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The Importance of Nonlinear Physics in Radiation Belt Modelling

非线性物理在辐射带建模中的重要性

基本信息

批准号：
NE/V013963/2
负责人：
Oliver Allanson
金额：
$ 50.07万
依托单位：
University of Birmingham
依托单位国家：
英国
项目类别：
Fellowship
财政年份：
2023
资助国家：
英国
起止时间：
2023 至无数据
项目状态：
未结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FV013963%2F2
关键词：
Importance Nonlinear Physics Radiation Belt

项目摘要

Space is not a vacuum, but is permeated with electrically charged particles. This fourth state of matter is called plasma, and is not familiar to us on Earth since it is created at very high temperatures. The most significant sources of plasma are stars such as our sun, with plasma both fuelling and being created by self-sustaining thermonuclear fusion. There is an ever-present 'solar wind' composed of plasma that flows out of the sun in all directions and into interstellar space at hundreds of kilometres per second. Whilst less well-known and understood to us than the first three states of matter, more than 99% of the material in the standard model of the universe is plasma. The motion of solids, liquids and gases is dominated by the familiar forces of gravity and pressure. In contrast, and due to the presence of charged particles, plasma dynamics are dominated by electric and magnetic (electromagnetic) forces. The Earth has a magnetic field similar to that of a bar magnet. This magnetic field forms a protective boundary that prevents the majority of the otherwise dangerous solar wind plasma from streaming directly towards the Earth's surface. In addition to its main function as a protective barrier, the Earth's magnetic field interacts with the plasma-filled solar wind via many complex and dynamic interactions. These different processes operate on a range of timescales from years to millionths of a second. One of the dominant global-scale processes is known as the 'Dungey Cycle'. Via the Dungey Cycle, plasma originating in the solar wind can be transported past the outermost protective barriers of the Earth's magnetic field by entering at the nightside of the Earth. Plasma originating from this, and other, mechanisms then proceeds to surround the Earth from altitudes ranging from the outer reaches of the atmosphere, up to around 60,000km on the dayside and beyond 1,000,000km on the nightside.The magnetic field and plasma surrounding the Earth are together known as a magnetosphere. As suggested above, the Earth's magnetosphere plays host to many highly energetic dynamics, and these dynamics are ultimately driven by the solar wind. Plasma sourced via the Dungey Cycle can itself be unstable, and these instabilities can generate electromagnetic waves (e.g. radio waves) that propagate throughout the magnetosphere. These radio waves can then go on to interact with other charged particles within the plasma and change their velocity. These particles can be accelerated close to the speed of light via so-called 'resonant interactions'. The regions of the Earth's magnetosphere containing these energetic particles are known as the radiation belts.Satellite technologies underpin much of our modern society: navigation, communication, defense and Earth observation. Hundreds of operational satellites orbit the Earth and must traverse the hazardous radiation environment in the radiation belts. Highly energetic particles pose many operational and financial risks to orbiting spacecraft, including total loss. These risks, and other associated ground-based effects, have led to the inclusion of Space Weather in the UK Cabinet Office National Risk Register of Civil Emergences.Recent satellite observations have revealed that electromagnetic waves can have significantly higher amplitudes (i.e. carry more energy) than previously thought. This also means that they can energise plasma particles to higer energies much more rapidly than previously thought. Numerous Space Weather forecasting models exist around the world, but none of them include these effects. The British Antarctic Survey hosts one world leading model, which is licenced to the UK Met Office. The ultimate objective of this Fellowship is to improve forecasting accuracy of this operational model by understanding and including the effects high amplitude waves have on particle dynamics. This is crucial as society becomes more and more dependent on satellite technologies.

空间不是真空，而是充满了带电粒子。物质的第四种状态被称为等离子体，我们在地球上并不熟悉，因为它是在非常高的温度下产生的。等离子体最重要的来源是像我们的太阳这样的恒星，等离子体既可以通过自我维持的热核聚变提供燃料，也可以通过自我维持的热核聚变产生。有一个永远存在的“太阳风”，由等离子体组成，以每秒数百公里的速度从太阳向各个方向流动并进入星际空间。虽然我们对物质的前三种状态不太了解，但标准宇宙模型中99%以上的物质都是等离子体。固体、液体和气体的运动受重力和压力的支配。相反，由于带电粒子的存在，等离子体动力学由电和磁（电磁）力主导。地球有一个类似于条形磁铁的磁场。这个磁场形成了一个保护性的边界，阻止了大多数危险的太阳风等离子体直接流向地球表面。除了作为保护屏障的主要功能外，地球磁场还通过许多复杂和动态的相互作用与充满等离子体的太阳风相互作用。这些不同的过程在从几年到百万分之一秒的时间尺度上运行。其中一个占主导地位的全球规模的过程被称为“邓吉循环”。通过邓吉循环，源自太阳风的等离子体可以通过进入地球的夜面而被传送通过地球磁场的最外层保护屏障。等离子体从大气层的外围开始环绕地球，在向阳面的高度可达60，000公里，在阴暗面的高度可达1，000，000公里。地球周围的磁场和等离子体一起被称为磁层。如前所述，地球的磁层承载着许多高能动力学，而这些动力学最终是由太阳风驱动的。通过邓吉循环产生的等离子体本身可能是不稳定的，这些不稳定性可以产生在整个磁层传播的电磁波（例如无线电波）。然后，这些无线电波可以继续与等离子体中的其他带电粒子相互作用，并改变它们的速度。这些粒子可以通过所谓的“共振相互作用”加速到接近光速。地球磁层中含有这些高能粒子的区域被称为辐射带。卫星技术支撑着我们现代社会的许多方面：导航、通信、国防和地球观测。数百颗运行中的卫星绕地球运行，必须穿越辐射带中的危险辐射环境。高能粒子对轨道航天器造成许多操作和财务风险，包括全部损失。这些风险以及其他相关的地面效应已导致将空间天气列入联合王国内阁办公室国家民事紧急情况风险登记册。最近的卫星观测显示，电磁波的振幅（即携带更多能量）可能比以前认为的要高得多。这也意味着它们可以比以前想象的更快地将等离子体粒子激发到更高的能量。世界各地有许多空间天气预报模型，但没有一个包括这些影响。英国南极调查局拥有一个世界领先的模型，该模型被授权给英国气象局。该奖学金的最终目标是通过理解和包括高振幅波对粒子动力学的影响来提高该业务模型的预测精度。随着社会越来越依赖卫星技术，这一点至关重要。