Science objectives of the magnetic field experiment onboard Aditya-L1 spacecraft

The Aditya-L1 is first Indian solar mission scheduled to be placed in a halo orbit around the first Lagrangian point (L1) of Sun-Earth system in the year 2018–19. The approved scientific payloads onboard Aditya-L1 spacecraft includes a Fluxgate Digital Magnetometer (FGM) to measure the local magnetic field which is necessary to supplement the outcome of other scientific experiments onboard. The in-situ vector magnetic field data at L1 is essential for better understanding of the data provided by the particle and plasma analysis experiments, onboard Aditya-L1 mission. Also, the dynamics of Coronal Mass Ejections (CMEs) can be better understood with the help of in-situ magnetic field data at the L1 point region. This data will also serve as crucial input for the short lead-time space weather forecasting models.The proposed FGM is a dual range magnetic sensor on a 6?m long boom mounted on the Sun viewing panel deck and configured to deploy along the negative roll direction of the spacecraft. Two sets of sensors (tri-axial each) are proposed to be mounted, one at the tip of boom (6?m from the spacecraft) and other, midway (3?m from the spacecraft). The main science objective of this experiment is to measure the magnitude and nature of the interplanetary magnetic field (IMF) locally and to study the disturbed magnetic conditions and extreme solar events by detecting the CME from Sun as a transient event. The proposed secondary science objectives are to study the impact of interplanetary structures and shock solar wind interaction on geo-space environment and to detect low frequency plasma waves emanating from the solar corona at L1 point. This will provide a better understanding on how the Sun affects interplanetary space.In this paper, we shall give the main scientific objectives of the magnetic field experiment and brief technical details of the FGM onboard Aditya-1 spacecraft.     

Integrated supersonic wind tunnel nozzle

In supersonic wind tunnels, the airflow at the exit of a convergent-divergent nozzle is affected by the connection between the nozzle and test section, because the connection is a source of disturbance for supersonic flow and the source of disturbance generated by this disturbance propagates downstream. In order to avoid the disturbance, the test can only be carried out in the rhombus area. However, for the supersonic nozzle, the rhombus region is small, limiting the size and attitude angle of the test model. An integrated supersonic nozzle is a nozzle and a test section as a whole, which is designed to weaken or eliminate the disturbance. The inviscid contour of the supersonic nozzle is based on the method of characteristics. A new curve is formed by the smooth connection between the inviscid contour and test section, and the boundary layer is corrected for the overall curve. Integrated supersonic nozzles with Mach number 1.5 and 2 are designed, which are based on this method. The flow field is validated by numerical and experimental results. The results of the study highlight the importance of the connection about the nozzle outlet and test section. They clearly show that the wave system does not exist at the exit of the supersonic nozzle, and the flow field is uniform throughout the test section.     

CMEs and active regions on the sun

The relationship between active regions (ARs) and coronal mass ejections (CMEs) is studied. For this purpose a statistical analysis of 694 CMEs associated with ARs was carried out. We considered the relationship between properties of the CMEs and ARs characterized using the McIntosh classification. We demonstrated that CMEs are likely to be launched from ARs in the mature phase of their evolution when they have complex magnetic field. The fastest and halo CMEs can be ejected only from the most complex ARs (when an AR is a bipolar group of spots with large asymmetric penumbras around the main spot with many smaller spots in the group). We also showed that the wider events have a tendency to originate from uncomplicated magnetic structures. This tendency was used for estimation of the real angular widths of the halo CMEs. The probability of launching of fast CMEs increases together with increase of the complexity and size of ARs. The widest, but slow, CMEs originate from the simplest magnetic structure which are still able to produce CMEs. Our results could be useful for forecasting of space weather.     

Cut-off features in interplanetary solar radio type IV emission

Solar radio type IV bursts can sometimes show directivity, so that no burst is observed when the source region in located far from the solar disk center. This has recently been verified also from space observations, at decameter wavelengths, using a 3D-view to the Sun with STEREO and Wind satellites. It is unclear whether the directivity is caused by the emission mechanism, by reduced radio wave formation toward certain directions, or by absorption/blocking of radio waves along the line of sight. We present here observations of three type IV burst events that occurred on 23, 25, and 29 July 2004, and originated from the same active region. The source location of the first event was near the solar disk center and in the third event near the west limb. Our analysis shows that in the last two events the type IV bursts experienced partial cut-offs in their emission, that coincided with the appearance of shock-related type II bursts. The type II bursts were formed at the flanks and leading fronts of propagating coronal mass ejections (CMEs). These events support the suggestion of absorption toward directions where the type II shock regions are located.     

二次燃烧对自力弹射内弹道影响分析

目前弹射所用低温药柱的燃烧平衡产物中含有可燃气体成分,遇初容室内氧气后发生二次燃烧,影响初容室内流场与弹射内弹道特性。为了分析二次燃烧对自力弹射方案内弹道的影响,建立了自力弹射可压缩流动仿真模型,结合有限速率化学反应模型与动网格技术,利用PISO(压力隐式算子分裂法)算法对控制方程进行数值求解。计算结果表明,二次燃烧使得初容室初始压力峰值时刻提前,并影响初始压力峰值大小。仿真分析结果为自力弹射内弹道设计提供了理论参考。     

PROGRESS IN HELIOSPHERIC PHYSICS

This is an overview of progresses in heliospheric physics made in China in the period of June, 2000 to May, 2002. The report is focused on theoretical studies,modelling and observational analysis of interplanetary physical phenomena, and consists of five sections: the acceleration and heating of the solar wind, corona structures, coronal mass ejections, magnetic reconnection phenomena, and in terplanetary transient phenomena. The main achievements made recently by Chinese scientists in related areas are simply listed in corresponding sections without any priority, only certain editorial consideration.     

采用流动控制的超声速内埋物投放特性研究

针对马赫数Ma3飞行状态下的内埋物安全投放难题,提出了两种适用于非平坦舱体外形的超声速内埋物投放分离过程的流动控制方法:第一种方法采用了圆棒扰流器,第二种方法采用气帘喷流。为了验证两种不同流动控制方法的效果,引入结构嵌套六自由度动态网格技术和基于k-ω湍流模型的Navier-Stokes方程计算,对包括重力投放、弹射投放、采用圆棒扰流器的重力投放和采用气帘的重力投放等4种不同的投放分离状态进行了动态全过程的计算对比分析。通过对仿真计算结果分析发现,当来流马赫数Ma∞3时,采用流动控制的投放物分离运动特性产生了明显的变化。由投放物下落过程中的俯仰偏航特性可以得出:采用圆棒流动控制有利于安全分离;气帘流动控制具有应用潜力,但采用这种方法需要针对特定的投放条件进行优化,否则可能诱发投放物在俯仰方向的姿态发散。     

NUMERICAL STUDY OF TOPOLOGICAL STRUCTURE OF 3-D TRANSONIC VISCOUS FLOW FIELD (TVFF) INSIDE TURBINE CASCADE

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Heliosphereic Physics Research in China:2002-2003

This brief report summarized the latest advances of the heliospheric physics research in China during the period of 2002-2003, made independently by Chinese space physicists and through international collaboration. The report covers all aspects of the heliospheric physics, including theoretical studies, numerical simulation and data analysis.     

超声速火箭橇全程速度雷达测试方法

针对超声速侵彻类火箭橇试验的全程速度测试难题, 提出了多台雷达来向 与去向结合的接力测试方案, 并阐述了实现该方案需解决的关键技术及解决途径, 包 括：高精度同步与远端控制装置设计和多台雷达数据融合处理,最后通过试验对该方法 进行了原理验证,验证结果满足要求。