two multi-year time-slice runs for solar maximum and minimum conditions, respectively. The magnitude of the simulated annual and zonal mean stratospheric response in temperature and ozone corresponds well to observations. The dynamical model response is studied for northern hemisphere winter. Here, the zonal mean wind change differs substantially from observations. The statistical significance of the model’s dynamical response is, however, poor for most regions of the atmosphere. Finally, we discuss several issues that render the evaluation of model results with available analyses of observational data of the stratosphere and mesosphere difficult. This includes the possibility that the atmospheric response to solar variability may depend strongly on longitude.     

Satellite Measurements of Middle Atmospheric Impacts by Solar Proton Events in Solar Cycle 23

Solar cycle 23 was extremely active with seven of the largest twelve solar proton events (SPEs) in the past forty years recorded. These events caused significant polar middle atmospheric changes that were observed by a number of satellites. The highly energetic protons produced ionizations, excitations, dissociations, and dissociative ionizations of the background constituents in the polar cap regions (>60 degrees geomagnetic latitude), which led to the production of HO_x (H, OH, HO₂) and NO_y (N, NO, NO₂, NO₃, N₂O₅, HNO₃, HO₂NO₂, BrONO₂, ClONO₂). The HO_x increases led to short-lived ozone decreases in the polar mesosphere and upper stratosphere due to the short lifetimes of the HO_x constituents. Polar middle mesospheric ozone decreases greater than 50 % were observed and computed to last for hours to days due to the enhanced HO_x. The NO_y increases led to long-lived polar stratospheric ozone changes because of the long lifetime of the NO_y family in this region. Upper stratospheric ozone decreases of >10 % were computed to last for several months past the solar events in the winter polar regions because of the enhanced NO_y.     

培养学生英语阅读能力

本文主要从理论和实践两个方面，论述立足于四、六级考试，如何科学指导学生进行阅读，提高阅读理解能力。     

发射星都应做热真空试验

介绍了国内外卫星热真空试验的发展概况、卫星热真空试验的重要性及其与常压热循环试验的关系,指出每一颗发射星都应做热真空试验。