太空行走100问（十四）

太空行走风险(上) 80.航天员在太空行走中可能会遇到哪些风险? (1)太空环境因素方面的风险: ①宇宙辐射 在近地空间的宇宙辐射属于电离辐射,主要有三个来源:地球辐射带、银河宇宙线和太阳粒子事件.     

太阳活动突发过程对临近空间大气影响的模拟

空间天气对地球及近地空间具有重要影响,大的空间天气事件对中上层大气动力学和成分具有不同的影响。利用全大气耦合模式WACCM,针对太阳耀斑、太阳质子、地磁暴三类事件,以太阳活动平静期2015年5月10-14日的GEOS-5数据为模式背景场,通过F_10.7、离子产生率、Kp及Ap指数设置,分别模拟三类事件对临近空间大气温度、密度和臭氧的影响。结果表明耀斑事件在三类事件中对临近空间大气温度和密度的影响最为显著。平流层大气温度增加是由耀斑辐射增强引起平流层臭氧吸收紫外辐射发生的光化学反应所致,耀斑事件引起平流层和低热层温度增加约为2～3 K,低热层大气相对密度增加在6%以内;太阳质子事件及磁暴事件主要影响低热层,但太阳质子事件和磁暴事件对低热层温度扰动不大于1 K。     

“奥伯斯佯谬”解析

所谓的“奥伯斯佯谬”,即浩瀚的宇宙有无数的恒星,大多数比太阳还大、还热,甚至比太阳大千倍万倍,论年龄大多超过太阳的60亿年,它们从无间歇地向四面八方辐射光和热.但是如此长的年月竟不能使漆黑的宇宙变白,仅能使宇宙增温2.7K.但是地球上的光和热确实来自太阳的辐射,这难以被人们理解的现象,后来被称为“奥伯斯佯谬”.     

宇宙探索十四、微波背景辐射和宇宙大爆炸

微波背景辐射的发现发现微波背景辐射,是射电望远镜早期探测的重大成果,它与发现脉冲星一样,非常具有戏剧性。乔治·伽莫夫在1948年预言,早期的宇宙必须是非常密集的、白热的,会产生黑体辐射。由于宇宙膨胀,这种辐射的温度已降至5K,即绝对零度以上5度。20世纪60年代初,两位美国     

“普朗克”卫星首次绘出宇宙之光

<正>7月5日,在意大利都灵市举行的一场新闻发布会上,欧洲空间局公布了去年发射的"普朗克"探测卫星拍摄的首幅宇宙微波背景辐射的全景图。宇宙微波背景辐射代表了在宇宙大爆炸之后,随着宇宙的冷却,与物质密切相关的第一批逃逸的光子,也被喻为宇宙的第一束光线。宇宙微波背景辐射经过137亿年的漫长旅行才到达地球,对研究人     

空间甚低频太阳射电Ⅲ型爆研究进展

太阳非热高能粒子流是产生灾害性空间天气事件最主要的驱动源之一,其主要观测特征是具有快速频率漂移特征的射电Ⅲ型爆.主要介绍了国际上在空间甚低频波段(<30 MHz)太阳射电Ⅲ型爆的主要观测设备和研究进展,包括具备高时间–频率分辨能力的空间和月基甚低频频谱仪等,对存在的主要问题进行了详细讨论,系统分析了空间甚低频射电探测器...     

沿着COBE的轨迹

宇宙是始于一次“大爆炸”吗 ?若如此，这一爆炸是什么样子 ?它是均匀地膨胀还是脉动性地进行 ?星系是如何聚集成形的 ?这些都是天文界有待解决的最基本问题。 20世纪 80年代末，美国航空航天局发射出一颗天文卫星——“宇宙背景探测者 (COBE)”，对太空进行观测，寻找并记录原始大爆炸所留下的 遗迹。 　　COBE绘出宇宙的微波背景和红外背景。微波背景辐射被认为是原始大爆炸的残迹，它来自空间的各个方向，几乎是均匀的，其能量相当于 2 7K的温度。 COBE以空前的精度和灵敏性来测量这一辐射。它还寻找天文学家所预言的，但一直…     

日先驱者号探测器绕地球变轨获得成功

1985年1月8日从宇宙科学研究所鹿儿岛宇宙空间观测所发射的先驱(MS-T5)哈雷彗星探测器,于1986年3月11日到达约700万km处接近哈雷彗星,在取得珍贵的观测数据之后绕太阳运行轨道继续航行。先驱探测器上搭载的探测行星间磁场、等离子体波动、太阳风的3种科学观测仪器,都工作正常。宇宙科学研究所将1990年1月24日发射的飞天工程实验卫星绕行星变轨技术,应用到先驱探测器上,即1992年1月8日,通过地球引力场改变先驱探测器轨道。     

空间太阳物理学科发展战略研究

太阳物理学是研究太阳上发生的物理过程及其对行星际空间环境影响的学科。太阳是人类唯一可以进行细致探测的恒星，也是天然的多尺度过程并存的等离子体实验室，同时，太阳活动直接影响日地空间环境和人类地球家园的宜居性，剧烈的太阳活动如耀斑和日冕物质抛射还会影响人类的航天航空、通信导航、电网等高技术活动与设施。因此对太阳物理的研究不仅是理解浩瀚宇宙的基石，也是理解日地联系和行星宜居性的基础，同时还是国家在航天和空间安全领域的战略需求。21世纪以来，随着卫星探测技术发展，太阳物理学进入了全新的发展阶段。本文梳理了近年来太阳物理学在空间探测中的发展态势，凝练中国太阳物理学未来空间探测发展的重点领域，优化学科布局，推进太阳物理的高质量发展。     

追踪宇宙第一道光"新一代太空望远镜"

□□研究宇宙的起源与演化是天文学的重要任务之一。20世纪中叶,一些著名的天文学家认为,宇宙起源于(137±2)亿年前的一次大爆炸,大爆炸后,整个宇宙不断地膨胀,星系整体退行。各个方向上的星系都在飞快地离地球远去。 由于多普勒效应,地球上接收到离其远去的星系发射的电磁波,频率会降低,也就是发射光谱向长波(红光)方向移动,天文学上称之为“红移”。离地球越远的星系,退行速度越大,产生的红移越大。遥远的、退行中的恒星、星系和类星体等天体发射的光本是可见光和紫外辐射,由于红移,地球上探测接收到的大多是红外辐射。所以,利用红外探测,…     

Evolution of Dst index,cosmic rays and global temperature during solar cycles 20–23

We have studied conditions in interplanetary space, which can have an influence on galactic cosmic ray (CR) and climate change. In this connection the solar wind and interplanetary magnetic field parameters and cosmic ray variations have been compared with geomagnetic activity represented by the equatorial Dst index from the beginning 1965 to the end of 2012. Dst index is commonly used as the solar wind–magnetosphere–ionosphere interaction characteristic. The important drivers in interplanetary medium which have effect on cosmic rays as CMEs (coronal mass ejections) and CIRs (corotating interaction regions) undergo very strong changes during their propagation to the Earth. Because of this CMEs, coronal holes and the solar spot numbers (SSN) do not adequately reflect peculiarities concerned with the solar wind arrival to 1 AU. Therefore, the geomagnetic indices have some inestimable advantage as continuous series other the irregular solar wind measurements. We have compared the yearly average variations of Dst index and the solar wind parameters with cosmic ray data from Moscow, Climax, and Haleakala neutron monitors during the solar cycles 20–23. The descending phases of these solar cycles (CSs) had the long-lasting solar wind high speed streams occurred frequently and were the primary contributors to the recurrent Dst variations. They also had effects on cosmic rays variations. We show that long-term Dst variations in these solar cycles were correlated with the cosmic ray count rate and can be used for study of CR variations. Global temperature variations in connection with evolution of Dst index and CR variations is discussed.     

23rd solar cycle: Solar activity parameters and associated Forbush decreases

We report Forbush decreases (FD) in cosmic ray intensity from January 1996 to December 2008, the whole Solar Cycle 23rd. Statistical analysis is done for only 152 events for which associated solar flare position, flare classes, and Coronal Mass Ejections (CME) speed are given. We applied FD parameters taken from the Forbush Effects and Interplanetary Disturbances databases maintained by the Pushkov Institute of Terrestrial Magnetism, Ionosphere, and Radiowave Propagation (IZMIRAN), obtained by processing the data of the worldwide neutron monitor network using the global survey method (GSM) (A. Belov et al., 2018). For the said number of events, we examine their effect on interplanetary space and the decrease of the galactic cosmic rays (GCR) near Earth. We found that the 11–20° latitudinal belt shows more FD- associated flare events than the other latitudinal belts, and on this belt, the Southern hemisphere is more active. The results reveal that FDs and solar flares are well correlated. Statistical analysis is carried out for the magnitude of the CR decrease with solar and geomagnetic parameters.     

The dynamic heliosphere,solar activity,and cosmic rays

This brief review addresses the relation between solar activity, cosmic ray variations and the dynamics of the heliosphere. The global features of the heliosphere influence what happens inside its boundaries on a variety of time-scales. Galactic and anomalous cosmic rays are the messengers that convey vital information on global heliospheric changes in the manner that they respond to these changes. By observing cosmic rays over a large range of energies at Earth, and with various space detectors, a better understanding is gained about space weather and climate. The causes of the cosmic ray variability are reviewed, with emphasis on the 11-year and 22-year cycles, step modulation, charge-sign dependent modulation and particle drifts. Advances in this field are selectively discussed in the context of what still are some of the important uncertainties and outstanding issues.     

Neutron monitor asymptotic directions of viewing during the event of 13 December 2006

During the recent ground level enhancement of 13 December 2006, also known as GLE70, solar cosmic ray particles of energy bigger that ∼500 MeV/nucleon propagated inside the Earth’s magnetosphere and finally accessed low-altitude satellites and ground level neutron monitors. The magnitude and the characteristics of this event registered at different neutron monitor stations of the worldwide network can be interpreted adequately on the basis of an estimation of the solar particle trajectories in the near Earth interplanetary space. In this work, an extended representation of the Earth’s magnetic field was realized applying the Tsyganenko 1989 model. Using a numerical back-tracing technique the solar proton trajectories inside the magnetospheric field of the Earth were calculated for a variety of particles, initializing their travel at different locations, covering a wide range of energies. In this way, the asymptotic directions of viewing were calculated for a significant number of neutron monitor stations, providing crucial information on the Earth’s “magnetospheric optics” for primary solar cosmic rays, on the top of the atmosphere, during the big solar event of December 2006. The neutron monitor network has been treated, therefore, as a multidimensional tool that gives insights into the arrival directions of solar cosmic ray particles as well as their spatial and energy distributions during extreme solar events.     

Space storm measurements of the July 2005 solar extreme events from the low corona to the Earth

The Athens Neutron Monitor Data Processing (ANMODAP) Center recorded an unusual Forbush decrease with a sharp enhancement of cosmic ray intensity right after the main phase of the Forbush decrease on 16 July 2005, followed by a second decrease within less than 12 h. This exceptional event is neither a ground level enhancement nor a geomagnetic effect in cosmic rays. It rather appears as the effect of a special structure of interplanetary disturbances originating from a group of coronal mass ejections (CMEs) in the 13–14 July 2005 period. The initiation of the CMEs was accompanied by type IV radio bursts and intense solar flares (SFs) on the west solar limb (AR 786); this group of energetic phenomena appears under the label of Solar Extreme Events of July 2005. We study the characteristics of these events using combined data from Earth (the ARTEMIS IV radioheliograph, the Athens Neutron Monitor (ANMODAP)), space (WIND/WAVES) and data archives. We propose an interpretation of the unusual Forbush profile in terms of a magnetic structure and a succession of interplanetary shocks interacting with the magnetosphere.     

Solar cosmic rays as a specific source of radiation risk during piloted space flight.

Solar cosmic rays present one of several radiation sources that are unique to space flight. Under ground conditions the exposure to individuals has a controlled form and radiation risk occurs as stochastic radiobiological effects. Existence of solar cosmic rays in space leads to a stochastic mode of radiation environment as a result of which any radiobiological consequences of exposure to solar cosmic rays during the flight will be probabilistic values. In this case, the hazard of deterministic effects should also be expressed in radiation risk values. The main deterministic effect under space conditions is radiation sickness. The best dosimetric functional for its analysis is the blood forming organs dose equivalent but not an effective dose. In addition, the repair processes in red bone marrow affect strongly on the manifestation of this pathology and they must be taken into account for radiation risk assessment. A method for taking into account the mentioned above peculiarities for the solar cosmic rays radiation risk assessment during the interplanetary flights is given in the report. It is shown that radiation risk of deterministic effects defined, as the death probability caused by radiation sickness due to acute solar cosmic rays exposure, can be comparable to risk of stochastic effects. Its value decreases strongly because of the fractional mode of exposure during the orbital movement of the spacecraft. On the contrary, during the interplanetary flight, radiation risk of deterministic effects increases significantly because of the residual component of the blood forming organs dose from previous solar proton events. The noted quality of radiation responses must be taken into account for estimating radiation hazard in space.     

The influence of interplanetary shocks on solar protons measured in the stratosphere.

Since the beginning of the 22nd solar cycle twenty solar proton events were observed by the regular balloon measurements of cosmic rays. Temporal changes of intensities and energy spectra of solar protons with energy 100-500 MeV were obtained. The strong influence of interplanetary shock waves on the proton flux characteristics near the Earth was observed. Possible effects of solar proton transport in the vicinity of shock fronts are discussed to explain the observational data.     

Extrasolar space exploration by a solar sail accelerated via thermal desorption of coating

For extrasolar space exploration it might be very convenient to take advantage of space environmental effects such as solar radiation heating to accelerate a solar sail coated by materials that undergo thermal desorption at a particular temperature. Thermal desorption can provide additional thrust as heating liberates atoms, embedded on the surface of the solar sail. We are considering orbital dynamics of a solar sail coated with materials that undergo thermal desorption at a specific temperature, as a result of heating by solar radiation at a particular heliocentric distance, and focus on two scenarios that only differ in the way the sail approaches the Sun. For each scenario once the perihelion is reached, the sail coat undergoes thermal desorption. When the desorption process ends, the sail then escapes the Solar System having the conventional acceleration due to solar radiation pressure. We study the dependence of a cruise speed of a solar sail on perihelion of the orbit where the solar sail is deployed. The following scenarios are considered and analyzed: (1) Hohmann transfer plus thermal desorption. In this scenario the sail would be carried as a payload to the perihelion with a conventional propulsion system by a Hohmann transfer from Earth’s orbit to an orbit very close to the Sun and then be deployed. Our calculations show that the cruise speed of the solar sail varies from 173?km/s to 325?km/s that corresponds to perihelion 0.3?AU and 0.1 AU, respectively. (2) Elliptical transfer plus Slingshot plus thermal desorption. In this scenario the transfer occurs from Earth’s orbit to Jupiter’s orbit; then a Jupiter’s fly-by leads to the orbit close to the Sun, where the sail is deployed and thermal desorption comes active. In this case the cruise speed of the solar sail varies from 187?km/s to 331?km/s depending on the perihelion of the orbit. Our study analyses and compares the different scenarios in which thermal desorption comes beside traditional propulsion systems for extrasolar space exploration.