弯曲磁场中相对论性电子辐射的自吸收性质及等离子体影响

根据同步曲率辐射理论，论文推导了真空中和等离子体中弯曲磁场下相对论性电子辐射的自吸收系数，发现真空中同步曲率辐射与同步辐射一样没有负吸收放大作用，而等离子体对辐射谱和自吸收性质有重大影响，存在脉泽放大效应。这些结果有可能对宇宙中多种射电源的射电高亮温度等问题提供可能的解释。     

一种对伽玛暴瞬时谱的新解释

研究了幂律分布电子的同步曲率辐射在伽玛暴（gamma-ray burst,GRB）的物理条件下的表现,并用同步曲率辐射机制代替同步辐射来解释伽玛暴的瞬时谱,尤其是那些出现拐点和高能过剩的谱,还拟合了几个实际的有拐点和高能过剩的伽玛射线暴的瞬时谱.从中可以看出,同步曲率辐射机制对整个瞬时谱能够做出统一和合理的解释.在对高能过剩部分的解释中,同步曲率辐射机制不需再人为引入任何其他机制,因此可调参数少.此外,该机制还能对发射区磁场给出更加详细的描述,尤其是对磁场的曲率半径有了严格的约束,因此对磁场的形成机制给出严格的限制,支持了磁场产生于激波的理论模型.将来对更高能部分的更精细的观测将能够对我们的模型进行进一步检验.最后用同步曲率辐射对GRB 941017的谱的瞬时谱部分的演化进行了拟合和讨论.     

相对论电子在螺旋磁场中的辐射

从运动荷电粒子产生的流出发 ,导出相对论电子和相对论电子集在等离子体及真空情况下曲率辐射的能量谱及辐射总能量 ,分析了等离子体对辐射的影响 .并着重用曲率辐射公式讨论了在磁流体吸积盘的特殊螺旋强磁场中的辐射特点 .     

γ射线暴火球模型的光学余辉辐射

按照γ射线暴火球模型的动力学演化规律,利用相对论电子在磁场中作同步加速辐射时谱分布的特点,用求峰值频率辐射的方法,计算了γ射线暴红光波段余辉辐射流量随时间的变化与γ射线暴GRB970228的观测结果比较,符合甚好,说明同步加速辐射是γ射线暴余辉主要的辐射机制,也进一步证明了火球模型的正确。     

光学厚的介质中同步辐射谱

文章利用等离子体中湍动波谱计算公式得到,在光学厚的介质中麦克斯韦分布的极端相对论电子在磁场中产生的同步加速辐射谱为瑞利-金斯谱。代入太阳活动区物理量的特征值,经过计算分析发现该谱对太阳耀斑过程中少数快电子的加速是有效的,而对基础等离子体的加热的贡献很小。     

中子星倾斜转子模型Gamma射线辐射角分布特性

将中子星近似看做带有偶极磁场的倾斜转子,本文从经典辐射理论出发,用计算机数值计算方法计算了从星近极区表面飞出的原电子的γ射线辐射角分布。结果表明,影响辐射角分布特性的主要因素是磁力线曲率和电子能量耗散。偶极磁场的强烈畸变将在一定程度上导致辐射的方向弥散.     

利用同步偏振辐射统计测量磁化强度

星际磁场在天体物理中具有重要作用，但测量其强度是极其困难的。本文基于同步偏振辐射理论开发了测量磁化强度的新技术，建立了同步偏振辐射强度的标准差和平均值的比值与阿尔文马赫数的幂律关系。此外，该技术也应用于Planck观测数据，实现了磁化强度的测量。     

毫秒脉冲星的高能辐射

 根据自恰毫秒脉冲星磁层外隙模型讨论毫秒脉冲星的高能辐射机制.其中X射线由2个热成分和1个幂律成分组成,γ射线由外隙粒子同步-曲率辐射产生.在此基础上,理论计算了11颗X射线波段及其他39颗在射电波段观测到的毫秒脉冲星,所得理论与观测符合较好,表明该模型能较好地解释毫秒脉冲星的高能辐射机制.     

Blazars多波段辐射机制研究

基于均匀同步自康普顿模型,用双幂率电子谱分布对Fermi-LAT观测到的有高能辐射的TeV Blazar源Mark 421、3C 273、PKS 2155-304的辐射能谱进行计算,并考虑了河外背景光(EBL)的吸收,对谱形做了修正。计算结果与TeV Blazar源Mark 421、3C 273、PKS 2155-304宁静状态下的多波段准同时性观测结果符合得很好,由此得到TeV Blazar源宁静状态下喷流磁场、多普勒因子,电子数密度等几何参数和物理参数。     

相对论性电子在弯曲磁场中的辐射

计算了等离子体介质中,沿弯曲螺旋线运动的相对论电子的辐射谱,进一步导出了真空中的能量辐射公式．     

外磁场中Hubbard系统的表面传导电子能和自旋波

讨论了在外磁场中Hubbard系统的表面传导电子能和自旋波,发现在外磁场中Hubbard系统表面传导电子能明显不同于系统内部传导电子能,这正好可以解释在固体表面其特性是有异常的.对于自旋波谱的研究发现,由于外磁场的介入,自旋波谱不仅与自旋向上和向下的电子数有关,而且由于外磁场的存在而变得较为复杂.     

非理想注入电子在平面型波荡器中的运动与辐射

对于平面型波荡器取一维近似,忽略光场对于电子运动的影响,给出了非理想注入相对论性电子在平面型波荡器中的运动方程,进而基于电磁辐射的一般理论基于Lénard-Wicherd势,导出了相应的电磁辐射的角度、频谱分布的表达式.     

KSTAR装置逃逸电子同步辐射功率谱的研究

电子逃逸是托卡马克等离子体中一种普遍的现象.对逃逸电子的监测是保护装置第一壁材料的基础.托卡马克上等离子体芯部逃逸电子发射的同步辐射是利用红外相机测量,但是红外相机的光路成本高,相机本身也比较昂贵.通过分析KSTAR装置逃逸电子的同步辐射功率谱,研究了逃逸电子同步辐射波长与能量的关系,拟发展新型的逃逸电子诊断系统.     

磁逆Compton散射谱与γ射线暴辐射机制

强弱场中相对论电子的逆Ｃｏｍｐｔｏｎ散射,即磁逆Ｃｏｍｐｔｏｎ散射,昊体高能辐射的一种重要辐射机制,本文利用磁逆Ｃｏｍｐｔｏｎ散射的半径典量子理论的回旋共振散射微分截面公式,采用相对论变换方法,计算了磁中子星表面附近的磁逆Ｃｏｍｐｔｏｎ散射的能谱,并作了相应的能谱图,与γ射线暴的观测能谱符合得很好。     

Ultra-relativistic electrons in Jupiter's radiation belts

Ground-based observations have shown that Jupiter is a two-component source of microwave radio emission: thermal atmospheric emission and synchrotron emission from energetic electrons spiralling in Jupiter's magnetic field. Later in situ measurements confirmed the existence of Jupiter's high-energy electron-radiation belts, with evidence for electrons at energies up to 20[?]MeV. Although most radiation belt models predict electrons at higher energies, adiabatic diffusion theory can account only for energies up to around 20[?]MeV. Unambiguous evidence for more energetic electrons is lacking. Here we report observations of 13.8[?]GHz synchrotron emission that confirm the presence of electrons with energies up to 50[?]MeV; the data were collected during the Cassini fly-by of Jupiter. These energetic electrons may be repeatedly accelerated through an interaction with plasma waves, which can transfer energy into the electrons. Preliminary comparison of our data with model results suggests that electrons with energies of less than 20[?]MeV are more numerous than previously believed.     

Fast acceleration of “killer” electrons and energetic ions by interplanetary shock stimulated ULF waves in the inner magnetosphere

Energetic electrons and ions in the Van Allen radiation belt are the number one space weather threat. Understanding how these energetic particles are accelerated within the Van Allen radiation belt is one of the major challenges in space physics. This paper reviews the recent progress on the fast acceleration of "killer" electrons and energetic ions by ultralow frequency (ULF) waves stimulated by the interplanetary shock in the inner magnetosphere. Very low frequency (VLF) wave-particle interaction is considered to be one of the primary electron acceleration mechanisms because electron cyclotron resonances can easily occur in the VLF frequency range. Recently, using four Cluster spacecraft observations, we have found that, after interplanetary shocks impact the Earth’s magnetosphere, energetic electrons in the radiation belt are accelerated almost immediately and continue to accelerate for a few hours. The time scale (a few days) for traditional acceleration mechanisms, based on VLF wave-particle interactions to accelerate electrons to relativistic energies, is too long to explain our observations. Furthermore, we have found that interplanetary shocks or solar wind pressure pulses, with even small dynamic pressure changes, can play a non-negligible role in radiation belt dynamics. Interplanetary shocks interaction with the Earth’s magnetosphere manifests many fundamental space physics phenomena including energetic particle acceleration. The mechanism of fast acceleration of energetic electrons in the radiation belt responding to interplanetary shock impacts consists of three contributing parts: (1) the initial adiabatic acceleration due to strong shock-related magnetic field compression; (2) followed by the drift-resonant acceleration with poloidal ULF waves excited at different L-shells; and (3) particle acceleration due to the quickly damping electric fields associated with ULF waves. Particles end up with a net acceleration because they gain more energy in the first half of this cycle than they lose in the second. The results reported in this paper cast a new light on understanding the acceleration of energetic particles in the Earth’s Van Allen radiation belt. The results of this study can likewise be applied to interplanetary shock interaction with other planets such as Mercury, Jupiter, Saturn, Uranus and Neptune, and other astrophysical objects with magnetic fields.     

Wave acceleration of electrons in the Van Allen radiation belts

The Van Allen radiation belts are two regions encircling the Earth in which energetic charged particles are trapped inside the Earth's magnetic field. Their properties vary according to solar activity and they represent a hazard to satellites and humans in space. An important challenge has been to explain how the charged particles within these belts are accelerated to very high energies of several million electron volts. Here we show, on the basis of the analysis of a rare event where the outer radiation belt was depleted and then re-formed closer to the Earth, that the long established theory of acceleration by radial diffusion is inadequate; the electrons are accelerated more effectively by electromagnetic waves at frequencies of a few kilohertz. Wave acceleration can increase the electron flux by more than three orders of magnitude over the observed timescale of one to two days, more than sufficient to explain the new radiation belt. Wave acceleration could also be important for Jupiter, Saturn and other astrophysical objects with magnetic fields.     

Anti-planetward auroral electron beams at Saturn

Strong discrete aurorae on Earth are excited by electrons, which are accelerated along magnetic field lines towards the planet. Surprisingly, electrons accelerated in the opposite direction have been recently observed. The mechanisms and significance of this anti-earthward acceleration are highly uncertain because only earthward acceleration was traditionally considered, and observations remain limited. It is also unclear whether upward acceleration of the electrons is a necessary part of the auroral process or simply a special feature of Earth's complex space environment. Here we report anti-planetward acceleration of electron beams in Saturn's magnetosphere along field lines that statistically map into regions of aurora. The energy spectrum of these beams is qualitatively similar to the ones observed at Earth, and the energy fluxes in the observed beams are comparable with the energies required to excite Saturn's aurora. These beams, along with the observations at Earth and the barely understood electron beams in Jupiter's magnetosphere, demonstrate that anti-planetward acceleration is a universal feature of aurorae. The energy contained in the beams shows that upward acceleration is an essential part of the overall auroral process.     

实验室坐标系下的磁逆康普顿散射

利用实验室坐标系磁Compton散射截面公式，对谱函数进行了更精确的计算，结果表明，除了原谱函数的共振项系数有修正外，还得到了一个直接依赖于磁场的项，当磁场较弱时，它的贡献不可忽略，这是一个新的结果，它不可能由Herold的结果通过相对论变换而得到。