Solar Accelerated Electron Beam-Plasma Interactions in our Solar System

太阳的外层大气极不稳定。频繁的爆炸将粒子束加速到接近光速，并周期性地驱逐出大量的质量，这就是太阳风暴。活跃的太阳对地球的影响被称为太空天气。了解这些粒子束的加速和传输是一项重要的现代挑战，以前由于缺乏太阳附近的航天器测量而受到阻碍。该项目的目标是利用来自尖端航天器和先进模拟的数据组合程序，了解这些粒子束在穿越太阳系的旅程中是如何演变的。美国宇航局的帕克太阳探测器（2018年发射）和欧洲航天局的太阳轨道飞行器（2020年发射）正在进行近太阳等离子体测量的新前沿，它们都比以往任何时候都更接近太阳。这些航天器在太阳风中飞行，太阳风是太阳不断流出的热等离子体，遍布行星际空间。我们将量化电子束如何与太阳大气和太阳风中的波共振相互作用。这将包括测量近相对论性电子分布函数在离太阳许多不同距离上的时间演化。然后可以将粒子数据与局部电场的增加进行比较；光束产生的等离子体波的特征。新的测量将使我们能够测试现有理论的有效性，这些理论涉及电子能量损失、波的产生，以及两者如何受到太阳风湍流性质的影响。然后，我们将利用高性能的数值模拟来模拟电子的传输及其与等离子体波的相互作用。通过将我们尖端的太阳风数据测量作为模拟输入，我们将改进我们对电子如何在太阳系中失去能量和改变轨迹的理解。我们还将探索宇宙飞船无法进入的太阳大气层中的初始加速度特性。新的模型可以做出重要的预测，包括电子束到达地球的时间。此类输出可用于更新空间天气模型，帮助确保未来空间技术的安全。这种模拟和广泛观测的结合为人类对太阳如何工作以及它如何与我们的太阳系相互作用的认识和理解提供了一个令人兴奋的机会。

Our Sun's outer atmosphere is extremely unstable. Frequent explosions accelerate particle beams to near-light speeds, and periodically expel huge volumes of mass, known as solar storms. The effect of our active Sun on the Earth is known as space weather. Understanding the acceleration and transport of these particle beams is an important, modern challenge, previously hindered by a lack of spacecraft measurements near the Sun. The goal of this project is to understand how these particle beams evolve on their journey through the solar system using a combined programme of data from cutting-edge spacecraft and advanced simulations. A new frontier of near-Sun plasma measurements is being taken by NASA's Parker Solar Probe (launched 2018) and ESA's Solar Orbiter (launching 2020), both flying closer to the Sun than ever before. These spacecraft fly through the solar wind, hot plasma that continuously streams out from the Sun and populates the interplanetary space. We will quantify how electron beams resonantly interact with waves in the solar atmosphere and the solar wind. This will involve measuring the time evolution of the near-relativistic electron distribution function at many different distances from the Sun. The particle data can then be compared with increases in local electric fields; the signature of beam-generated plasma waves. The new measurements will allow us to test the validity of existing theories regarding electron energy loss, wave generation, and how both are affected by the turbulent nature of the solar wind. We will then utilise high-performance numerical simulations that model the transport of electrons and their interaction with plasma waves. By including our cutting-edge solar wind data measurements as simulations inputs, we will refine our understanding about how electrons lose energy and change trajectories through the solar system. We will also explore the initial acceleration characteristics in the solar atmosphere, where spacecraft are unable to enter. The new models can make important predictions, including the arrival times of electron beams at Earth. Such outputs can be used to update space weather models that help secure safety for future space technology. This combination of simulations and wide-ranging observations presents an exciting opportunity to significant progress human knowledge and understanding of how the Sun works, and how it interacts with our solar system.