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太阳耀斑伽玛射线能谱是加速粒子与太阳大气介质原子碰撞的结果,它是研究太阳耀斑中加速粒子和高能电子最为直接的手段.通过分析伽玛射线能谱,可以获得耀斑过程中加速粒子的成分、能谱、角分布及太阳大气元素丰度等重要信息.TALYS程序是一套模拟核反应的软件,对核反应过程中的所有信息均能完整地描述.利用TALYS计算得到了完整的太阳耀斑伽玛射线的核反应截面数据,开发了一套新的耀斑伽玛射线谱计算程序.详细介绍了耀斑伽玛射线计算的理论模型,并简单探讨了耀斑伽玛射线的特性,为未来的耀斑伽玛射线能谱分析奠定了理论基础. 相似文献
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为了解释日冕中高能电子束和太阳耀斑中的快速过程,本文提出在活动区双极黑子上空存在一个准开放磁场线区域的定性模型。如图1所示,准开放磁场线区域被确定在开放磁场线下面和耀斑环顶部之间。 由于那里的快速磁重联或撕裂、爆炸式的能量释放引起了区域性的等离子体加速。那些被加速到10—100keV的高能电子束沿着开放的磁场线从太阳大气等离子体逃逸到行星际等离子体中。在每个连续的高度上将产生朗缪尔波等离子体辐射。朗缪尔波同低 相似文献
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磁重联在宇宙的许多动力学现象中都是非常核心的过程.磁流体动力学(MHD)数值模拟是研究磁重联过程以及相应物理图像的一种很有效的手段.通过不同的参数组合,来研究MHD数值模拟中磁雷诺数和空间分辨率对磁重联率、数值耗散和能谱分布的影响.对得到的数据进行分析后,发现磁雷诺数对磁重联率和能谱分布有一定的影响.磁雷诺数越大,磁重联过程进入非线性阶段所需的特征时间越短,磁重联率就越早发生跃升.磁雷诺数Rm对耗散开始发挥作用的Kolmogorov微观尺度lko有明显影响:Rm越大,lko就越小.研究了磁重联过程中包括数值耗散在内的额外耗散对重联过程的影响.结果表明,撕裂模不稳定性开始之前的额外耗散以纯数值耗散为主,撕裂模不稳定性出现之后,额外耗散出现同步跃升,说明不稳定性导致的湍流明显增强了耗散的效果,相当于在局部湍流区引入了超电阻.能谱分析进一步表明,大尺度电流片的lko完全可能出现在宏观的MHD尺度上. 相似文献
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该文通过综述相关研究成果,对日冕亮点的观测特征和供能机制进行了总结和评论.日冕亮点是发生在过渡区和低日冕的小尺度局地增亮现象,经常在X射线和极紫外波段观测到,其寿命在5～40 h之间.日冕亮点的产生和演化与双极磁场的相互作用紧密相关.对于日冕亮点的供能机制,目前主要存在三种观点:(1)磁场对消的观点,当不同极性的磁场区域相互靠近时,局地发生磁重联,并在重联区域加热等离子体,从而导致X射线和极紫外辐射的增强;(2)分隔线重联,与日冕亮点相联系的磁场结构可以形成分隔线重联位形,沿分隔线的快速磁场重联导致过渡区和日冕局地的等离子体被加热,从而产生日冕亮点;(3)光球水平运动所诱发的电流片为亮点提供了能量来源.近期研究表明,三种机制可能同时作用,为亮点提供所需的能量. 相似文献
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《天文学报》2015,(6)
日冕物质抛射(Coronal Mass Ejection,CME)通常会将其后面区域中的磁场急剧拉伸,使得极性相反的磁力线相互靠近而形成磁重联电流片.磁重联电流片在爆发过程中,既是磁自由能迅速转化为热能、等离子动能和高能粒子束流的重要区域,又起着连接日冕物质抛射和耀斑的作用.2003年1月3日和11月4日的两次CME事件,在CME离开太阳表面附近之后,均有电流片被观测到.结合搭载在SOHO(Solar and Heliospheric Observatory)上的LASCO(Large Angle and Spectrometric Coronagraph)、UVCS(Ultraviolet Coronagraph Spectrometer)数据,以及大熊湖天文台和云南天文台的Hα资料,研究两次爆发事件的动力学特征,以及电流片的物理特性.电流片中高电离度粒子的存在,如Fe~(+17)、Si~(+11),表明电流片区域中温度高达3×10~6～5×10~6K.直接测量发现电流片的厚度在1.3×10~4～1.1×10~5km范围之间,并随时间先增大后逐渐减小.利用CHIANTI(ver 7.1)光谱代码,进一步计算得到2003年1月3日电流片中的电子温度和相应辐射量(Emission Measure,EM)的均值分别为3.86×10~6K和6.1×10~(24)cm~(-5).另一方面,利用SOHO/UVCS观测数据对2003年11月4日的CME爆发事件中的电流片进行分析,发现电流片呈现准周期性扭转运动. 相似文献
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本文从粒子分布函数所满足的带有规则电场的准线性方程出发,得到了包含有规则电场与湍动起伏场相互耦合作用在内的等效动量空间扩散系数,提出了太阳质子耀斑中性片中的规则电场与湍动起伏场的联合加速机制。根据太阳质子耀斑的物理条件,计算表明荷电粒子在中性片中可以被有效地加速,能量可以达到～20MeV,甚至～1GeV。本文证明了离子声湍动起伏场与规则电场的联合加速机制有效地使质子和其它重离子注入到Langmuir湍动加速区中去;并且表明,在Langmuir湍动起伏场与规则电场联合加速的情形下,可以得到与观测事实符合得较好的高能质子的谱以及高能电子的幂律分布的谱。 相似文献
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对一个太阳风暴及其行星际和地磁效应的研究 总被引：1，自引：0，他引：1
对一个爆发于2014年1月7日的太阳风暴进行了研究,通过对太阳活动的多波段遥感观测—来自于太阳动力学天文台(Solar Dynamics Observatory,SDO)以及太阳和日球天文台(Solar and Heliospheric Observatory,SOHO),分析了耀斑和日冕物质抛射(coronal mass ejection,CME)的爆发过程.通过地球同步轨道环境业务卫星(Geostationary Operational Environmental Satellites,GOES)对高能质子以及日地L1点的元素高级成分探测器(Advanced Composition Explorer,ACE)对当地等离子体环境的就位观测,分析了伴随太阳风暴的太阳高能粒子(solar energetic particle,SEP)事件和行星际CME(ICME)及其驱动的激波.通过地面磁场数据分析了该太阳风暴对地磁场的影响.研究结果表明:(1)耀斑脉冲相的开始时刻和CME在日面上的抛射在时序上一致.(2)高能质子主要源于CME驱动的激波加速,并非源于耀斑磁重联过程.质子的释放发生在CME传播到7.7个太阳半径的高度的时刻.(3)穿过近地空间的行星际激波鞘层的厚度和ICME本身的厚度分别为0.22 au和0.26 au.(4)行星际激波和ICME引起了多次地磁亚暴和极光,但没有产生明显的地磁暴.原因在于ICME没有包含一个规则的磁云结构或明显的南向磁场分量. 相似文献
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《天文学进展》2016,(4)
作为汪景琇院士主持的中国科学院数理学部"天体辐射磁流体力学"战略研究项目组成部分~([1]),从等离子体的动力学属性出发,介绍了用于研究等离子体与周围磁场结构相互作用的粒子云网格方法,及其在研究具有复杂等离子体和磁场结构的磁重联过程中的应用。这里提到的磁场与等离子体的复杂性包括变化的等离子体β值,磁重联电流片中包含有多种尺度的结构,以及这些结构之间的相互作用,而且这些结构的尺度变化范围很大(从105km变化到102km)。进一步探讨了该方法在太阳物理领域,特别是在太阳爆发磁重联过程方面的可能应用以及未来的发展;并为项目研究中其他部分在数值方法~([2–5])和太阳物理~([6,7])方面提供借鉴和补充。 相似文献
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太阳空间观测揭示出太阳的高能电子,高能质子发射以及γ射线爆发。证实了有关的太阳射电辐射理论,揭示出太阳耀斑中的核反应。日冕物质抛射和耀斑等离子体云的空间观测揭示出它们之间的区别和联系,认识到耀斑的热区和冷区。在阳和日球磁场以观测发展了磁流体动力学理论。 相似文献
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By the test particle method, we have investigated the kinematic characteristics of the electrons in the reconnecting current sheet with a guiding magnetic field Bz after they are accelerated by the supper-Dreicer electric field Ez. Firstly, the influence of the guiding magnetic field Bz on the particle acceleration is discussed under the assumption that Bz is constant in magnitude but different in orientation with respect to the electric field. In this case, the variation of the Bz direction directly leads to the variation of electron trajectories and makes electrons leave the current sheet along different paths. If Bz is parallel to Ez, the pitch angles of the accelerated electrons are close to 180°. If Bz is anti-parallel to Ez, the pitch angles of the accelerated electrons are close to 0°. The orientation of the guiding magnetic field just makes the electric field accelerate selectively the electrons in different regions, but does not change the energy distribution of electrons, and the finally derived energy spectrum is the common power-law spectrum E?γ. In typical coronal conditions, γ is about 2.9. The further study indicates that the magnitude of γ depends on the strengths of the guiding magnetic field and reconnecting electric field, as well as the scale of the current sheet. Then, the kinematic characteristics of the accelerated electrons in the current sheet with multiple X-points and O-points are also studied. The result indicates that the existences of the X-points and O-points have the particles constrained in the accelerating region to obtain the maximum acceleration, and the final energy spectrum has the characteristics of multi-power law spectra. 相似文献
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Valentina V. Zharkova Mykola Gordovskyy 《Monthly notices of the Royal Astronomical Society》2005,356(3):1107-1116
Electron and proton acceleration by a super-Dreicer electric field is investigated in the non-neutral reconnecting current sheet (RCS) with a non-zero longitudinal component of the magnetic field ('guiding field'). The guiding field is assumed parallel to the direction of electric field and constant within an RCS. The other two magnetic field components, transverse and tangential, are considered to vary with distances from the X null point of an RCS. The proton and electron energy spectra are calculated numerically from a motion equation using the test particle approach for model RCSs with constant and variable densities. In the presence of a strong or moderate guiding field, protons were found fully or partially separated from electrons at ejection from an RCS into the opposite, 'electron' and 'proton', semiplanes. In the case of a weak guiding field, both protons and electrons are ejected symmetrically in equal proportions as neutral beams. The particles ejected from an RCS with a very weak or very strong guiding field have power-law energy spectra with spectral indices of about 1.5 for protons and 2.0 for electrons. For a moderate guiding field, the energy spectra of electrons ejected into the opposite semiplanes are mixed, i.e. in the 'electron-dominated' semiplane power-law energy spectra for electrons and thermal-like for protons, while in the 'proton' semiplane they are symmetrically mirrored. 相似文献
13.
Acceleration of Electrons and Protons in Reconnecting Current Sheets Including Single or Multiple X-points 总被引：1，自引：0，他引：1
Kinematic characteristics of electrons and protons in the magnetic reconnecting current sheet in the presence of a guide field are investigated. Particle trajectories are calculated for different values of the guide field by a test-particle calculation. The relationship between the final energy and the initial position has also been studied. We found that the addition of a guide field not only allows particles to get more energy and not only results in the separation of electrons and protons, but also causes the reconnecting electric field to selectively accelerate electrons and protons for different initial positions. The energy spectrum eventually obtained is the common power-law spectrum, and as the guide field increases, the index for the spectrum of electrons decreases rapidly. However, for a weak background magnetic field, proton spectra are not very sensitive to the guide field; but for a strong background field, the dependence of the spectrum index is similar to the electron spectrum. Meanwhile, kinematic characteristics of the accelerated particles in the current sheet including multiple X-points and O-points were also investigated. The result indicates that the existence of the multiple X- and O-points helps particles trapped in the accelerating region to gain more energy, and yields the double or multiple power-law feature. 相似文献
14.
《Chinese Astronomy and Astrophysics》1983,7(2):124-129
Starting with the quasi-linear equation of the distribution function of particles in a regular electric field, a combined diffusion coefficient in the momentum space conbining the effects of the regular field and a turbulent field is obtained and a combined mechanism of acceleration by the regular and turbulent fields in the neutral sheet of solar proton flares is proposed. It is shown by calculation that conditions in solar proton flares are such that the charged particles can be effectively accelerated to tens of MeV, even ~1 GeV. It is shown that the combined acceleration by a regular electric field and ion-acoustic turbulence pumps the protons and other heavy ions into ranges of energy where they can be accelerated by Langmuir turbulence. By considering the combined acceleration by Langmuir turbulence and the regular electric field, the observed spectrum of energetic protons and the power-law spectrum of energetic electrons can be reproduced. 相似文献
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C. Gontikakis C. Efthymiopoulos A. Anastasiadis 《Monthly notices of the Royal Astronomical Society》2006,368(1):293-304
We consider the possibility of particles being injected at the interior of a reconnecting current sheet (RCS), and study their orbits by dynamical systems methods. As an example we consider orbits in a 3D Harris type RCS. We find that, despite the presence of a strong electric field, a 'mirror' trapping effect persists, to a certain extent, for orbits with appropriate initial conditions within the sheet. The mirror effect is stronger for electrons than for protons. In summary, three types of orbits are distinguished: (i) chaotic orbits leading to escape by stochastic acceleration, (ii) regular orbits leading to escape along the field lines of the reconnecting magnetic component, and (iii) mirror-type regular orbits that are trapped in the sheet, making mirror oscillations. Dynamically, the latter orbits lie on a set of invariant KAM tori that occupy a considerable amount of the phase space of the motion of the particles. We also observe the phenomenon of 'stickiness', namely chaotic orbits that remain trapped in the sheet for a considerable time. A trapping domain, related to the boundary of mirror motions in velocity space, is calculated analytically. Analytical formulae are derived for the kinetic energy gain in regular or chaotic escaping orbits. The analytical results are compared with numerical simulations. 相似文献
16.
Electron and proton acceleration in reconnecting current sheets in electron-rich solar flares is considered. A significant three-dimensional magnetic field is assumed in the current sheet where the particles are accelerated by the DC electric field. The tearing instability of a pre-flare current sheet leads to the formation of multiple singular lines of magnetic field where the electric and magnetic fields are coaligned. Magnetized electrons are shown to be accelerated to a few tens of MeV before they leave the vicinity of a singular line. The acceleration time is estimated to be less than 10–3 s. By contrast, much heavier protons are unmagnetized and their energy gain is more modest. The model explains a high electron-to-proton ratio and the unusually intense gamma-ray continuum above 1 MeV observed in the electron-rich flares. 相似文献
17.
G. D. Fleishman 《Astronomy Letters》2004,30(9):603-614
We studied the spectral properties of the electron cyclotron maser emission generated by anisotropic distributions of fast electrons with power-law magnitude distributions in solar flares. The natural bandwidth of the generated spectral line depends significantly on the angle between the direction of the wave emission and the direction of the magnetic field in the source. In addition, the line bandwidth depends on the parameters of the momentum and pitch-angle distribution functions for fast electrons. The typical spectral bandwidths are shown to lie within the range 0.1–0.4%, in agreement with the minimum observable bandwidths of millisecond solar radio spikes. 相似文献
18.
A system of multi-fluid MHD-equations is used to compare adiabatic and non-adiabatic transport of the energetic particles in the magnetospheric plasma sheet. A “slow-flow” approximation is considered to study large-scale transport of the anisotropic plasma consisting of energetic electrons and protons. Non-adiabatic transport of the energetic plasma is caused by scattering of the particles in the presence of both wave turbulence and arbitrary time-varying electric fields penetrating from the solar wind into the magnetosphere. The plasma components are devided into particle populations defined by their given initial effective values of the magnetic moment per particle. The spatial scales are also given to estimate the non-uniformity of the geomagnetic field along the chosen mean path of a particle. The latters are used to integrate approximately the system of MHD-equations along each of these paths. The behaviour of the magnetic moment mentioned above and of the parameter which characterizes the pitch-angle distribution of the particles are studied self-consistently in dependence on the intensity of non-adiabatic scattering of the particles. It is shown that, in the inner magnetosphere, this scattering influences the particles in the same manner as pitch-angle diffusion does. It reduces the pitch-angle anisotropy in the plasa. The state of the plasma may be unstable in the current sheet of the magnetotail. If the initial state of the plasma does not correspond to the equilibrium one, then, in this case, scattering influences the particles so as to remove the plasma further from the equilibrium state. The coefficient of the particle diffusion across the geomagnetic field lines is evaluated. This is done by employing the Langevin approach to take the stochastic electric forces acting on the energetic particles in the turbulent plasma into account. The behaviour of the energy density of electrostatic fluctuations in the magnetosphere is estimated. 相似文献
19.
V. V. Zaitsev 《Astronomy Letters》2005,31(9):620-626
We analyze the electric fields that arise at the footpoints of a coronal magnetic loop from the interaction between a convective flow of partially ionized plasma and the magnetic field of the loop. Such a situation can take place when the loop footpoints are at the nodes of several supergranulation cells. In this case, the neutral component of the converging convective flows entrain electrons and ions in different ways, because these are magnetized differently. As a result, a charge-separating electric field emerges at the loop footpoints, which can efficiently accelerate particles inside the magnetic loop under appropriate conditions. We consider two acceleration regimes: impulsive (as applied to simple loop flares) and pulsating (as applied to solar and stellar radio pulsations). We have calculated the fluxes of accelerated electrons and their characteristic energies. We discuss the role of the return current when dense beams of accelerated particles are injected into the corona. The results obtained are considered in light of the currently available data on the corpuscular radiation from solar flares. 相似文献
20.
N.A. Tsyganenko 《Planetary and Space Science》1982,30(5):433-437
An investigation of pitch-angle scattering of energetic particles in magnetic field configurations with a current sheet similar to that observed in the geomagnetotail has been performed. The magnetic field model is specified by two parameters which are the current sheet thickness in units of particle gyroradius and the angle between the magnetic field lines and the sheet plane. Computations of a considerable number of trajectories (about 20,000 for each model case) has provided the possibility of obtaining the matrix of pitch-angle scattering and the corresponding kernel function of the integral equation for the stationary particle distribution function. Solution of this equation shows that isotropic distributions are formed only in the case of a sufficiently thick current sheet. Particle scattering in a thin field reversal region leads to the formation of an anisotropic stationary distribution. The results can be used for interpretation of the data on the spatial distribution of energetic particle fluxes in the near part of the magnetospheric tail and in the vicinity of the outer boundary of the radiation belt. 相似文献