Solar Energetic Particle Composition, Energy Spectra, and Space Weather

Recent progress in measuring the composition and energy spectra of solar energetic particles (SEPs) accelerated by CME-driven shocks is reviewed, including a comparison of the observed charge-to-mass dependence of breaks in SEP spectra with model predictions. Also discussed is a comparison of SEP and CME kinetic energies in seventeen large SEP events, and estimates of the SEP radiation dose that astronauts would be subject to once they venture outside the protective cover of Earth’s magnetosphere.     

Cosmic Rays at High Heliolatitudes

The Ulysses spacecraft has been the first to orbit the Sun over its poles and to explore the heliosphere at these high heliolatitudes. It has now completed two fast latitude scans, one at solar minimum and one at solar maximum. Since its launch in October 1990, this mission has led to several surprising discoveries concerning energetic particles, cosmic rays, Jovian electrons, the solar wind, the heliospheric magnetic field and the global features of the heliosphere. This review addresses mainly the propagation and modulation of cosmic rays and other charged particles, from both an observational and theoretical point of view, with emphasis on what has been learned from exploring the inner heliosphere to high heliolatitudes. This is done for solar minimum and maximum conditions. The review is concluded with a summary of the main scientific discoveries and insights gained so far from the Ulysses mission.     

On the Differences in Composition between Solar Energetic Particles and Solar Wind

Although the average composition of solar energetic particles (SEPs) and the bulk solar wind are similar in a number of ways, there are key differences which imply that solar wind is not the principal seed population for SEPs accelerated by coronal mass ejection (CME) driven shocks. This paper reviews these composition differences and considers the composition of other possible seed populations, including coronal material, impulsive flare material, and interplanetary CME material.     

通过e+e-→-ff过程探测BH

最小Higgs模型(LH)预言了重规范玻色子BH的存在。为此计算了它对e e-→f(f=l,b,c)过程的贡献,研究了在未来的高能线性e e-对撞(ILC)实验中发现该粒子的可能性,该实验的质心能量S=500GeV,￡int=340fb-1。结果表明在合理的参数空间内,完全可以探测到该新粒子的可能物理信号。     

Extension of the low diffusion particle method for near-continuum two-phase flow simulations

The low diffusion (LD) particle method, proposed by Burt and Boyd, is modified for the near-continuum two-phase flow simulations. The LD method has the advantages of easily coupling with the direct simulation Monte Carlo (DSMC) method for multi-scale flow simulations and dramatically reducing the numerical diffusion error and statistical scatter of the equilibrium particle methods. Liquidor solid-phase particles are introduced in the LD method. Their velocity and temperature updating are respectively, calculated from the motion equation and the temperature equation according to the local gas properties. Coupling effects from condensed phase to gas phase are modeled as momentum and energy sources, which are respectively, equal to the negative values of the total momentum and energy increase in liquid or solid phase. The modified method is compared with theoretical results for unsteady flows, and good agreements are obtained to indicate the reliability of the one-way gas-to-particle coupling models. Hybrid LD-DSMC algorithm is implemented and performed for nozzle discharging gas-liquid flow to show the prospect of the LD-DSMC scheme for multi-scale two-phase flow simulations.     

基于PSO-GA优化的TOP-HAT形态学滤波器及其应用

针对机栽红外图像中运动弱小点目标检测的难题,提出了一种基于PSO-GA训练参数的形态学滤波器.以粒子群优化算法(Particle Swarm Optimization,PSO)为主线,按PSO算法中标准的速度和位置更新,遗传算法(Genetic Algorithm,GA)采用新的区间离散化编码和自适应的主次式交叉与变异算子,将遗传算法与粒子群优化算法的自动更新特征结合在一起,通过优化搜索全局空间获得形态学滤波器的最优参数,进而确保优化的形态学滤波器具有良好的滤波性及时效性.通过对低信噪比红外图像(SNR约为2)的测试,检测概率可以达到98％以上,与利用神经网络(Neural Network,NN)训练结构元素后的Top-Hat形态学滤波器相比提高了2％ ～3％.与GA算法相对,训练算法效能提高20％,提高了搜索最佳值的能力.     

壁湍流等动量区对惯性颗粒分布的影响

对摩擦雷诺数为1000、颗粒Stokes数为1.0的含颗粒槽道湍流进行了直接数值模拟,采用高斯函数叠加法提取了等动量区的模态速度,对各等动量区内的颗粒分布进行了分析。发现在高动量的核心区,颗粒平均浓度高于非核心区,而浓度脉动低于非核心区。在等动量区界面上,流体速度和颗粒浓度变化剧烈,展向涡结构的出现导致了局部颗粒浓度较低。在等动量区的界面以下,在较高的壁面法向位置,存在大尺度的浓度幅值低而浓度脉动高的结构,其等值线分布与核心区/非核心区界面一致。     

Characteristics of solar particle events at Mars relative to Earth

While not specifically designed to detect solar energetic particle radiation, the Electron Reflectometer onboard Mars Global Surveyor (MGS/ER) collected such data from January 1999 through October 2006. Energetic protons (?25 MeV) and other ions penetrated the MGS/ER shielding and registered counts within the instrument’s electronics. During solar particle events (SPE’s), prolonged enhancements in the particle background were observed at Mars with time intensity profiles similar to Earth based SPE observations. Throughout the lifespan of MGS/ER, 85 distinct SPE’s were observed. Basic characteristics of Mars based SPE observations and the frequency of SPE occurrences at Mars are compared to corresponding Earth based observations. Approximately 22% of SPE’s that occurred during MGS/ER operation were observed at Earth but not Mars. Similarly, 19% of SPE’s were observed at Mars but not Earth. Time intensity profiles at Earth and Mars match predictions provided in the literature, based on the physical location of the detector with respect to the motion of the interplanetary shock wave. Note: The work described herein was largely conducted as part of a doctoral dissertation produced by the author.     

Comparison of organ dose and dose equivalent for human phantoms of CAM vs. MAX

For the evaluation of organ dose and dose equivalent of astronauts on space shuttle and the International Space Station (ISS) missions, the CAMERA models of CAM (Computerized Anatomical Male) and CAF (Computerized Anatomical Female) of human tissue shielding have been implemented and used in radiation transport model calculations at NASA. One of new human geometry models to meet the “reference person” of International Commission on Radiological Protection (ICRP) is based on detailed Voxel (volumetric and pixel) phantom models denoted for male and female as MAX (Male Adult voXel) and FAX (Female Adult voXel), respectively. We compared the CAM model predictions of organ doses to those of MAX model, since the MAX model represents the male adult body with much higher fidelity than the CAM model currently used at NASA. Directional body-shielding mass was evaluated for over 1500 target points of MAX for specified organs considered to be sensitive to the induction of stochastic effects. Radiation exposures to solar particle event (SPE), trapped protons, and galactic cosmic ray (GCR) were assessed at the specific sites in the MAX phantom by coupling space radiation transport models with the relevant body-shielding mass. The development of multiple-point body-shielding distributions at each organ made it possible to estimate the mean and variance of organ doses at the specific organ. For the estimate of doses to the blood forming organs (BFOs), data on active marrow distributions in adult were used to weight the bone marrow sites over the human body. The discrete number of target points of MAX organs resulted in a reduced organ dose and dose equivalent compared to the results of CAM organs especially for SPE, and should be further investigated. Differences of effective doses between the two approaches were found to be small (<5%) for GCR.     

基于分布式模型预测控制的多UAV协同区域搜索

针对多无人机(UAV)协同区域搜索问题展开研究。提出了一种基于分布式模型预测控制(DMPC)的多UAV分布式优化搜索方法。首先基于传统的搜索图模型,建立了多UAV协同搜索的问题描述和状态空间模型,然后在DMPC框架下,将集中式多UAV在线优化决策问题转化为各架UAV的小规模分布式优化问题,采用基于纳什最优和粒子群优化(PSO)相结合的算法实现对每个子系统优化问题的迭代求解。仿真结果表明:DMPC方法能够有效地降低多UAV协同搜索决策问题的求解规模,是一种可行的方法。