“风云一号”气象卫星

本文叙述了中国第一颗气象卫星“风云一号”。这是一颗试验气象卫星,重750公斤,其主体为1.40米×1.40米×1.20米的六面体,连同太阳电池阵共展宽8.60米,高1.76米。运行在太阳同步轨道,高度900公里,倾角99°,每天绕地球运行14圈。地面接收到高质量的图象资料和轨道空间的辐射环境资料。     

Transient Effects and Disturbed Conditions

In the present phase of the solar cycle no big transients leading to strong modulation had been observed after 1991. Apart from a few minor disturbances cosmic rays were still recovering to a new intensity maximum. It was suggested, therefore, that existing literature from previous cycles should be critically reviewed. The scene was set by the introductory papers on— phenomenology of cosmic ray modulation in successive solar cycles throughout the heliosphere— the present state of models for long term modulation and their shortcomings— the relation between cosmic ray variations and the magnitude of the interplanetary magnetic field (the CR-B-relation)— charge dependent effects.In the discussions, the study of propagating diffusive disturbances and the CR-B-relation played a central role. The difference was stressed between isolated transient disturbances in the inner solar system (Forbush decreases), and the long lasting, step-like decreases caused by merged interaction regions in the outer heliosphere. The recovery rates following the step-like decreases vary with the phase in the 22-year solar cycle. In some cases this requires a modification of existing drift models. In the outer heliosphere, the CR-B-relation leads to the result 1/ between the diffusion coefficient and the field magnitude . This simple result is a challenge for theoreticians to derive the perpendicular diffusion coefficient fromfirst principles. The three articles in this report essentially follow the list of open points and arguments just presented.The article "Observations and Simple Models" is organised around the model of a propagating diffusive barrier, its application to Forbush effects in the inner heliosphere and to decreases caused by merged interaction regions in the outer heliosphere. Acomparison of observed Forbush decreases with model predictions requires a careful separation of the two steps related to the turbulent region behind the shock front and the closed magnetic field regions of the ejecta (the interplanetary counterparts of coronal mass ejections). It is shown that models for propagating disturbances can be used to derive values of the diffusion coefficients phenomenologically, not only during the disturbance, but also in the ambient medium.The "Modeling of Merged Interaction Regions" summarizes the dynamic and time-dependent process of cosmic ray modulation in the heliosphere. Numerical models with only a time-dependent neutral sheet prove to be successful when moderate to low solar activity occurs but fail to describe large and discrete steps in modulated cosmic rays when solar activity is high. To explain this feature of heliospheric modulation, the concept of global merged interaction regions is required. The com-bination of gradient, curvature and neutral sheet drifts with these global merged interaction regions has so far been the most successful approach in explaining the 11-year and 22-year cycles in the long-term modulation of cosmic rays.The "Remarks on the Diffusion Tensor in the Heliosphere" describe available theories of perpen-dicular diffusion and drift, and discuss their relevance to cosmic rays in the heliosphere. In addition, the information about diffusion coefficients and spatial gradients obtained from the analysis of steady state anisotropies at neutron monitor energies is summarized. These topics are intimately related to the other two articles. They are also part of the general discussion about the "Diffusion Tensor throughout the Heliosphere" which played an important role in all working groups.     

低平流层温度对银河系宇宙线强度变化的响应

选用芬兰中子堆监测站从lop年7月至1989年3月的宇宙线强度月平均曲线数据,和在相对应期间我国境内海拉尔等4个高空气象观测站的30hPa和100hPa等位势高度上常规气温观测月平均资料,经统计分析,取得初步结果:低平流层气温与银河系宇宙线辐射强度之间呈现负相关的特性;与银河系宇宙线辐射强度峰区和谷区相对应会在低平流层中引起幅值为2-3℃的温度变化;不同纬度观测站所得观测数据表明,上述增温幅值随纬度降低而减少。      

中山站电离层尖峰脉冲型吸收统计特性

通过对南极中山站成像式宇宙噪声接收机2000至2001年的观测数据进行分析,得到了189例电离层尖峰脉冲型吸收事件,按其发生时间可分为夜侧吸收事件(69例)和日侧吸收事件(120例).对这两类吸收事件进行对比统计研究,得到了其吸收发生时间、吸收持续时间、吸收强度、吸收区域形状和空间尺度、运动状况以及吸收事件与地磁Kp指数关系等特性,并对电离层尖峰脉冲型吸收的可能产生机制进行了讨论.      

The scaler mode in the Pierre Auger Observatory to study heliospheric modulation of cosmic rays

The impact of the solar activity on the heliosphere has a strong influence on the modulation of the flux of low energy galactic cosmic rays arriving at Earth. Different instruments, such as neutron monitors or muon detectors, have been recording the variability of the cosmic ray flux at ground level for several decades. Although the Pierre Auger Observatory was designed to observe cosmic rays at the highest energies, it also records the count rates of low energy secondary particles (the scaler mode) for the self-calibration of its surface detector array. From observations using the scaler mode at the Pierre Auger Observatory, modulation of galactic cosmic rays due to solar transient activity has been observed (e.g., Forbush decreases). Due to the high total count rate coming from the combined area of its detectors, the Pierre Auger Observatory (its detectors have a total area greater than 16,000 m²) detects a flux of secondary particles of the order of ∼10⁸ counts per minute. Time variations of the cosmic ray flux related to the activity of the heliosphere can be determined with high accuracy. In this paper we briefly describe the scaler mode and analyze a Forbush decrease together with the interplanetary coronal mass ejection that originated it. The Auger scaler data are now publicly available.     

Radial distribution of galactic cosmic rays at solar maximum

In this paper we analyze the spatial distribution of galactic cosmic rays during periods of maximum solar activity of the cycles 21, 22 and 23. We have used a two dimensional model to solve the cosmic ray transport equation. This model includes all relevant physical processes: diffusion, convection, drift and shock effects on cosmic ray propagation inside the heliosphere. We focused on the study of the radial distribution of galactic cosmic rays, and compare our results with the spacecraft observations for two energies (175 MeV H and 265 MeV/n He). Although the radial intensities of galactic cosmic rays can be explained qualitatively with all three local interstellar spectra (LISs) used in this work, we applied a reduced chi-squared analysis to investigate the best LIS that could fit the data.     

Response of the Earth’s lower ionosphere to the Ground Level Enhancement event of December 13, 2006

In this study we analyze the Ground Level Enhancement Event No 70 observed on December 13, 2006, by correlating the observations from two research topics: Cosmic rays and Very Low Frequency (VLF < 30 kHz) wave propagation, as two ground based techniques for the detection of solar proton events, and their impact on the lower ionosphere. The observations have been endorsed from recordings of worldwide network ground based Neutron Monitors as well as by satellite data from the satellites GOES 12 (www.swpc.noaa.gov) and Pamela (www.pamela.roma2infn.it).     

Origin and Evolution of the Light Nuclides

After a short historical (and highly subjective) introduction to the field, I discuss our current understanding of the origin and evolution of the light nuclides D, ³He, ⁴He, ⁶Li, ⁷Li, ⁹Be, ¹⁰B and ¹¹B. Despite considerable observational and theoretical progress, important uncertainties still persist for each and every one of those nuclides. The present-day abundance of D in the local interstellar medium is currently uncertain, making it difficult to infer the recent chemical evolution of the solar neighborhood. To account for the observed quasi-constancy of ³He abundance from the Big Bang to our days, the stellar production of that nuclide must be negligible; however, the scarce observations of its abundance in planetary nebulae seem to contradict this idea. The observed Be and B evolution as primaries suggests that the source composition of cosmic rays has remained ∼constant since the early days of the Galaxy, a suggestion with far reaching implications for the origin of cosmic rays; however, the main idea proposed to account for that constancy, namely that superbubbles are at the source of cosmic rays, encounters some serious difficulties. The best explanation for the mismatch between primordial Li and the observed “Spite-plateau” in halo stars appears to be depletion of Li in stellar envelopes, by some yet poorly understood mechanism. But this explanation impacts on the level of the recently discovered early “⁶Li plateau”, which (if confirmed), seriously challenges current ideas of cosmic ray nucleosynthesis.     

The Composition of Cosmic Rays and the Mixing of the Interstellar Medium

The differences between the composition of Galactic cosmic rays and that of the interstellar medium are manifold, and they contain a wealth of information about the varying processes that created them. These differences reveal much about the initial mixing of freshly synthesized matter, the chemistry and differentiation of the interstellar medium, and the mechanisms and environment of ion injection and acceleration. Here we briefly explore these processes and show how they combine to create the peculiar, but potentially universal, composition of the cosmic rays and how measurements of the composition can provide a unique measure of the mixing ratio of the fresh supernova ejecta and the old interstellar medium in this initial phase of interstellar mixing. In particular, we show that the major abundance differences between the cosmic rays and the average interstellar medium can all result from cosmic ray ion injection by sputtering and scattering from fast refractory oxide grains in a mix of fresh supernova ejecta and old interstellar material. Since the bulk of the Galactic supernovae occur in the cores of superbubbles, the bulk of the cosmic rays are accelerated there out of such a mix. We show that the major abundance differences all imply a mixing ratio of the total masses of fresh supernova ejecta and old interstellar material in such cores is roughly 1 to 4. That means that the metallicity of ∼3 times solar, since the ejecta has a metallicity of ∼8 times that of the present interstellar medium.     

Fluxes and nuclear abundances of cosmic rays inside the magnetosphere using a transmission function approach

At 1 AU and outside the Earth’s magnetosphere, the relative abundances to protons for He (He/p), C (C/p) and Fe (Fe/p) nuclei were calculated using the observation data of AMS-01 (for p and He) and HEAO-3 (for C and Fe) above 0.8 GeV/nucleon. In addition, the transmission function (TF) for the GCR propagation inside the magnetosphere was evaluated using the IGRF and T96 (introduced by Tsyganenko and Stern) models to obtain permitted and forbidden trajectories inside the magnetosphere. The TF allowed one to derive the primary He-nuclei fluxes in the same geomagnetic regions of AMS-01 observations. These fluxes were found in good agreement with the observation data. Furthermore inside the magnetosphere in addition to the flux of helium, it allowed one to obtain those of the primary p, C, and Fe nuclei and the relative abundances of He, C and Fe nuclei to protons from the same observation data of AMS-01 and HEAO-3 above ≈0.8 GeV/nucleon. Up to a geomagnetic latitude of ≈45.84°, the relative isotopic abundances were found to depend on the mass number I_isot and, on average, range from a factor ≈2.31 up to ≈3.35 larger than those outside the magnetosphere at 1 AU. Thus, the magnetospheric isotopic/nuclear relative abundances differ from those inside the solar cavity and those in the interstellar space. The usage of the TF approach can allow one to determine the nuclear abundances in the magnetosphere at any geomagnetic latitude and, thus, any orbit, provided that the CR spectra are determined at 1 AU.