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.     

The beginning of cosmic ray astrophysics

A short history of the beginning of cosmic ray (CR) astrophysics is considered: from the hypothesis on CR origin as a result of Supernova explosions in the Metagalaxy, to a model of solar origin of CR, galactic origin based on the stochastic mechanism of charged particle acceleration in interstellar space, to extragalactic and hierarchical models of CR origin, as well as galactic CR origin taking into account radio-astronomical data. We consider also the first balloon results on the chemical contents of primary CR (especially of the contents Li, Be, B), important for any model of CR origin. Investigations of the injection problem, CR drift and diffusion acceleration by shock waves, and CR generation in Supernova remnants were also important steps in the beginning of CR astrophysics.     

Model for induced ionization by galactic cosmic rays in the Earth atmosphere and ionosphere

The ionization profiles produced by galactic cosmic rays in the Earth atmosphere and ionosphere are obtained on the basis of Monte Carlo simulations. Cascade processes in the atmosphere are simulated using CORSIKA 6.52 code with FLUKA 2006 and QGSJET II hadronic interaction subroutines. Proton induced showers are considered using a realistic atmospheric model (US Standard Atmosphere). The energy deposit from different components is taken into account, namely electromagnetic, hadron and muon components. The curvature of the atmosphere is considered in the computer code. On the basis of the computed ionization yield function the ion pair production rate in the atmosphere is obtained for different conditions and locations. The model is applicable to the entire atmosphere, from ground level to upper atmosphere. Several applications of the obtained results are discussed. The Monte Carlo simulation model considers nuclear interactions below the altitude of 35 km. It is compared with analytical–numerical electron production rate model. The latter model which takes into account the electromagnetic interactions above altitudes of 35 km has two main regions of application: above 50 km (thin target model) and between 35 and 50 km (intermediate target model). A good agreement between the CORSIKA results and analytical–numerical model results is found above altitude of 35 km.     

Active shielding for long duration interplanetary manned missions

For long duration interplanetary manned missions the protection of astronauts from cosmic radiation is an unavoidable problem that has been considered by many space agencies. In Europe, during 2002–2004, the European Space Agency supported two research programs on this thematic: one was the constitution of a dedicated study group (on the thematic ‘Shielding from cosmic radiation for interplanetary missions: active and passive methods’) in the framework of the ‘life and physical sciences’ report, and the other an industrial study concerning the ‘radiation exposure and mission strategies for interplanetary manned missions to Moon and Mars’. Both programs concluded that, outside the protection of the magnetosphere and in the presence of the most intense and energetic solar events, the protection cannot rely solely on the mechanical structures of the spacecraft, but a temporary shelter must be provided. Because of the limited mass budget, the shelter should be based on the use of superconducting magnetic systems. For long duration missions the astronauts must be protected from the much more energetic galactic cosmic rays during the whole mission period. This requires the protection of a large habitat where they could live and work, and not the temporary protection of a small volume shelter. With passive absorbers unable to play any significant role, the use of active shielding is mandatory. The possibilities offered by superconducting magnets are discussed, and recommendations are made about the needed R&D. The technical developments that have occurred in the meanwhile and the evolving panorama of possible near future interplanetary missions, require revising the pioneering studies of the last decades and the adoption of a strategy that considers long lasting human permanence in ‘deep’ space, moreover not only for a relatively small number of dedicated astronauts but also for citizens conducting there ‘normal’ activities.     

Lunar cosmic ray radiation environments during Luna and Lunar Reconnaissance Orbiter missions

The RV-2N-series instruments onboard Luna missions and the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) instrument onboard Lunar Reconnaissance Orbiter (LRO) were designed to characterize the global lunar radiation environment and its biological impacts by measuring cosmic ray (CR) intensity. In this study, we have shown that the RV-2N-series instruments onboard of Russian Luna missions and the CRaTER reliably detect both background CRs and solar proton events (SPEs) in the lunar radiation environment using the proton intensity measured by the RV-2N-series onboard Luna missions out of the Russian Luna program for the exploration of the Moon (November 1970–August 1975) and the CR intensity on the Moon observed by the CRaTER (June 2009–March 2011). Those were compared with the CR intensities observed by neutron monitors (McMurdo, Thule, Oulu) on the Earth. The sunspot number is used as the index of solar activity (NOAA National Geophysical Data Center). As a result, the background CR intensities on the Moon turned out to have a good anti-correlation with the solar activity. We have also identified the proton intensity increasing events on the Moon which have the similar profiles to those observed by neutron monitors on the Earth. Most of these events show the significant increase of proton intensities in the lunar radiation environment when the SPEs associated with solar eruptions are verified. Therefore, most of the proton intensity increasing events are associated with the energetic solar particles in the lunar environment.     

X射线脉冲星脉冲到达航天器时间测量

X射线脉冲星脉冲到达时间(TOA)的空间测量是航天器自主导航和用脉冲星钟作航天器时间标准的基础.在简要介绍地面射电观测TOA测量方法基础上,重点研究了X射线脉冲星脉冲到达时间的空间测量方法和算法.讨论了利用X射线脉冲星辐射光子到达时间观测,建立X射线脉冲轮廓的方法;给出了通过观测得到的X射线脉冲轮廓与标准脉冲轮廓比较,精确确定TOA的测量方法和实用算法.讨论了削弱多普勒效应对TOA测量影响的方法.      

On the effects of dynamical turbulence on the perpendicular diffusion of low-energy cosmic ray electrons

Diffusion perpendicular to the heliospheric magnetic field plays an integral role in the transport of charged particles in the heliosphere. In this study the perpendicular diffusion coefficient of low-energy cosmic ray electrons is calculated, using an equation derived from the random ballistic decorrelation interpretation of nonlinear guiding centre theory. An observationally motivated 2D turbulence power spectrum is assumed and the effects of various turbulence inputs on the resulting perpendicular diffusion coefficient are investigated. The perpendicular diffusion coefficients are first determined at 1 AU, for both magnetostatic and dynamical turbulence conditions. These solutions are also evaluated for radial distances of 0.1 AU to 10 AU to further investigate the values of the perpendicular diffusion coefficients in the very inner heliosphere. The results of this study show that the dissipation range of the turbulence power spectrum provides a negligible contribution towards the perpendicular diffusion coefficient, and that solutions derived using only the energy containing range serve as good approximations for solutions derived assuming the full 2D turbulence power spectrum. Finally, it is shown that the effects of dynamical turbulence, as considered in the present study, do not affect the perpendicular diffusion coefficients derived from the scattering theory considered here.     

预追踪法在搭建RCS计算平台中的应用

 介绍综合不同RCS贡献机理的计算平台的搭建方法。针对射线追踪法的计算量是这类RCS计算平台计算效率的瓶颈这一现状,提出仅对多次散射区采用射线追踪计算来减小计算量的方法。给出一种通过粗略的射线追踪来确定多次散射区的方法,并用该方法获得任意目标的散射分布图。对预追踪法在RCS平台的搭建中的应用方式进行探讨,并预测效果。通过具体的计算实例验证预追踪法的效果,并给出几类典型目标的多次散射区比例系数,可供采用预追踪法时参考。计算结果表明,在不改变计算精度的条件下,预追踪法可以将RCS计算平台中射线追踪部分的计算量减少到原来的1/3以下。对散射分布的可能应用做出展望,可以作为后续工作的指导。     

Relation between different theories for cosmic ray cross field diffusion

In the past few year several theories have been presented for describing cosmic ray scattering across the mean magnetic field. It is the purpose of the present article to discuss the relation between these different theories in order to improve our understanding of cosmic ray perpendicular scattering and to explore the parameter regimes for which these different theories are valid.     

Effect of “Noisy” sun conditions on aircrew radiation exposure

In computer codes used to estimate the aircrew radiation exposure from galactic cosmic radiation, a quiet sun model is usually assumed. A revised computer code (PCAIRE ver. 8.0f) is used to calculate the impact of noisy sun conditions on aircrew radiation exposure. The revised code incorporates the effect of solar storm activity, which can perturb the geomagnetic field lines, altering cutoff rigidities and hence the shielding capability of the Earth’s magnetic field. The effect of typical solar storm conditions on aircrew radiation exposure is shown to be minimal justifying the usual assumptions.