土星磁层中尘埃离子声dromions
Dust ion-acoustic dromions in Saturn's magnetosphere
摘要：
受卡西尼号和旅行者1号、2号探测器在土星磁层中观测到的局部静电波包的启发，我们研究了土星尘埃等离子体环境中局部多维结构的存在条件和动力学演化。为此，我们采用了等离子体流体模型的尘埃离子声（DIA）的激发，考虑到存在的高能量（超热，卡帕分布）电子人口结合大量的尘埃颗粒的背景。多尺度微扰方法表明，导致Davey-Stewartson（DS）系统的演化方程，如果一个假设垂直的载波传播的磁场（方向）。然后，该系统被证明具有两个政权主要，在文献中称为DS-I和DS-II。在前一种情况下，如果满足某些条件，则获得指数局部解，称为dromion。各种物理参数，如电子光谱指数，环境磁场（强度），和粉尘浓度的综合影响进行了研究。数值研究表明，dromion振幅增加与更高的尘埃浓度，而它降低较低的$κ_e$（即在超热电子的人口组成部分的增加）。较强的磁场导致较高的振幅但较窄的dromion。我们的研究结果提供了一个全面的框架建模调制静电波包，在行星环境中的实验数据直接比较，在土星的磁层，和其他地方。
英文摘要：
Motivated by observations of localized electrostatic wavepackets by the Cassini and (earlier) by Voyager 1 and 2 mission(s) in Saturn's magnetosphere, we have investigated the existence conditions and the dynamical evolution of localized multi-dimensional structures in the Saturnian dusty plasma environment. To this effect, we have adopted a plasma-fluid model for dust-ion acoustic (DIA) excitations, taking into account the presence of a highly energetic (suprathermal, kappa-distributed) electron population in combination with massive dust particulates in the background. A multiple scales perturbation method was shown to lead to a Davey-Stewartson (DS) system of evolution equations, if one assumes perpendicular carrier wave propagation across the magnetic field (direction). The system is then shown to possess two regimes mainly, known in the literature as DS-I and DS-II. In the former case, if certain conditions are fulfilled, exponentially localized solutions are obtained, known as dromions. The combined effects of various physical parameters such as the electron spectral index, the ambient magnetic field (strength), and the dust concentration have been examined. A numerical investigation reveals that the dromion amplitude increases with higher dust concentration, while it decreases for lower $κ_e$ (i.e. with an increase in the suprathermal electron population component). A stronger magnetic field results in higher amplitude but narrower dromions. Our results provide a comprehensive framework for modeling modulated electrostatic wavepackets, in direct comparison with experimental data in planetary environments, in Saturn's magnetosphere, and elsewhere.
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