Fundamental Wave-Plasma Processes

地球拥有一个磁场，其形状与一个简单的条形磁铁产生的磁场非常相似。磁力线从地球的一个磁极出现，并延伸出大气层，进入太空数千公里，然后返回到另一个半球的磁极。而不是真空，这些场线通过的空间区域充满了等离子体/由带电粒子组成的导电气体。这些粒子中的大多数源自地球大气层，是由紫外线阳光电离高海拔大气层/电离层区域中的气体产生的。太阳也有很强的磁场。由于核过程在太阳内部产生能量，太阳大气的外层通过太阳系向外膨胀，形成太阳风。当太阳风到达地球时，它与地球的磁场发生碰撞，并在地球周围转向。由地球磁场从太阳风中切割出来的空腔被称为磁层。在磁层内部，等离子体和磁场通常主要来自地球。在磁层之外，它们来自太阳。这些区域并不总是严格分开的，这导致了我们的行星和它最近的星星之间的电磁相互作用。电离层对通过它的无线电波有重大影响，而一些来自太阳风的高能粒子被困在环绕地球的辐射带中，距离在20，000 - 60，000公里之间，这是许多地球轨道卫星所占据的空间。在高纬度地区，带电粒子可以从辐射带逃逸到沉淀物中进入高层大气，在那里它们激发大气气体形成北极光（即“北方光”）。显然，这种太阳与地球的连接不仅导致了美丽的自然现象，而且还影响了我们所依赖的人造技术。据估计，宇宙中大约99%是等离子体。在这方面，太阳风、磁层和电离层并不是奇异的。然而，等离子体并不自然存在于地球表面。因此，如果我们要充分了解等离子体（以及宇宙的大部分）的行为，我们需要利用我们星球周围的天然等离子体实验室。一些最大的谜团围绕着等离子体和电磁波的相互作用。例如，波-等离子体相互作用（WPI）被认为是导致冷等离子体被激发的许多过程的原因。这些包括地球辐射带的形成或导致极光并可能损坏卫星的等离子体的加速。然而，人们对这些机制知之甚少。在地球环境中，波粒相互作用经常被用作粒子加速器内的一种激励机制。由WPI加热的人工产生和限制的等离子体位于实验聚变反应堆的核心，为未来的清洁能源提供了希望。显然，对波-等离子体相互作用的更好理解是至关重要的。一个五年的研究方案概述。它的主要目的是解决这个普遍相关的物理过程。通过在更接近地球的区域检查WPI，那里的数据丰富，我们可以将结果外推到更广泛的太阳系和整个宇宙。该方案的组成部分通过以下方式处理与WPI有关的物理过程：（a）通过人工刺激WPI过程进行详细的积极实验，（B）在一系列空间尺度上测量和分析自然WPI特征，（c）WPI过程的理论建模，以及（d）探索不同地球物理区域的WPI过程。

The Earth possesses a magnetic field very similar in shape to the magnetic field produced by a simple bar magnet. Magnetic field lines emerge from the planet at one magnetic pole and extend out of the atmosphere, thousands of kilometres into space, before returning to the magnetic pole in the opposite hemisphere. Rather than being a vacuum, the region of space that these field lines pass through is filled with plasma / an electrically conducting gas made up charged particles. Most of these particles originate in the Earth's atmosphere having been produced by ultraviolet sunlight which ionises gases in the high altitude atmosphere / a region known as the ionosphere. The Sun also possesses a strong magnetic field. As nuclear processes generate energy in the solar interior, the outer layer of the solar atmosphere expands outwards through the solar system forming the solar wind. When the solar wind arrives at the Earth it collides with the planet's magnetic field and is diverted around the planet. The cavity carved out of the solar wind by the Earth's magnetic field is called the magnetosphere. Inside the magnetosphere the plasma and magnetic field generally originate mainly from the Earth. Outside of the magnetosphere, they originate from the Sun. These regions are not always strictly separated and this leads to electromagnetic interactions between our planet and its nearest star. The ionosphere has a major influence on radio waves passing through it while some of the high energy particles that originate from the solar wind become trapped in radiation belts surrounding our planet at distances between 20,000-60,000 km / the part of space occupied by many Earth-orbiting satellites. At high latitudes, charged particles can escape from the radiation belts into precipitate into the upper atmosphere where they excite atmospheric gases to form the aurora borealis (i.e. the 'northern lights'). Clearly, this sun-earth connectivity not only leads to beautiful natural phenomena but also impacts upon the man-made technologies on which we depend. Approximately 99% of universe is estimated to be plasma. In this respect, the solar wind, the magnetosphere and the ionosphere are not exotic. However, plasma does not exist naturally on the surface of the Earth. Therefore, if we are to fully understand how plasma (and therefore most of the universe) behaves we need to exploit the natural plasma laboratory the surrounds our planet. Some of the biggest mysteries surround the interaction of plasmas and electromagnetic waves. For example, wave-plasma interactions (WPI) are thought to be responsible for many of the processes that cause cold plasma to be energised. These include the formation of the Earth's radiation belts or the acceleration of plasmas that cause the aurora and can damage satellites. However, the mechanisms are poorly understood. In a terrestrial setting, wave-particle interactions are frequently used as an energisation mechanism within particle accelerators. Artificially-created and confined plasmas heated by WPI lie at the heart of experimental fusion reactors that offer the hope of clean energy in the future. Clearly, an improved understanding of wave-plasma interactions is vitally important. A five-year programme of research is outlined. It's primary aim is to address this universally relevant physical process. By examining WPI in more accessible regions close to the Earth, where data are abundant, we can extrapolate results to the wider solar system and the universe as a whole. The components of the programme address the physical processes connected with WPI by means of: (a) detailed active experimentation by stimulating WPI processes artificially, (b) measurement and analysis of naturally WPI signatures at a range of spatial scales, (c) theoretical modelling of WPI processes, and (d) exploring WPI processes in different geophysical regions.