Electron Distribution in the Solar Wind from the Sun to the Earth

太阳风是一股热的电离气体，或等离子体，从日冕膨胀到行星际介质。自1959年发现以来，空间科学家一直在研究太阳风中质子和电子的行为，它们与星际空间磁场的相互作用，以及与行星磁层的相互作用。大约在同一时间，等离子体物理学家正在考虑包含比日冕热一百倍的等离子体，以获得受控的聚变反应-一种几乎取之不尽的相对清洁和安全的能源。他们提出了所谓的镜像机器，这是一种磁性结构，类似于一个两端有两个开口的瓶子。然而，这种装置并不理想-热等离子体可能通过瓶颈开口泄漏并从约束室流出。 这个项目建立了等离子体逃离镜机和等离子体从热的太阳日冕膨胀之间的类比。它将利用在等离子体聚变研究中形成的理论框架来解释太阳风中电子的行为，这是空间等离子体物理学的基本问题之一。 该项目研究太阳风等离子体从炽热的日冕中膨胀。它解决了以下问题：给定日冕附近的电子分布函数，在更大的日光层距离的分布函数是什么？该项目建立了与等离子体镜机的类比。类似于镜机扩展器，太阳风电子分布函数包含一束电子流沿着磁场线和一个准各向同性核心，一方面，是从束散射的电子，另一方面，提供散射的电子流。该项目开发了一个新的自洽的理论框架来解决这个问题。研究结果将是电子分布与径向距离的函数关系。这将使人们能够理解，特别是，在背景等离子体中的径向能量转移和能量沉积，在膨胀区域中的等离子体温度分布，电子不稳定性和由此产生的等离子体湍流。结果将与现有的观测结果进行比较，特别是，可能是有价值的帕克太阳探测器数据的解释。这个奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

The solar wind is a stream of hot ionized gas, or plasma, expanding from the solar corona into the interplanetary medium. Since its discovery in 1959, space scientists have been studying the behavior of protons and electrons in the solar wind, their interaction with the magnetic fields pervading interstellar space, and with magnetospheres of planets. At approximately the same time, plasma physicists were thinking about containing plasma that is a hundred times hotter than that in the solar corona, to obtain controlled fusion reaction – a virtually inexhaustible source of relatively clean and safe energy. They came up with the so-called mirror machine, a magnetic configuration resembling a bottle with two openings at the opposite ends. However, such a device was not ideal – hot plasma could leak through the bottleneck openings and stream away from the confinement chamber. This project establishes the analogy between the plasma escaping the mirror machine and the plasma expanding from the hot solar corona. It will use the theoretical framework developed in plasma fusion studies to explain the behavior of electrons in the solar wind, one of the fundamental problems of space plasma physics. The project studies the solar wind plasma expanding from the hot solar corona. It addresses the following question: given the electron distribution function near the solar corona, what is the resulting distribution function at larger heliospheric distances? The project establishes the analogy with the plasma mirror machines. Similarly to the mirror-machine expander, the solar wind electron distribution function contains a beam of electrons streaming along the magnetic field lines and a quasi-isotropic core that, on one hand, is related to the electrons scattered from the beam and on the other, provides scattering for the streaming electrons. The project develops a new self-consistent theoretical framework for solving this problem. The outcome of the study will be the electron distribution as a function of radial distance. This will allow one to understand, in particular, the radial energy transfer and energy deposition in the background plasma, the plasma temperature profile in the expansion region, the electron instabilities and the resulting plasma turbulence. The results will be compared with available observations, and in particular, may be valuable for the interpretation of the Parker Solar Probe data.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.