Solar Particle Transport in a Dynamical Quasi-linear Theory
Solar Particle Transport in a Dynamical Quasi-linear Theory
复制标题
动力学拟线性理论中的太阳粒子输运
DOI：
10.1086/374812
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发表时间：
2003
期刊：
影响因子：
--
通讯作者：
W. Dröge
中科院分区：
文献类型：
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作者：
W. Dröge
目前高能粒子在日光层中平行扩散的理论被相当好地接受，并得到观测和模拟结果的支持，如果考虑到最近发现的由部分平板和部分二维复合几何组成的磁涨落的证据。然而，在中低能，太阳风中的动力效应，如波的传播和热阻尼，以及磁涨落的随时间变化的去相关，对散射平均自由程有很大的影响，这是一个重要的悬而未决的问题。提出了一个解决上述影响的模型，并能够解释从keV电子到GeV质子的粒子平均自由程与观测到的刚性的关系。在低刚性下导致90°强非共振俯仰角散射的动力学过程可以用单个参数来描述，该参数由太阳风中观测到的密度、温度和磁场强度决定。这使得在粒子散射中最有效的波动的板材含量成为唯一剩余的输入参数。对太阳粒子事件确定的电子和质子的平均自由程与根据事件期间观测到的磁场波动对板条分量的估计的模型的预测进行了比较。我们发现，该模型很好地再现了观测结果，这表明太阳粒子输运和太阳风湍流性质之间的逐个事件基础上的关系终于成为可能。讨论了日光层中其他高能粒子过程的后果，以及使用太阳电子探测航天器无法进入的区域的太阳风湍流特性的可能性。
Current theories for parallel diffusion of high-energy particles in the heliosphere are fairly well accepted, and supported by both observations and simulation results, if recently found evidence for the magnetic fluctuations consisting of a partly slab and partly two-dimensional composite geometry is taken into account. However, there are important outstanding questions pertaining at medium to low energies where dynamical effects in the solar wind, such as propagation and thermal damping of waves, and time-dependent decorrelation of magnetic fluctuations, have a strong influence on the scattering mean free path. A model is presented that addresses the above effects and is able to explain the observed rigidity dependence of particle mean free paths ranging from keV electrons to GeV protons. The dynamical processes, leading to a strongly nonresonant pitch-angle scattering through 90° at low rigidities, can be described by a single parameter that is determined from the observed density, temperature, and magnetic field strength in the solar wind. This leaves the slab content of the fluctuations, which is most effective in particle scattering, as the only remaining input parameter. Mean free paths for electrons and protons determined for a solar particle event were compared with predictions from the model based on an estimate of the slab component from magnetic field fluctuations observed during the time of the event. We find that the model reproduces the observations well, suggesting that a relation between the properties of solar particle transport and of solar wind turbulence on an event-by-event basis has finally become possible. Consequences for other energetic particle processes in the heliosphere and possibilities to use solar electrons to probe properties of the solar wind turbulence in regions not accessible by spacecraft are discussed.