Real-time global MHD simulation of the solar wind interaction with the earth’s magnetosphere

We have developed a real-time global MHD (magnetohydrodynamics) simulation of the solar wind interaction with the earth’s magnetosphere. By adopting the real-time solar wind parameters and interplanetary magnetic field (IMF) observed routinely by the ACE (Advanced Composition Explorer) spacecraft, responses of the magnetosphere are calculated with MHD code. The simulation is carried out routinely on the super computer system at National Institute of Information and Communications Technology (NICT), Japan. The visualized images of the magnetic field lines around the earth, pressure distribution on the meridian plane, and the conductivity of the polar ionosphere, can be referred to on the web site (http://www2.nict.go.jp/y/y223/simulation/realtime/).The results show that various magnetospheric activities are almost reproduced qualitatively. They also give us information how geomagnetic disturbances develop in the magnetosphere in relation with the ionosphere. From the viewpoint of space weather, the real-time simulation helps us to understand the whole image in the current condition of the magnetosphere. To evaluate the simulation results, we compare the AE indices derived from the simulation and observations. The simulation and observation agree well for quiet days and isolated substorm cases in general.     

Towards a scientific understanding of the risk from extreme space weather

Like all natural hazards, space weather exhibits occasional extreme events over timescales of decades to centuries. Historical events provoked much interest, and sometimes alarm, because bright aurora becomes visible at mid-latitudes. However, they had little economic impact because the major technologies of those eras were not sensitive to space weather. This is no longer true. The widespread adoption of advanced technological infrastructures over the past 40 years has created significant sensitivity. So these events now have the potential to disrupt those infrastructures – and thus have profound economic and societal impact. However, like all extreme hazards, such events are rare, so we have limited data on which to build our understanding of the events. This limitation is uniquely serious for space weather since it is a global phenomenon. Many other natural hazards (e.g. flash floods) are highly localised, so statistically significant datasets can be assembled by combining data from independent instances of the hazard recorded over a few decades. Such datasets are the foundation on which reliable risk assessment methodologies are built. But we have a single instance of space weather so we would have to make observations for many centuries in order to build a statistically significant dataset. We show that it is not practicable to assess the risk from extreme events using simple statistical methods. Instead we must exploit our knowledge of solar-terrestrial physics to find other ways to assess these risks. We discuss three alternative approaches: (a) use of proxy data, (b) studies of other solar systems, and (c) use of physics-based modelling. We note that the proxy data approach is already well-established as a technique for assessing the long-term risk from radiation storms, but does not yet provide any means to assess the risk from severe geomagnetic storms. This latter risk is more suited to the other approaches, but significant research is needed to make progress. We need to develop and expand techniques to monitoring key space weather features in other solar systems (stellar flares, radio emissions from planetary aurorae). And to make progress in modelling severe space weather, we need to focus on the physics that controls severe geomagnetic storms, e.g. how can dayside and tail reconnection be modulated to expand the region of open flux to envelop mid-latitudes?     

A polytropic model for the solar wind

The solar wind fills the heliosphere and is the background medium in which coronal mass ejections propagate. A realistic modelling of the solar wind is therefore essential for space weather research and for reliable predictions. Although the solar wind is highly anisotropic, magnetohydrodynamic (MHD) models are able to reproduce the global, average solar wind characteristics rather well. The modern computer power makes it possible to perform full three dimensional (3D) simulations in domains extending beyond the Earth’s orbit, to include observationally driven boundary conditions, and to implement even more realistic physics in the equations. In general, MHD models for the solar wind often make use of additional source and sink terms in order to mimic the observed solar wind parameters and/or they hide the not-explicitly modelled physical processes in a reduced or variable adiabatic index. Even the models that try to take as much as possible physics into account, still need additional source terms and fine tuning of the parameters in order to produce realistic results. In this paper we present a new and simple polytropic model for the solar wind, incorporating data from the ACE spacecraft to set the model parameters. This approach allows to reproduce the different types of solar wind, where the simulated plasma variables are in good correspondence with the observed solar wind plasma near 1 AU.     

Research Progress of Interplanetary Physics in Mainland China

Significant progress has been made by Chinese scientists in research of interplanetary physics during the recent two years (2018-2020). These achievements are reflected at least in the following aspects:Activities in solar corona and lower solar atmosphere; solar wind and turbulence; filament/prominence, jets, flares, and radio bursts; active regions and solar eruptions; coronal mass ejections and their interplanetary counterparts; other interplanetary structures; space weather prediction methods; magnetic reconnection; Magnetohydrodynamic (MHD) numerical modeling; solar energetic particles, cosmic rays, and Forbush decreases; machine learning methods in space weather and other aspects. More than one hundred and forty papers in the academic journals have been published in these research directions. These fruitful achievements are obtained by Chinese scholars in solar physics and space physics either independently or through international collaborations. They greatly improve people's understanding of solar activities, solar eruptions, the corresponding space weather effects, and the Sun-Earth relations. Here we will give a very brief review on the research progress. However, it must be pointed out that this paper may not completely cover all achievements in this field due to our limited knowledge.      

天基X射线掠入射式成像望远镜发展现状

阐述了太阳X射线成像观测在空间天气预报中的地位和作用，叙述了掠入射式X射线聚焦成像的基本原理，简要介绍了在轨成功运行的天体X射线成像望远镜和太阳X射线成像望远镜的基本设计和技术指标，并介绍了国内正开发研制的专门服务于空间天气预报的太阳X射线成像望远镜基本设计和主要特点．     

Research Progress of Solar Corona and Interplanetary Physics in China: 2010-2012

The scientific objective of solar corona and interplanetary research is the understanding of the various phenomena related to solar activities and their effects on the space environments of the Earth. Great progress has been made in the study of solar corona and interplanetary physics by the Chinese space physics community during the past years. This paper will give a brief report about the latest progress of the corona and interplanetary research in China during the years of 2010?2012. The paper can be divided into the following parts: solar corona and solar wind, CMEICME, magnetic reconnection, energetic particles, space plasma, space weather numerical modeling by 3D SIP-CESE MHD model, space weather prediction methods, and proposed missions. They constitute the abundant content of study for the complicated phenomena that originate from the solar corona, propagate in interplanetary space, and produce geomagnetic disturbances. All these progresses are acquired by the Chinese space physicists, either independently or through international collaborations.      

Somatic embryos of daylily in space

Poor growth and nuclear abnormalities observable in some space-grown plants have been hypothesized as due to a combination of factors such as degree of development, the specific way the plants are grown and the way they experience multiple stresses, some of which are space-specific. Data from a 132-day experiment on ‘Mir’ using embryogenic cell cultures of daylily (Hemerocallis) allow seemingly contradictory evidence from earlier Shuttle missions to be harmonized: a) the more developed an embryo the less likely it is to suffer catastrophic cell stress during growth, whereas the less developed it is, the greater its vulnerability; (b) the extent to which the stress becomes manifest is also dependent on the extent of pre-existing stresses imposed by suboptimal growing conditions; (c) an appropriate, albeit undesirable, ‘stress match’ with other non-equilibrium determinants, much like a ‘tug of war’, can result in genomic variations in space. It is not understood what is/are the feature(s) of the space environment that cause the various cell division perturbations but they have not yet been mimicked on earth. The stress symptoms were found only in space materials and, as predicted, they were most frequently encountered in smaller, less-developed materials grown under non-optimized conditions. It is concluded that, while any substantial deviation from ‘optimum’ can be a ‘stress’, spaceflight subjects vulnerable materials to cell division or DNA-repair stress(es) that appear distinctive, but remain elusive so far. Fastidiously-controlled growing environments must be devised to resolve the matter of direct versus indirect effects of space. On a practical level, it is predicted that adapting plant biotechnologies to space conditions will not be a casual matter.     

Progress of Solar Corona Study in China

Solar corona study is an important aspect of space weather research.In recent years,great achieVements have been acquired on the solar corona study by the space physics group of China.This paper gives a brief outline of these progresses that have been made during 2006--2008.This kind of research includes observational study of the corona,theoretical investigations,statistical analysis based on a large number of data sets,numerical method for MHD modeling,numerical study of space weather events,and prediction methods for the complicated processes originating from the solar corona.Each is given as a separate part in the following.      

Advance of interplanetary physics study in China: 2008—2010

Interplanetary physics study is an important ingredient in space weather research. Considerable progress this aspect has been achieved by the space physics community of China in recent years. This brief report summarizes the latest advances of the interplanetary physics research in China during the period of 2008--2010. This report includes solar corona and solar wind, interplanetary transients, energetic particles, MHD simulation, space plasma, and prediction methods for physical phenomena originating from both solar corona and interplanetary space.      

Space weather center in Japan

Progress in information technology has enabled to collecting data in near real-time. This significantly improves our ability to monitor space weather conditions. We deliver information on near real-time space weather conditions via the internet. We have started two collaborations with space weather users. One is a measurement of geomagnetically induced current (GIC) of power grids in collaboration with a Japanese power company. The other concerns radiation hazards for aircrews. The radiation exposure level for aircrews was been determined by the Japanese government by the end of 2005. The proposed upper limit is 5 mSV a year. We are actively seeking ways to contribute to this subject. Our activities at the Japanese space weather center are reported in this paper.     

Prospective technologies and equipment for sanitary–hygienic measures for life support systems

Creation of optimal sanitary–hygienic conditions is a prerequisite for good health and performance of crews on extended space missions. There is a rich assortment of associated means, methods and equipment developed and experimentally tested in orbital flights. However, over a one-year period a crew of three uses up about 800 kg of ground-supplied wet wipes and towels for personal needs. The degree of closure of life support systems for long-duration orbital flights should be maximized, particularly for interplanetary missions, which exclude any possibility of re-supply. Washing with regenerated water is the ultimate sanitary–hygienic goal. That is why it is so important to design devices for crew bathing during long-term space missions. Investigations showed that regeneration of wash water (WW) using membrane processes (reverse osmosis, nanofiltration etc.), unlike sorption, would not require much additional expendables. A two-stage membrane recovery unit eliminated >85% of permeate from real WW with organic and inorganic selectivity of 82–95%. The two-stage WW recovery unit was tested with artificial and real WW containing detergents available for space crews. Investigations into the ways of doing laundry and drying along with which detergents will be the best fit for space flight are also planned. Testing of a technology for water extraction from used textiles using a conventional period of contact of 1 s or more, showed that the humidity of the outgoing air flow neared 100%. Issues related to designing the next generation of space life support systems should consider the benefits of integrating new sanitary–hygienic technologies, equipment, and methods.     

Effects of geomagnetic activity variations on the physiological and psychological state of functionally healthy humans: Some results of Azerbaijani studies

There are collaborative and cross-disciplinary space weather studies in the Azerbaijan National Academy of Sciences conducted with purposes of revealing possible effects of solar, geomagnetic and cosmic ray variability on certain technological, biological and ecological systems. This paper describes some results of the experimental studies of influence of the periodical and aperiodical changes of geomagnetic activity upon human brain, human health and psycho-emotional state. It also covers the conclusions of studies on influence of violent solar events and severe geomagnetic storms of the solar cycle 23 on the mentioned systems in middle-latitude location. It is experimentally established that weak and moderate geomagnetic storms do not cause significant changes in the brain’s bioelectrical activity and exert only stimulating influence while severe disturbances of geomagnetic conditions cause negative influence, seriously disintegrate brain’s functionality, activate braking processes and amplify the negative emotional background of an individual. It is concluded that geomagnetic disturbances affect mainly emotional and vegetative spheres of human beings while characteristics reflecting personality properties do not undergo significant changes.     

多种观测数据驱动的三维行星际太阳风MHD模拟

三维磁流体力学（MHD）数值模拟是行星际太阳风研究的重要手段.本文发展了一种由多种观测数据驱动的三维行星际太阳风MHD数值模型.模型的计算区域为0.1AU到1AU附近，使用Lax-Friedrich差分格式在六片网格系统中进行数值求解.边界条件中磁场使用GONG台站观测的光球磁图外推获得，密度通过LASCO观测的白光偏振亮度反演得到，速度根据以上两种观测数据并利用一种基于人工神经网络技术（ANN）的方法得到，温度通过自洽方法根据磁场和密度导出.利用该模型模拟了第2062卡灵顿周（CR2062）时期的行星际太阳风，模拟结果显示出丰富的观测特征，并与OMNI以及Ulysses的实际观测值符合得较好.该模型可用于提供接近真实的行星际太阳风，有助于提高空间天气预报的精度.      

一类TVD型组合差分方法及其在磁流体数值计算中的应用

根据太阳风数值模拟的特点，考虑到算法的质量（收敛速度、稳定性、精度等），结合磁流体数值计算的特性，对三维球坐标磁流体动力学（MHD）方程组中的流体部分采用一种修正Lax-Friedrichs差分法而对磁场部分采用MacComack格式，发展了一类快捷的具有TVD特性的组合数值新方法，作为格式的检验，在一维情况下，将其与PPM格式进行了比较，对一维快慢磁流体激波问题得到了与PPM格式精度相同的结果，然后将其诮到定态太阳风的数值模拟上，在不同等离子体β情形下，可得到理想的太阳风定态结构，为今后将此数值模式应用到具有复杂磁场位型或三维直实太阳风暴的数值模拟研究奠定了基础。     

基于CPU/GPU的日冕偏振亮度并行计算模型

三维磁流体力学(MHD)数值模拟是用来研究日冕和太阳风最常用的方法之一, 其中将计算得到的日冕电子数密度转化为日冕偏振亮度(Polarization Brightness, PB)是与观测对比的重要方法. 由于待转换电子数据网格密度、PB数据网格密度和计算模型的复杂度, 使得日冕偏振亮度的计算比较耗时, 利用单CPU计算无法达到近实时转换日冕偏振亮度的要求, 从而影响了数值模拟的验证效率. 本文在CPU/GPU环境下, 利用CUDA编程技术, 提出了一个日冕偏振亮度并行计算模型. 实验结果表明, 该模型比CPU上的串行模型计算速度提高了31.86倍, 达到了近实时模拟与观测数据比对的计算要求.      

Cone model-based SEP event calculations for applications to multipoint observations

The problem of modeling solar energetic particle (SEP) events is important to both space weather research and forecasting, and yet it has seen relatively little progress. Most important SEP events are associated with coronal mass ejections (CMEs) that drive coronal and interplanetary shocks. These shocks can continuously produce accelerated particles from the ambient medium to well beyond 1 AU. This paper describes an effort to model real SEP events using a Center for Integrated Space weather Modeling (CISM) MHD solar wind simulation including a cone model of CMEs to initiate the related shocks. In addition to providing observation-inspired shock geometry and characteristics, this MHD simulation describes the time-dependent observer field line connections to the shock source. As a first approximation, we assume a shock jump-parameterized source strength and spectrum, and that scatter-free transport occurs outside of the shock source, thus emphasizing the role the shock evolution plays in determining the modeled SEP event profile. Three halo CME events on May 12, 1997, November 4, 1997 and December 13, 2006 are used to test the modeling approach. While challenges arise in the identification and characterization of the shocks in the MHD model results, this approach illustrates the importance to SEP event modeling of globally simulating the underlying heliospheric event. The results also suggest the potential utility of such a model for forcasting and for interpretation of separated multipoint measurements such as those expected from the STEREO mission.     

空间天气模式集成可视化演示软件设计

空间天气模式集成是空间天气预报业务化的基础, 空间天气模式集成可视化演示软件系统是其中重要的研究内容之一. 空间天气模式种类繁多, 要素多样, 模型复杂, 且各模式可视化形式及方法具有差异性. 本文综合当前中国空间天气模式的特点, 构建了一套空间天气模式集成可视化演示系统. 该系统兼容性好、可扩展性高, 能够集成当前中国空间天气中大多数模式. 讨论了空间数据管理方法, 基于Visual C++ 软件平台和OpenGL可视化软件模块,以动态加载方式初步实现了多个空间天气模式的可视化集成.      

Different space weather effects in anomalies of the high and low orbital satellites

Preliminary results of the EU INTAS Project 00810, which aims to improve the methods of safeguarding satellites in the Earth’s magnetosphere from the negative effects of the space environment, are presented. Anomaly data from the “Kosmos” series satellites in the period 1971–1999 are combined in one database, together with similar information on other spacecraft. This database contains, beyond the anomaly information, various characteristics of the space weather: geomagnetic activity indices (Ap, AE and Dst), fluxes and fluences of electrons and protons at different energies, high energy cosmic ray variations and other solar, interplanetary and solar wind data. A comparative analysis of the distribution of each of these parameters relative to satellite anomalies was carried out for the total number of anomalies (about 6000 events), and separately for high (5000 events) and low (about 800 events) altitude orbit satellites. No relation was found between low and high altitude satellite anomalies. Daily numbers of satellite anomalies, averaged by a superposed epoch method around sudden storm commencements and proton event onsets for high (>1500 km) and low (<1500 km) altitude orbits revealed a big difference in a behavior. Satellites were divided on several groups according to the orbital characteristics (altitude and inclination). The relation of satellite anomalies to the environmental parameters was found to be different for various orbits that should be taken into account under developing of the anomaly frequency models.     

Mercury’s Birkeland current system

A consideration is given to the generation of field-aligned currents under different solar wind conditions. The preliminary results from a set of resistive MHD calculations indicate that the field-aligned current system could be significantly changed by the orientation of the interplanetary magnetic field. For most of the cases studied, the total current is less than or on the order of 10⁵ A. Even though this current is at least a factor of 10 smaller than its counter part at Earth, it might still produce some important dynamical effects with interesting consequence on the sporadic behavior of Mercury’s atomic sodium emission.