太阳宇宙线在电离层D层中的电离

本文根据带电粒子对D层大气电离的理论,导出了太阳宇宙线在D层的电子产生率Q(h)的表达式,并计算了不同级别的太阳宇宙线事件、不同能谱参数下,Q(h)在极区随高度的分布。结果表明,不同级别、不同能谱的太阳宇宙线事件在极区产生的电离有显著的差别。同一级别,能谱指数γ越大,在较高的高度上电子产生率越大;能谱指数越小,在较低的高度上电子产生率越大。电子产生率的分布曲线出现明显的双峰,一个峰位于60公里左右,另一个峰位于85公里左右。前一个峰主要由太阳宇宙线中质子产生的,后一个峰主要是z≥2的重粒子成分产生的。本文所得结果明显好于Velinov等人的结果。      

雷暴电场对宇宙线次级粒子中电子的影响

雷暴期间宇宙线次级粒子强度变化与大气电场的关联研究,对分析大气电场加速宇宙线次级带电粒子的机制具有重要意义.采用Monte Carlo方法,模拟研究了雷暴电场对宇宙线次级粒子中电子强度的影响.结果显示,在强度为1000V·cm~(-1)的雷暴电场中,高海拔处电子数目呈指数增长,在大气深度约300g·cm~(-2)处达到极大值,与以往研究提出的相对论电子逃逸雪崩机制相符.模拟结果表明,在地面宇宙线观测实验中,要想得到明显的观测效应,雷暴电场距离探测面的高度应600 m,电场厚度应达到约2000 m.模拟结果为分析雷暴电场与地面宇宙线次级粒子中电子强度的关联性提供了重要参考,为进一步模拟研究雷暴期间高山地面宇宙线强度的变化提供了重要信息.     

电离层D区域电子浓度和电子有效损耗率随时间的变化

本文根据D电离层的电离复合理论,讨论了利用单站、单一频率的LF天波资料连续监测和研究D区域固定高度上电子浓度N(h₀,t)和电子有效损耗率ψ(h₀,t)随时间变化的方法。应用这一方法对武昌站的部分实验资料作了分析,得到了N(h₀,t)的日变化、月变化曲线;并发现ψ(h₀,t)也有明显的日照效应,上、下午呈现显著的不对称性;两者的逐日变化都较小。      

相对论电子束的哨声不稳定性

本文根据相对论粒子与电磁波的共振特性, 讨论了相对论电子束的反常迴旋共振产生的哨声不稳定性.满足共振条件的粒子在动量空间位于一组双曲线上.对于具有损失锥分布的相对论电子束, 相对论效应的共振特性提高了哨声不稳定性的阈值, 对ω～0.5Ω_e频段的哨声影响最大.这种作用在背景参数ω_e～Ω_e时最为显著, 并随ω_e/Ω_e增大而减小.      

雷暴期间次级宇宙线粒子强度瞬时变化研究

雷暴期间大气电场强度变化及其伴随的宇宙线粒子增长的研究, 对于理解大气电场对宇宙线次级粒子的加速机制具有极其重要的意义. 2006年4月至 8月期间, 西藏羊八井宇宙线观测站记录到了20多次雷暴事件. 分析了雷暴期间, ARGO实验scaler模式下次级宇宙线计数与大气电场之间的相关性. 结果显示, 雷暴期间大气电场剧烈变化时, 多重数n=1, 2的次级宇宙线计数率有明显增长, 增幅在1%～9%之间, 然而n=3, n≥ 4的次级宇宙线计数率增长不明显, 甚至没有增长. 该结果为进一步研究雷暴期间大气电场对次级宇宙线的加速机制打下了基础.      

由大气密度的季变化所造成的中、低层大气电离率的季变化

本文对CIRA 1972 模式下的中、低层大气密度季变化所造成的电离率的季变化作了理论计算, 利用宇宙线电离源函数对全球中、低层大气的电离率作了数值计算.计算结果表明, 在70km以下的大气电离率的季变化幅度为百分之几十.在电离峰值高度(约15km)以下幅度为约百分之十, 高度越高变幅越大, 到70km处达35%.在20km以上电离率的季变化趋势与大气密度的季变化趋势大致相同, 夏季比冬季大, 20km以下变化稍为复杂.      

大气中子实时计算模式

为实时评估0~100km高度范围内的大气中子全球分布,对宇宙线在地磁场和大气中的传输过程进行了分析.利用蒙特卡罗方法工具包Geant4,预先计算不同能量的粒子在大气层中产生的次级粒子能谱分布,形成大气次级粒子数据库,并与相关模型进行对比,验证了该数据库的有效性和可靠性.以实测或预报的空间环境参数作为输入,计算同步轨道银河宇宙线和太阳质子事件能谱以及100km高度上的地磁垂直截止刚度,最终得到大气层顶上的粒子能谱.通过对大气次级粒子数据库的线性插值,实现1h分辨率的大气中子能谱和辐射剂量全球分布的实时计算.      

日全食期间中间层大气臭氧光化过程试验

利用包括活O_x、HO_x、和NO_x等成份在内的一维时变光化模式,研究了日全食时上中层大气臭氧和O₂(1△g)的变化特性,并通过与观测资料的比较进行了光化模式的试验.结果表明,日全食时太阳辐照变化对1.27μm气晖影响的高度比曙暮期间明显偏低,利用1.27μm气晖光度计测量大气臭氧的高度范围约为52-67km.1997年3月9日漠河日全食时测量的大气臭氧含量变化幅度为50％.这与考虑O_x、HO_x、和NO_x等成份的光化模式理论模拟结果基本一致.它表明在52-67km高度范围不存在臭氧亏损现象.      

远东地区的微粒E层事件

本文给出了1983-1985年磁暴期间,我国乌鲁木齐等七个站及日本国分寺等五个站出现微粒E层的情况;得到了微粒E层的日变化、月变化和纬度变化;结合同时的地磁、宇宙线、TEC和电离层的变化,对微粒E层出现率作了分析。初步证实:微粒E层的形成和维持与赤道环电流指数(Dst)负变幅大小密切相关,此外还同宇宙线的FD(Forbushdecreases)事件的出现有关。作者认为,沉降粒子可能是低纬地区微粒E层事件的主要粒子来源。      

太阳活动与全球气候变化

太阳不断向地球辐射电磁波和粒子, 太阳辐射是地球气候系统最主要的能量来源. 地球气候系统对太阳活动的响应是一个复杂的过程, 包括辐射过程、动力学过程以及微观物理过程等. 根据太阳辐射的卫星观测结果和重建结果, 例举了古气候、温度、大气环流和云量等方面太阳影响气候的观测证据, 论述了太阳影响气候的三种可能机制, 即太阳总辐射变化可以影响地表温度, 并通过海-气耦合改变大气环流; 太阳紫外辐射通过调制平流层的温度和风场影响下面的对流层; 太阳通过行星际磁场调制银河宇宙线, 而银河宇宙线通过电离大气影响云量, 进而改变地球的能量收支.      

宇宙线强度变化与磁扰K类型

本文把1966—1983年期间发生的679个地磁暴进行了分类,利用统计方法分析了各类磁暴发生前后宇宙线强度的变化特征.突发急始脉冲发生后,宇宙线强度没有出现显著的变化;缓始型暴发生后,宇宙线强度出现Forbush下降,但下降幅度很小;急始型暴发生后,宇宙线强度出现十分明显的Forbush下降.当把急始型暴按K指数大小和持续时间分为5种类型,发现它们伴随的宇宙线Forbush下降是不一样的,其下降幅度随磁暴的增强而加大,下降的速率随磁暴的增强而加快,扰动的持续时间随磁暴的减弱而增加.      

Peculiarities of galactic cosmic ray Forbush effects during October–November 2003

Features of two successive Forbush effects of the galactic cosmic ray intensity in October–November 2003 have been studied based on the neutron monitors data. The rigidity spectrum of the galactic cosmic ray intensity in the course of the first Forbush effect (22–27 October) is gradually hardening, while the rigidity spectrum of the second Forbush effect (28 October–10 November) from the starting moment is very hard. As far, the energy range of the turbulence of the interplanetary magnetic field is in general responsible for the diffusion of galactic cosmic ray particles of the energy 5–50 GeV (to which neutron monitors are sensitive), we postulate that the gradually hardening (from day to day) of the rigidity spectrum of the first Forbush effect is associated with the enhancement of the power spectral density in the energy range of the interplanetary magnetic field turbulence caused by the large scale irregularities generated due to the interaction of the extending high speed disturbances with the background solar wind. The very hard rigidity spectrum (from the starting moment) of the second Forbush effect is generally associated with the well established new structure of the energy range of the interplanetary magnetic field turbulence enriched by the already created large scale irregularities. The gradually softening of the rigidity spectrum during the recovery phase of the second Forbush effect confirms that the disturbed interplanetary magnetic field turbulence step by step returns to the initial state.     

Periodic variations of ionization rate in the low and middle atmosphere

The cosmic ray ionization source functions which were obtained using a simplified extensive air shower model are used to calculate the eleven year cycle, seasonal and diurnal variations of ionization rate in the low and middle atmosphere. The ionization source function, as a function of the penetrating depth and the energy of cosmic ray particles, is the ionization rate per unit depth for a unit flux of incoming cosmic ray particles with certain energy.The calculation of the eleven year cycle variation of ionization rate in the low and middle atmosphere due to the modulation of galactic cosmic ray intensity by solar activity shows that the amplitude is larger at a higher magnetic latitude and is generally larger at higher altitudes. The relative amplitude of fluctuation of the ionization peak value (at altitudes near 15 km) is up to 45% in the magnetic polar region. The ionization rate, due to the seasonal variation of the atmospheric density, varies from several per cent below the ionization peak to several tens per cent above the peak. This seasonal variation of ionization rate reaches 35% at 70 km. The diurnal variation of atmospheric densities caused by atmospheric tidal oscillation can produce a diurnal variation of the ionization rate to an amplitude of several per cent at altitudes above 40 km. The diurnal oscillation is less than 1% below 35 km.     

Observation of enhanced sub-iron (Sc---Cr) to iron ration in low energy cosmic rays of 50–100 MeV/N in spacelab-3

Relative abundances of sub-iron (Sc-Cr) to iron nuclei in low energy (50–100 MeV/N) galactic cosmic rays have been determined from an analysis of about 100 events of heavy ions (Z = 10−28) recorded in a detector assembly flown in the Anuradha cosmic ray experiment in the Spacelab-3 on a six day mission in April–May 1985. The measured abundance ratio of (Sc-Cr)/Fe nuclei in 50–100 MeV/N energy range is 1.1 ± 0.3, and the present result of enhanced ratio of sub-iron to iron nuclei is in agreement with other experimental results in 200–800 MeV/N range. The over-abundance of iron secondaries at these low energies cannot be explained in the conventional models for propagation of cosmic rays. Available experimental data indicate a very different time history for the low energy iron-group, as compared to those of lighter nuclei in galactic cosmic rays.     

1984年4月24日大太阳耀斑爆发对电离层电子总含量的影响

本文给出1984年4月24日2356UT太阳耀斑爆发期间在新乡和重庆两地利用法拉第技术接收日本同步卫星ETS-Ⅱ的甚高频信号所得到的电离层电子总含量的异常变化。两站在耀斑爆发期间的三分半钟内同时观测到电离层电子总含量的突然急剧增加。它们的增量分别为9.4×1016和14.3×1016ele/m2.本文还将偏振仪所观测到的现象与电离层垂测记录及甚低频锁相接收机所观测到的记录作了比较。分析的结果表明,大太阳耀斑期间不仅D层的电子浓度大大增加,而且F层的电子浓度也显着增加,后者是这次总含量剧增的主要部分。      

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.     

Cosmic ray reacceleration on the galactic wind termination shock

Reacceleration of cosmic rays produced by galactic sources on the galactic wind termination shock is considered. The problem of the cosmic ray spectrum continuity is investigated. Numeric results are presented and discussed. We found that a smooth spectral transition from the galactic cosmic rays to the cosmic rays reaccelerated at the galactic wind termination shock is difficult to produce, if the maximum energy of accelerated particles is the same throughout the surface of the termination shock. The possible solution of this problem is the non-spherical termination shock with different maximum energies at different places of the shock.     

The transport of galactic and jovian cosmic ray electrons in the heliosphere

An overview is given on what we know about the cosmic ray diffusion process from the modelling of low-energy (MeV) electron transport in the heliosphere. For energies below ∼300 MeV, these electrons give a direct indication of the average mean free paths because they do not experience large adiabatic energy changes and their modulation is largely unaffected by global gradient and curvature drifts. Apart from galactic cosmic ray electrons, the jovian magnetosphere at ∼5 AU in the ecliptic plane is also a relatively strong source of MeV electrons, with energies up to ∼30 MeV. Therefore, when modelling the transport of these particles in the inner heliosphere, a three-dimensional treatment is essential. By comparing these models to observations from the Ulysses, Pioneer and Voyager missions, important conclusions can be made on e.g., the relative contributions of the galactic and jovian electrons to the total electron intensity, the magnitude of the parallel and perpendicular transport coefficients, and the time dependant treatment thereof.