Solar Isotopic Composition as Determined Using Solar Energetic Particles

Solar energetic particles (SEPs) provide a sample of the Sun from which solar composition may be determined. Using high-resolution measurements from the Solar Isotope Spectrometer (SIS) onboard NASA’s Advanced Composition Explorer (ACE) spacecraft, we have studied the isotopic composition of SEPs at energies ≥20 MeV/nucleon in large SEP events. We present SEP isotope measurements of C, O, Ne, Mg, Si, S, Ar, Ca, Fe, and Ni made in 49 large events from late 1997 to the present. The isotopic composition is highly variable from one SEP event to another due to variations in seed particle composition or due to mass fractionation that occurs during the acceleration and/or transport of these particles. We show that various isotopic and elemental enhancements are correlated with each other, discuss the empirical corrections used to account for the compositional variability, and obtain estimated solar isotopic abundances. We compare the solar values and their uncertainties inferred from SEPs with solar wind and other solar system abundances and find generally good agreement.     

Relative fluxes of shock and prompt peaks in SEP event time profiles

Peak fluxes are an important property of gradual solar energetic particle (SEP) event time profiles from both astro/heliophysical and applications perspectives. However, the peak flux in an event may occur at the event onset, or at the time of the interplanetary shock arrival (the ESP or energetic storm particles). This makes an important difference in the interpretation of the peak flux, and in any attempts to characterize or model it. This paper describes a study of SEP data sets from ACE, IMP-8 and GOES toward determining the relative properties of these peak fluxes for protons with energies near 1, 10, and 50 MeV. The results suggest that for gradual events with both peaks, the ESP peak often dominates at 1 MeV energies and is dominant about half the time at 10 MeV. Moreover, the prompt peak fluxes can be used to estimate the shock peak (ESP event) up to days ahead, especially in the lower energy range.     

Effect of “Noisy” sun conditions on aircrew radiation exposure

In computer codes used to estimate the aircrew radiation exposure from galactic cosmic radiation, a quiet sun model is usually assumed. A revised computer code (PCAIRE ver. 8.0f) is used to calculate the impact of noisy sun conditions on aircrew radiation exposure. The revised code incorporates the effect of solar storm activity, which can perturb the geomagnetic field lines, altering cutoff rigidities and hence the shielding capability of the Earth’s magnetic field. The effect of typical solar storm conditions on aircrew radiation exposure is shown to be minimal justifying the usual assumptions.     

Lunar geophysical parameters inversion based on gravity/topography admittance and particle swarm optimization

This paper presents a FORTRAN computer program. The program as code will be used for lunar parameter inversions based on gravity/topography admittance. This will be done by assuming that the lunar lithosphere is modeled as a thin elastic spherical shell. The parameters discussed here include; load ratio, crustal thickness, subsurface load depth, crustal density and elastic lithosphere thickness. The admittance of the best-fitting model can be found through automatically adjusting misfits between one theoretical admittance and an observed one. The results in this paper indicate that this research’s theoretical model is reasonable for exploring the best-fitting parameters. In addition, this code is not only able to automatically and simultaneously calculate the global optimum solution of the parameters studied, but also performs well in computational speed. The code can be easily modified to include more parameter inversions; such as the inversion for subsurface density anomaly and the case of considering infilling material in some lunar mare basins.     

PIV 技术测量振荡射流流场

利用以大功率双脉冲激光器为光源的ＰＩＶ技术，测定了由扁平射流和尖劈组成的二维振荡射流流场。实验结果表明，射流喷嘴与尖劈之间存在交错的、旋转方向相反的涡街，从而在尖劈两侧形成压力扰动。这种压力扰动波与不稳定射流的相互作用是整个系统产生流体振荡的原因。此外，还分析了射流喷嘴与尖劈之间的距离对流场的影响规律。     

自由飞行下基于IPS算法的碰撞风险研究

自由飞行是解决空域拥挤问题的一种有效飞行模式。随着通信、导航、监视（ CNS ）技术的不断进步和自由飞行理论的不断完善,自由飞行将会使飞机由被动指挥向自选最优路径转变,能够明显提高空域的容量和飞行的效率。在评估自由飞行环境下飞机运行的安全性时,需要行之有效的碰撞风险评估方法。首先考虑通信、导航、监视（CNS）性能对飞机定位误差的影响,在执行飞行冲突解脱命令过程中引入相互作用粒子系统（IPS）,提出一种自由飞行下飞机碰撞风险评估算法,最后结合目标安全水平寻找最优最小安全间距。算例表明,算法能够快速有效计算自由飞行下飞机间碰撞风险,具有可行性。     

The effect of the longitudinal propagating waves on the electron acceleration in the reconnecting current sheet

Based upon the most efficient electron acceleration near the midplane of 3D non-neutral driven reconnecting current sheet (RCS) and the electrostatic wave excitation by the drift Maxwellian distribution of electrons in Vlasov simulation, we assume that the electrostatic waves mainly propagate opposite to the reconnecting electric field and investigated how these waves affect the electron acceleration. The main results are: (1) when the electron’s velocity equals to the phase speed of the waves, they will be trapped and have the different accelerating characteristics from the untrapped electrons through solving the momentum equations of electrons analytically; (2) the test particle simulations further prove that the number of the energetic electrons decreases with the increasing intensity of unstable waves, and the distribution of the energetic electrons takes on the double power-law.     

Aerodynamic multi-objective integrated optimization based on principal component analysis

Based on improved multi-objective particle swarm optimization (MOPSO) algorithm with principal component analysis (PCA) methodology,an efficient high-dimension multiobjective optimization method is proposed,which,as the purpose of this paper,aims to improve the convergence of Pareto front in multi-objective optimization design.The mathematical efficiency,the physical reasonableness and the reliability in dealing with redundant objectives of PCA are verified by typical DTLZ5 test function and multi-objective correlation analysis of supercritical airfoil,and the proposed method is integrated into aircraft multi-disciplinary design (AMDEsign) platform,which contains aerodynamics,stealth and structure weight analysis and optimization module.Then the proposed method is used for the multi-point integrated aerodynamic optimization of a wide-body passenger aircraft,in which the redundant objectives identified by PCA are transformed to optimization constraints,and several design methods are compared.The design results illustrate that the strategy used in this paper is sufficient and multi-point design requirements of the passenger aircraft are reached.The visualization level of non-dominant Pareto set is improved by effectively reducing the dimension without losing the primary feature of the problem.     

First millimetric detections of AE Aquarii

We report the first millimetric detections of the magnetic cataclysmic variable AE Aquarii, accompanied by contemporaneous microwave observations. These data show that the time-averaged spectrum is well fit by a power-law which extends to mm wavelengths. We suggest that the spectrum is consistent with that expected from a superposition of flare-like events.