Polar caps and auroral zones under idealized axisymmetric magnetic fields

The geomagnetic field, modified by the solar wind, determines the shape, area and location of polar caps and auroral zones, among other magnetosphere and upper atmosphere characteristics. Since the field varies greatly with time it is of interest to analyze polar caps and auroral zones variations linked to magnetic field variations of intensity and pattern. Polar caps and auroral zones locations and areas for various single harmonic axial field configurations are obtained analytically assuming a simple magnetopause model. As the axial degree n increases, the polar caps and auroral zones total number, given by n + 1 and 2n respectively, also increase. However, their total areas decrease from a larger value in the case of an axial dipole to a minimum for an axial octupole (n = 3), and then increase for increasing degrees. The increasing rate is much higher in the auroral zones case to the point that it exceeds the dipolar value at n = 5 while in the polar caps case this occurs at n = 8. The absolute latitudes of the auroral zones and polar caps that reside around the geographical poles increase with axial degree. Our results represent an end-member case of the evolution of auroral zones and polar caps during polarity reversals if the transition involves axial dipole energy cascade to higher axial degrees. Evidence for such an energy transfer is found in the historical record of the geomagnetic secular variation.     

Impact of a novel hybrid accelerometer on satellite gravimetry performance

The state-of-the-art electrostatic accelerometers (EA) used for the retrieval of non-gravitational forces acting on a satellite constitute a core component of every dedicated gravity field mission. However, due to their difficult-to-control thermal drift in the low observation frequencies, they are also one of the most limiting factors of the achievable performance of gravity recovery. Recently, a hybrid accelerometer consisting of a regular EA and a novel cold atom interferometer (CAI) that features a time-invariant observation stability and constantly recalibrates the EA has been developed in order to remedy this major drawback. In this paper we aim to assess the value of the hybrid accelerometer for gravity field retrieval in the context of GRACE-type and Bender-type missions by means of numerical closed-loop simulations where possible noise specifications of the novel instrument are considered and different components of the Earth’s gravity field signal are added subsequently. It is shown that the quality of the gravity field solutions is mainly dependent on the CAI’s measurement accuracy. While a low CAI performance (10^?8 to 10^?9?m/s²/Hz^1/2) does not lead to any gains compared to a stand-alone EA, a sufficiently high one (10^?11?m/s²/Hz^1/2) may improve the retrieval performance by over one order of magnitude. We also show that improvements which are limited to low-frequency observations may even propagate into high spherical harmonic degrees. Further, the accelerometer performance seems to play a less prominent role if the overall observation geometry is improved as it is the case for a Bender-type mission. The impact of the accelerometer measurements diminishes further when temporal variations of the gravity field are introduced, pointing out the need for proper de-aliasing techniques. An additional study reveals that the hybrid accelerometer is – contrary to a stand-alone EA – widely unaffected by scale factor instabilities.     

紧缩场超高频（UHF）天线测试方法的研究

针对CCR120／100紧缩场超高频（UHF）天线测试的问题，根据紧缩场的现有条件，给出了利用紧缩场进行UHF天线辐射特性测试的方法，以及进一步提高测试精度的方法，以满足卫星UHF频段天线辐射特性测试的需求。     

A geomagnetic activity forecast for improving the efficiency of aeromagnetic surveys in Greenland

In recent years several aeromagnetic surveys were carried out in Greenland and more will be carried out in the future. We describe some of the characteristics pertinent to surveys in Greenland and the problems faced and experiences made by the survey teams working there, with special emphasis on the west coast where most surveys were conducted. Both unfavorable terrestrial weather and space weather appear to complicate survey planning. We discuss possible options available to the survey teams for mitigating the adverse effect of part of the problems, namely survey data contamination by intense geomagnetic activity. The implementation of a prototype geomagnetic activity forecast service as an aid to planning survey flights is discussed in more detail. The forecast service was tested by an independent observer, and the performance of the scheme is evaluated by a subsequent comparison between forecast and actual measurements. The comparison rendered largely acceptable results, but their validity is limited by the fact that the two-month test interval was characterized by a mostly relatively quiet magnetic field.     

Modeling and analysis of Earth’s gravity field measurement performance by inner-formation flying system

The Earth’s gravity field can be measured with high precision by constructing the purely gravitational orbit of the inner-satellite in Inner-formation Flying System (IFS), which is independently proposed by Chinese scholars and offers a new way to carry out gravity field measurement by satellite without accelerometers. In IFS, for the purpose of quickly evaluating the highest degree of recovered gravity field model and geoid error as well as analyzing the influence of system parameters on gravity field measurement, an analytical formula was established by spectral analysis method. The formula can reflect the analytical relationship between gravity field measurement performance and system parameters such as orbit altitude, the inner-satellite orbit determination error, the inner-satellite residual disturbances, data sampling interval and total measurement time. This analytical formula was then corrected by four factors introduced from numerical simulation of IFS gravity field measurement. By comparing computation results from corrected analytical formula and the actual gravity field measurement performance by CHAMP, the correctness and rationality of this analytical formula were verified. Based on this analytical formula, the influences of system parameters on IFS gravity field measurement were analyzed. It is known that gravity field measurement performance is a monotone decreasing function of orbit altitude, the inner-satellite orbit determination error, the inner-satellite residual disturbances, data sampling interval and the reciprocal of total measurement time. There is a match relationship between the inner-satellite orbit determination error and residual disturbances, in other words, the change rate of gravity field measurement performance with one of them is seriously restricted by their relative size. The analytical formula can be used to quantitatively evaluate gravity field measurement performance fast and design IFS parameters optimally. It is noted that the analytical formula and corresponding conclusions are applied to any gravity satellite which measures gravity field by satellite perturbation orbit.     

燃烧室燃烧与排放特性试验与数值计算

为了探寻燃烧室进口空气温度、压力以及油气比对点熄火边界、温升、燃烧效率以及主要排放物摩尔分数的影响规律， 对航空发动机燃烧室在多工况下的点熄火特性、出口温度分布与主要排放物摩尔分数进行了试验测试。分别采用正癸烷的简化 反应机理与C 12 H 23 燃料的单步反应机理，对该燃烧室火焰筒内流场结构、温度场、中间组分与主要排放物摩尔分数分布特性进行了 数值计算，并与相应试验数据进行了对比分析。结果表明：随着燃烧室进口空气温度、压力以及油气比的提高，燃烧室燃烧效率、 温升、出口平均温度与NO X 摩尔分数逐渐提高，而UHC与CO摩尔分数逐渐降低；与采用C 12 H 23 燃料单步反应机理相比，采用正癸 烷的简化反应机理计算得到的火焰筒内流场与温度场分布更为合理，火焰筒出口温度场分布以及主要排放物摩尔分数与相应试 验数据更为接近，计算精度得到较大提高。     

基于DLMS技术粉末烧结参数优化控制系统分析

从激光系统、扫描系统、粉末系统对直接激光金属烧结参数进行了分析,数值模拟了金属粉末烧结温度场,并结合γ'相析出强化相强化机理分析,建立了烧结参数优化控制模型,为烧结参数优化提供了理论基础;在此基础上提出了实时性烧结参数优化控制系统的雏形.     

飞机战伤抢修评估与设计方法综述

飞机战伤抢修（ABDR）是提高飞机生存力与作战能力的重要手段之一，开展战伤抢修技术研究覆盖飞机全寿命阶段。回顾了战伤抢修研究的历史和现状，分别从战伤评估、战伤抢修设计、战场维修与保障等3方面总结了战伤抢修体系要点，重点综述了战伤抢修预评估技术、战伤现场评估技术、战伤抢修设计准则与原则、战伤抢修设计与评价方法、战场快速维修技术、战场保障方法等方面的理论与研究进展。在此基础上，针对未来体系对抗与智能化作战环境，结合目前战伤抢修需求，提出了包括先进材料结构飞机战伤抢修技术、直升机战伤抢修技术、飞机战伤评估智能技术等战伤抢修技术研究需要关注和解决的问题。     

近区场强仪自动校准测试的研究

介绍了近区场强仪的校准原理和方法，着重介绍了近区场强仪的自动校准测试系统和软件的研究。     

Monitoring the South Atlantic Anomaly using ATSR instrument series

The South Atlantic Anomaly (SAA) has been monitored for 19 years using the Along Track Scanning Radiometer (ATSR) series of instruments onboard the ERS-1, ERS-2 and ENVISAT ESA satellites. The time evolution of the night-time particle induced noise in the short wavelength infrared (SWIR, 1.6 μm) and visible (VIS, 0.55 μm) channels of the ATSR instrument series have been analysed. The monthly location and extension of the SAA are inferred by fitting a two-dimensional, elliptical Gaussian function to the coordinates of the night-time hot spots detected over the SAA region. The location of the centre of the SAA is found to drift westwards with an average drift rate of about 0.24 deg/year and northward with an average drift rate of about 0.12 deg/year. Irregularities are found where the drift speed is inverted and the SAA moves eastward and southward. Results indicate that, as expected, the retrieved values of SAA’s strength and extension are anti-correlated with the solar activity expressed by the solar flux at 10.7 cm (F10.7). Finally, the peak-to-peak amplitude of the seasonal variation of the SAA strength, estimated from monthly VIS data, is found to be 30% of the average value with the annual to semiannual amplitude ratio of 1.38.