超高能宇宙线电子在星际介质中的传播

本文研究能量高达1012eV以上宇宙线电子在星际介质中的传播特征, 得到了一些有趣的结果。作为一种自然的猜测, 宇宙线电子高能成份的区域性特征, 可能是导致银河系γ射线辐射的非均匀成团状分布结构的直接原因。      

从海王星到冥王星

"旅行者"2号的发现"旅行者"2号是美国航宇局于1977年8月20日发射的无人星际探测器。它依次拜访了木星、土星和天王星,1989年8月25日到达海王星附近,对被4850千米厚的云层覆盖的海王星进行了考察。"旅行者"2号探测器在飞行期间,不断地将大量星际信息发回到地球,由此扩大了人类对星际的了解。     

空间核动力的现状和发展

众所周知,美苏两国都发射核动力卫星。迄今为止,美国已经发射了十几颗这类卫星,苏联发射的更多,令人瞩目。今后两国仍将继续发射这种卫星。一、核动力装置的优点空间核动力具有许多太阳电池无法相比的优点,它体积小、重量轻、寿命长、可靠性高……。核动力所具有的优点很适合星际探测器使用。比如,美国前几年发射的旅行者卫星,要完成探测木星及土星的基本任务,需要有恒定的电力供应。而土星,木星及更远的星际区域太阳辐射通量低,若用太阳电     

弗兰·巴格纳尔的太空探索前瞻

正40年前,一个轿车大小的设备从佛罗里达州卡纳维拉尔角发射升空。35年后,它成为唯一进入星际空间的人造航天器。一路上,"旅行者"号探测器爆出了飞越木星、土星和土卫六的头条新闻。"旅行者"探测器发射时,弗兰·巴格纳尔还是一个学生。那时,她就探测器围绕木星收集的数据写下了博士论文。现在,作为科罗拉多大学波尔得分校天体物理学和行星科学教授,以及美国航空航天局外行     

两个临近脉冲型太阳能量电子事件的观测与拟合

WIND飞船在2010年11月15日观测到两个临近的脉冲型太阳能量电子事件, 这两个事件在1AU处呈现出不同类型的通量-时间曲线. 事件一的通量表现出快速上升及快速下降的特性; 事件二则表现为缓慢上升, 更缓慢下降, 事件二的持续时间是事件一的5～17倍. 以往的解释认为事 件二中的电子在行星际受到了更强的散射. 本文引入等腰三角形的释放函数并 求解电报方程, 利用得到的解对1AU处的观测进行拟合. 根据最佳拟合结果 反推两事件在太阳上的释放函数和在行星际传播的平均自由程, 发现造成两事 件在1AU处能谱和通量-时间曲线形状不同的原因是太阳上电子 加速过程的不同而非行星际散射. 结合SOHO卫星的白光观测, 发现两事件可能 与一个CME (日冕物质抛射)相关, 并进一步推测了这两个太阳电子事件可能 的加速图像.      

令人期待的矮行星之旅

<正>进入2015年,在星际探测迷的眼中,彗星已经逐渐从人们的视线中淡出,矮行星却冉冉升起。3月,美国航宇局的"黎明"号探测器将到达谷神星。谷神星是火星和木星之间最大的一颗矮行星。人们认为谷神星表层之下蕴藏着水冰。此外,在航行了50亿千米后,9年多前发射的美国     

美“旅行者”将进入银河系寻找文明人类

[英国《空间飞行》杂志1978年4月报道] 美航宇局去年八、九月分别发射的两个旅行者宇宙探测器,现在正借助引力探索外行星。当它们逃脱太阳系时,将以每秒17.2公里的速度飞向广阔无垠的星际空间。旅行者-1将于明年3月到达木星,1980年11月飞过土星及其光环。旅行者-2明年7月飞经木星,1981年8月经过土星,可能在1986年6月飞临天王星。当这两个宇宙飞行器1989年穿过冥王     

月表磁异常影响的太阳风电子反射运动

模拟太阳风电子向月表运动的轨迹, 研究由于月表磁异常的存在造成的电子反射运动. 首先设定行星际磁场Bsw 指向月球并与月表垂直, 将月表的磁异常区看成是一个磁偶极子, 偶极矩大小为Mcb; 然后分别考察该偶极矩与行星际磁场方向平行, 反平行以及±90° 的情形, 通过计算发现, 被反射的电子数目会随着磁偶极矩和行星际磁场的方向改变而改变. 在偶极矩与行星际磁场平行的情况下, 反射率最大; 随着夹角的增大, 反射率减小. 这些结果为利用电子反射法高精度遥测月表磁场提供了很重要的信息.      

太阳风中动力论Alfven波湍流谱(b)二次激发

根据行星际Alfven湍流是由动力论Alfven波集合形成的模型理论。将行星际Alfven湍流分为三个区域:湍流耗散区、二次激发区和湍流惯性区。并对各区湍流谱的特性分别给出解释。由动力论Alfven波的二次激发和衰减,解释了太阳风高速流质子温度高于电子的事实。      

磁层扰动对同步高度太阳质子截止刚度的影响

采用Williams—Mead磁场模式,考虑当行星际磁场存在南向分量时的磁层扰动情况,计算了一组同步卫星所在位置太阳质子截止刚度随地方时的变化。计算结果表明,当考虑行星际磁场存在5γ南向分量时,截止刚度值显著降低。午夜西方截止刚度极小值由原来的3.1兆电子伏降至1.9兆电子伏,中午西方截止刚度极大值由原来的22.1兆电子伏降至16.6兆电子伏。与同步高度太阳质子的观测结果更加接近。     

Modelling and observing Jovian electron propagation times in the inner heliosphere

The propagation of Jovian electrons in interplanetary space was modelled by solving the relevant transport equation numerically through the use of stochastic differential equations. This approach allows us to calculate, for the first time, the propagation time of Jovian electrons from the Jovian magnetosphere to Earth. Using observed quiet-time increases of electron intensities at Earth, we also derive values for this quantity. Comparing the modelled and observed propagation times we can gauge the magnitude of the transport parameters sufficiently to place a limit on the 6 MeV Jovian electron flux reaching Earth. We also investigate how the modelled propagation time, and corresponding Jovian electron flux, varies with the well-known ∼13 month periodicity in the magnetic connectivity of Earth and Jupiter. The results show that the Jovian electron intensity varies by a factor of ∼10 during this cycle of magnetic connectivity.     

太阳高能电子束通过空间振荡轴向场产生的电磁不稳定性

本文基于太阳高能电子和日冕区开放场及行星际磁场特征，建立了相对论电子束与伴有空间变化（空间周期变化）的轴向场相互作用模型，用数值方法研究了该体系产生的电磁不稳定性，结果指出只有当太阳高能电子束速度和空间振荡场波数大到一定程度时，该体系才可激发在旋电磁模不稳定性，当太阳高能电子束逐一通过日冕和行星际空间时，激发具有波频向低频漂移特征的电磁波．     

行星际磁场的螺旋扇形过渡区

从行星际磁场的大尺度螺旋形构型和扇形边界附近太阳风流动与冕旒的可能相关,本文得到一个推论,即在行星际空间可能存在一种较厚的螺旋扇形过渡区。行星际磁场和太阳风的实地观测证实了这种较厚的螺旋扇形过渡区的存在。在所分析的45个螺旋扇形过渡区中,磁场强度都不为零;大部分大于或小于周围平均场强。本文进一步分析了磁增大和磁减小两类过渡区中的物理性质和可能成因。      

行星际高密度结构的磁场位形

本文统计分析了第20太阳周行星际高密度结构的磁场位形。结果说明当出现高密度结构时行星际磁场相对于黄道面的倾角约增大10°。这种增大并非流相互作用或电流片倾斜和折皱所引起的,而可能是非恒稳太阳风流所具有的磁场位形。当出现高速流或扇形边界时,由于高密度结构后平行于Parker螺旋线的分量增大,磁场在黄逋面内对螺旋线的偏离角减小。      

Observations of solar radio bursts from meter to kilometer wavelengths

Using the Clark Lake Radioheliograph data we present direct evidence that type III electron streams propagate in dense coronal streamers. We also present imaging observations of meter-decameter microbursts, which appear to be similar to those observed in hard X-rays. At meter-decameter wavelengths, these microbursts appear to be due to plasma radiation. From observations made with ISSE-3, we discuss the characteristics of hectometer and kilometer wavelength radio bursts. In particular, we show that from studies of type III storms that the exciter electrons propagate along spiral structures, where the density is enhanced and that there is an acceleration of the solar wind. We discuss type II bursts at kilometer wavelengths, compare them with meter type II bursts and discuss their association with interplanetary shocks. We show that the interaction between type III electron streams and shocks at kilometer wavelengths can provide information on the interplanetary shock geometry. Finally, we discuss the possibility that some shock associated (SA) events may be emissions caused by electrons accelerated lower in the atmosphere rather than high in the corona in type II shocks.Recent advances in solar research have resulted from new work on plasma radiation theory, new observations of active regions and flares across the electromagnetic spectrum and the availability of spacecraft in situ measurements of solar ejecta. In this paper, we review some results obtained with the Clark Lake multifrequency radioheliograph at meter-decameter wavelengths and from satellite multifrequency directive observations at hectometer and kilometer wavelengths. We present evidence that type III electrons propagate in dense coronal streamers, and that frequently observed microbursts (presumably of type III) at meter-decameter wavelengths are due to plasma radiation. We discuss observations of hectometer and kilometer type III radio storms which reveal information about active region structures, interplanetary magnetic field configuration, and solar wind acceleration. We also discuss kilometer type II bursts, interactions between type III electrons and interplanetary shocks, and present some new results on shock associated (SA) events.     

Radiation analysis for manned missions to the Jupiter system.

An analysis for manned missions targeted to the Jovian system has been performed in the framework of the NASA RASC (Revolutionary Aerospace Systems Concepts) program on Human Exploration beyond Mars. The missions were targeted to the Jupiter satellite Callisto. The mission analysis has been divided into three main phases, namely the interplanetary cruise, the Jupiter orbital insertion, and the surface landing and exploration phases. The interplanetary phase is based on departure from the Earth-Moon L1 point. Interplanetary trajectories based on the use of different propulsion systems have been considered, with resulting overall cruise phase duration varying between two and five years. The Jupiter-approach and the orbital insertion trajectories are considered in detail, with the spacecraft crossing the Jupiter radiation belts and staying around the landing target. In the surface exploration phase the stay on the Callisto surface is considered. The satellite surface composition has been modeled based on the most recent results from the GALILEO spacecraft. In the transport computations the surface backscattering has been duly taken into account. Particle transport has been performed with the HZETRN heavy ion code for hadrons and with an in-house developed transport code for electrons and bremsstrahlung photons. The obtained doses have been compared to dose exposure limits.     

PAMELA observational capabilities of Jovian electrons

PAMELA is a satellite-borne experiment that has been launched on June 15th, 2006. It is designed to make long duration measurements of cosmic radiation over an extended energy range. Specifically, PAMELA is able to measure the cosmic ray antiproton and positron spectra over the largest energy range ever achieved and will search for antinuclei with unprecedented sensitivity. Furthermore, it will measure the light nuclear component of cosmic rays and investigate phenomena connected with solar and earth physics. The apparatus consists of: a time of flight system, a magnetic spectrometer, an electromagnetic imaging calorimeter, a shower tail catcher scintillator, a neutron detector and an anticoincidence system. In this work a study of the PAMELA capabilities to detect electrons is presented. The Jovian magnetosphere is a powerful accelerator of electrons up to several tens of MeV as observed at first by Pioneer 10 spacecraft (1973). The propagation of Jovian electrons to Earth is affected by modulation due to Corotating Interaction Regions (CIR). Their flux at Earth is, moreover, modulated because every 13 months Earth and Jupiter are aligned along the average direction of the Parker spiral of the Interplanetary Magnetic Field.PAMELA will be able to measure the high energy tail of the Jovian electrons in the energy range from 50 up to 130 MeV. Moreover, it will be possible to extract the Jovian component reaccelerated at the solar wind termination shock (above 130 MeV up to 2 GeV) from the galactic flux.     

Cosmic-ray diffusion in the inner heliosphere

For about the last 40 years, we have been trying to understand the propagation of cosmic rays and other energetic charged particles through the interplanetary medium. Identification of the basic processes affecting the propagation, namely diffusion, convection by the solar wind, adiabatic deceleration, and gradient and curvature drifts, was attained early on, but reaching detailed physical understanding, particularly of the roles of diffusion and gradient and curvature drifts, continues as an active topic of research to this day. Particularly unclear is the nature of the cross-field propagation. Many observations seem to require more efficient cross-field propagation than theoretical propagation models can easily produce. At the same time, there are other observations that seem to show strong guidance of the particles by the interplanetary magnetic field. With current measurements from spacecraft near Earth and from the Ulysses spacecraft, which samples nearly the complete range of heliographic latitudes in the inner heliosphere, critical tests of the ways in which cosmic rays and other energetic charged particles propagate through the interplanetary medium are possible. I briefly review the status of observations that are relevant to the characterization of diffusive propagation in the inner heliosphere and will present evidence for a possibly previously overlooked contribution from transport along magnetic flux tubes that deviate dramatically from the average interplanetary spiral configuration.     

The local time dependence of the anisotropic solar cosmic ray flux.

The distribution of the solar cosmic radiation flux over the earth is not uniform, but the result of complex phenomena involving the interplanetary magnetic field, the geomagnetic field and latitude and longitude of locations on the earth. The latitude effect relates to the geomagnetic shield; the longitude effect relates to local time. For anisotropic solar cosmic ray events the maximum particle flux is always along the interplanetary magnetic field direction, sometimes called the Archimedean spiral path from the sun to the earth. During anisotropic solar cosmic ray event, the locations on the earth viewing "sunward" into the interplanetary magnetic field direction will observe the largest flux (when adjustments are made for the magnetic latitude effect). To relate this phenomena to aircraft routes, for anisotropic solar cosmic ray events that occur during "normal quiescent" conditions, the maximum solar cosmic ray flux (and corresponding solar particle radiation dose) will be observed in the dawn quadrant, ideally at about 06 hours local time.     

Temporal profiles of solar energetic particle events from SOHO/EPHIN data

Temporal profiles of energetic ions and electrons observed at 1 AU during solar energetic particle events are mainly determined by particle injection features, the observer location relative to the source region at the Sun, and the interplanetary space plasma and field conditions during particle transport. In this work, temporal profiles of 18 solar energetic particle events have been analyzed by fitting a pulse function to them in order to find a set of parameters which can be used to characterize the events.