The solar wind is a magnetized plasma and as such exhibits collective plasma behavior associated with its characteristic spatial and temporal scales. The characteristic length scales include the size of the heliosphere, the collisional mean free paths of all species, their inertial lengths, their gyration radii, and their Debye lengths. The characteristic timescales include the expansion time, the collision times, and the periods associated with gyration, waves, and oscillations. We review the past and present research into the multi-scale nature of the solar wind based on in-situ spacecraft measurements and plasma theory. We emphasize that couplings of processes across scales are important for the global dynamics and thermodynamics of the solar wind. We describe methods to measure in-situ properties of particles and fields. We then discuss the role of expansion effects, non-equilibrium distribution functions, collisions, waves, turbulence, and kinetic microinstabilities for the multi-scale plasma evolution.

太阳风是磁化等离子体，因此表现出与其特征空间和时间尺度相关的集体等离子体行为。特征长度尺度包括日光层的大小、所有物种的碰撞平均自由程、它们的惯性长度、它们的回转半径和它们的德拜长度。特征时间尺度包括膨胀时间、碰撞时间以及与回转、波浪和振荡相关的周期。我们回顾了基于原位航天器测量和等离子体理论对太阳风多尺度性质的过去和现在的研究。我们强调，跨尺度过程的耦合对于太阳风的全球动力学和热力学非常重要。我们描述了测量粒子和场的原位特性的方法。然后我们讨论膨胀效应、非平衡分布函数、碰撞、波、湍流和动力学微观不稳定性对多尺度等离子体演化的作用。