Journey into space

James Machell, Chris Tallon and Dan Hedges outline the particular objectives and achievements of the Bradford Robotic Telescope.     

我国空间物理研究进展

经过多年的建设与努力,我国日地空间物理与空间天气领域的研究呈现蓬勃的发展态势.《地球物理学报》以空间物理为专辑,集中在2014年11期刊发38篇文章,涵盖了基于"子午工程"观测数据分析在内的空间物理和空间天气方面的一批最新研究成果.这些工作涉及电离层、中高层大气、地磁与磁层、太阳及太阳风等学科方向,还有两篇工作涉及行星空间环境.本文将从这五个学科方向简要地介绍收入专辑的这些工作.     

Ionospheric space weather effects monitored by simultaneous ground and space based GNSS signals

Ionospheric space weather effects can degrade the performance of global navigation satellite systems (GNSS), i.e. their accuracy, reliability and availability. However, well established ground based and innovative space based GNSS measurements offer the unique chance for a permanent monitoring of the electron density structure of the global ionosphere–plasmasphere system. In this paper we review various types of perturbations in the ionospheric plasma density and distribution. In order to analyze these space weather effects we use 30 s sampled measurements provided by the global GPS ground tracking network of the IGS. Furthermore, to get a more comprehensive view on the perturbations analyzed also are simultaneously obtained GPS measurements onboard the LEO satellite CHAMP (challenging minisatellite payload). Whereas the ground based measurements show strong horizontal redistribution of plasma during ionospheric storms, the space-borne measurements indicate a severe vertical redistribution of the ionospheric plasma during the selected events. The role of the various dynamical forces such as meridional winds and electric fields is also discussed.     

A layered micropolar half space

Summary Wave propagation in a semi-infinite micropolar isotropic elastic solid lying over another micropolar isotropic elastic solid is considered using the theory of micropolar elasticity initiated byEringen [3]²). The relation between the group velocity and the speed of propagation is obtained for the new type of surface wave.     

Plate tectonics in ω space

The relative angular velocity vectors of the plates covering the earth form a three-dimensional closed polyhedron, for which we propose the name geohedron. All forms of plate evolution produce simple changes in the geohedron. Corresponding bodies exist for relative angular accelerations and an attempt is made to determine the value of the relative accelerations of the plates forming a single triple junction when they are governed by kinematic effects alone, but the resulting values do not agree with the available observations.     

Large molecules in space?

Dust, atoms and a few, small, molecules are known to exist in interstellar space. David Williams wonders whether bigger molecules exist around or between the stars, and what their presence would imply.     

On the evaluation of space networks

Резюме Описан способ определения координат точек земной поверхности на основе измерения одного базиса, горизонтальных и вертикальных углов (принципиальная возможность решения этой задачи выяснена Молоденским в 1949 г.). Предварительные значения координат и элементов ориентирования местных координатных систем при уравнивании пространственных сетей рекомендовано определять по необходимым измерениям. Приведены дифференциалные формулы геодезических и астрономических азимутов и зенитных расстояний.

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Address: Verchnjaja Pervomajskaja 4b, Moskva E-264, USSR.     

Nongyrotropic particle distributions in space plasmas

In nonstationary, strong inhomogeneous or open plasmas particle orbits are rather complicated. If the nonstationary time scale is smaller than the gyration period, if the inhomogeneity scale is smaller than the gyration radius, i.e. at magnetic plasma boundaries, or if the plasma has sources and sinks in phase space, then nongyrotropic distribution functions occur. The stability of such plasma configurations is studied in the framework of linear dispersion theory. In an open plasma nongyrotropy drives unstable waves parallel and perpendicular to the background magnetic field, whereas in the gyrotropic limit the plasma is stable. In nonstationary plasmas nongyrotropy drives perpendicular unstable waves only. Temporal modulation couples a seed mode with its side lobes and thus it renders unstable wave growth more difficult. As an example of an inhomogeneous plasma a magnetic halfspace is discussed. In a layer with thickness of the thermal proton gyroradius a nongyrotropic distribution is formed which may excite unstable parallel and perpendicular propagating waves.     

Ionospheric research and space weather services

This paper concentrates on those major areas where our current physical understanding and recent advances can lead to positive predictions of the expected effects of ionospheric activity on the near-Earth space environment and on technological systems which operate within this environment. It briefly describes some of the key links between solar activity and the various physical processes, which govern ionospheric plasma structure that has been under scientific examination over past several decades but has lately received significant importance in relation to the space weather services. Specific examples during extremely intense solar event show how ionospheric monitoring techniques that have contributed immense data sets and related empirical and theoretical formulations have been incorporated in different ionospheric specification and prediction models for real-time operational applications. Finally, the general question of what might be expected as a result of current activities within different European cooperative projects is addressed.     

地球和空间的磁场监测

有了地磁观测台站的数据,地球物理学家即使不离开地面也可以洞察我们这颗行星的内部情况以及近地空间的环境。     

Ionospheric correction of space radar data

Radar is a critical tool for maintaining knowledge of the many objects in low Earth orbit and thus for maintaining confidence that societies around the world are secure against a variety of space-based threats. It is therefore important to raise awareness that LEO objects are embedded in the envelope of relatively dense plasma that co-rotates with the Earth (ionosphere-plasmasphere system) and thus accurate tracking must correct for the group delay and refraction caused by that system. This paper seeks to promote that awareness by reviewing those effects and high-lighting key issues: the need to customise correction to the altitude of the tracked object and prevailing space weather conditions, that ionospheric correction may be particularly important as an object approaches reentry. The paper outlines research approaches that should lead to better techniques for ionospheric correction and shows how these might be pursued in the context of the EURIPOS initiative.     

中国空间天气研究进展

空间天气指太阳、行星际空间和地球空间(地球磁层、电离层、热层和中高层大气)的状态及其变化,它能够影响到天基和地基技术系统的运行和可靠性,危及人类的生存.空间天气计划包括观测和资料分析,研究和数值建模,预报和服务.本文评述了近十年来我国空间天气研究中的一些重要成果.     

Kristian Birkeland: The first space scientist

More than one hundred years ago Kristian Birkeland (1867–1917) first addressed the question as to why auroras appear overhead when the Earth's magnetic field is disturbed. He laid foundations for our current understanding of geomagnetism and polar auroras. For the first time cosmic phenomena were scaled and simulated in a laboratory. Birkeland's terrella experiments were ingenious. Even though the famous Lord Kelvin, in 1892, wrote that no matter passes between the Sun and the Earth, Birkeland's first auroral theory from 1896 is based on charged particle of solar origin, illustrated by the following quotation: “the auroras are formed by corpuscular rays drawn in from space, and coming from the sun”. Thus, the year 1896 marks the founding of space plasma physics. His most enduring contribution to auroral physics was his recognition that field-aligned currents are needed to couple auroral phenomena in the upper atmosphere to interplanetary space. The existence of field-aligned currents was controversial and disputed vigorously among scientists for more than 50 years. During The Birkeland Symposium in 1967 it was unanimously proposed that field-aligned currents in space should be called “Birkeland currents”, which was accepted by the International Union for Geomagnetism and Aeronomy. Today, plasma physicists strongly believe that many significant cosmic phenomena result from streams of Birkeland currents.     

A simple formula for interpolation inn-dimensional space

n¶rt;m u u¶rt; umnu n-a nmam, ma ¶rt;mm n¶rt; u (auum m um ¶rt;uam, aum ua¶rt;m umnua uu). ¶rt;a nu¶rt;um nmu u¶rt; ma umnu u m ma.     

The scientific case for human space exploration

Ian Crawford and Charles Cockell report on a wide-ranging RAS Discussion Meeting putting the broad scientific case for people in space, at the Linnean Society on 10 December 2004.     

Native iron in the Earth and space

Thermomagnetic and microprobe studies of native iron in the terrestrial upper-mantle hyperbasites (xenoliths in basalts), Siberian traps, and oceanic basalts are carried out. The results are compared to the previous data on native iron in sediments and meteorites. It is established that in terms of the composition and grain size and shape, the particles of native iron in the terrestrial rocks are close to each other and to the extraterrestrial iron particles from sediments and meteorites. This suggests that the sources of the origin of these particles were similar; i.e., the formation conditions in the Earth were close to the conditions in the meteorites’ parent bodies. This similarity is likely to be due to the homogeneity of the gas and dust cloud at the early stage of the solar system. The predominance of pure native iron in the sediments can probably be accounted for by the fact that interstellar dust is mostly contributed by the upper-mantle material of the planets, whereas the lower-mantle and core material falls on the Earth mainly in the form of meteorites. A model describing the structure of the planets in the solar system from the standpoint of the distribution of native iron and FeNi alloys is proposed.     

Modelling of space weather effects on pipelines

The interaction between the solar wind and the Earth's magnetic field produces time varying currents in the ionosphere and magnetosphere. The currents cause variations of the geomagnetic field at the surface of the earth and induce an electric field which drives currents in oil and gas pipelines and other long conductors. Geomagnetically induced currents (GIC) interfere with electrical surveys of pipelines and possibly contribute to pipeline corrosion.In this paper, we introduce a general method which can be used to determine voltage and current profiles for buried pipelines, when the external geoelectric field and the geometry and electromagnetic properties of the pipeline are known. The method is based on the analogy between pipelines and transmission lines, which makes it possible to use the distributed source transmission line (DSTL) theory. The general equations derived for the current and voltage profiles are applied in special cases. A particular attention is paid to the Finnish natural gas pipeline network.This paper, related to a project about GIC in the Finnish pipeline, thus provides a tool for understanding space weather effects on pipelines. Combined with methods of calculating the geoelectric field during magnetic storms, the results are applicable to forecasting of geomagnetically induced currents and voltages on pipelines in the future.