Zirnstein E J, Giacalone J, Kumar R, McComas D J, Dayeh M A, Heerikhuisen J
Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544, USA.
Department of Planetary Sciences, University of Arizona, Tucson, AZ 85721, USA.
Astrophys J. 2020 Jan 1;888(1). doi: 10.3847/1538-4357/ab594d.
The effects of turbulence in the very local interstellar medium (VLISM) have been proposed by Giacalone & Jokipii (2015) to be important in determining the structure of the () ribbon via particle trapping by magnetic mirroring. We further explore this effect by simulating the motion of charged particles in a turbulent magnetic field superposed on a large-scale mean field, which we consider to be either spatially-uniform or a draped field derived from a 3D MHD simulation. We find that the ribbon is not double-peaked, in contrast to Giacalone & Jokipii (2015). However, the magnetic mirror force still plays an important role in trapping particles. Furthermore, the ribbon's thickness is considerably larger if the large-scale mean field is draped around the heliosphere. observations in the VLISM show a turbulent field component that is stronger than previously thought, which we test in our simulation. We find that the inclusion of turbulent fluctuations at scales ≳100 au and power consistent with observations produces a ribbon whose large-scale structure is inconsistent with observations. However, restricting fluctuations to <100 au produces a smoother ribbon structure similar to observations. Different turbulence realizations produce different small-scale features (≲10°) in the ribbon, but its large-scale structure is robust if the maximum fluctuation size is ≲50 au. This suggests that the magnetic field structure at scales ≲50 au is determined by the heliosphere-VLISM interaction and cannot entirely be represented by pristine interstellar turbulence.
贾卡洛内和乔基皮伊（2015年）提出，本地星际介质（VLISM）中的湍流效应对于通过磁镜捕获粒子来确定（）带的结构很重要。我们通过模拟带电粒子在叠加于大尺度平均场上的湍流磁场中的运动，进一步探究这种效应，我们认为该大尺度平均场要么是空间均匀的，要么是从三维磁流体动力学模拟得出的包层场。我们发现，与贾卡洛内和乔基皮伊（2015年）的研究结果相反，该带不是双峰的。然而，磁镜力在捕获粒子方面仍然起着重要作用。此外，如果大尺度平均场围绕日球层分布，那么该带的厚度会大得多。VLISM中的观测显示，湍流场分量比之前认为的更强，我们在模拟中对此进行了检验。我们发现，纳入尺度≳100天文单位且功率与观测结果一致的湍流涨落，会产生一个其大尺度结构与观测结果不一致的带。然而，将涨落限制在<100天文单位会产生一个与观测结果类似的更平滑的带结构。不同的湍流实现方式会在带中产生不同的小尺度特征（≲10°），但其大尺度结构如果最大涨落尺寸≲50天文单位则是稳健的。这表明，尺度≲50天文单位的磁场结构由日球层 - VLISM相互作用决定，不能完全由原始星际湍流来表示。
