How do weak shocks accelerate high energy particles?

弱激波如何加速高能粒子？

• 批准号: ST/R003246/1
• 负责人: David Long
• 金额: $ 66.64万
• 依托单位: University College London
• 依托单位国家: 英国
• 项目类别: Fellowship
• 财政年份: 2019
• 资助国家: 英国
• 起止时间: 2019 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=ST%2FR003246%2F1
• 关键词: How; do; weak; shocks; accelerate

Shock waves are found everywhere in the Universe and are one of the most efficient ways of accelerating particles like protons and electrons. However, the conditions required to produce those shocks and accelerate particles are so extreme that they're impossible to recreate on Earth. As a result, we still don't know a lot about how these shocks accelerate particles or how they're affected by things like density or magnetic field. Most of the shocks that produce these very high energy particles are also incredibly far away in other galaxies, making them difficult to study properly. For example, while we can see a supernova shock using astronomical telescopes, it's really hard to then identify and study the particles it accelerates.However, the Earth is located close to a natural laboratory with extreme density, temperature and magnetic field variations which regularly produces large-scale shocks that shower us with energetic particles; the Sun. We have a fleet of spacecraft returning constant observations of the Sun, allowing us to see in near-real-time the sudden release of stored magnetic energy in the solar atmosphere (also called the corona). This energy release can produce bursts of radiation that we call solar flares, hurl massive bubbles of plasma called coronal mass ejections into the solar system towards the Earth and launch vast global shock waves that can travel across the Sun in under an hour. Although these shocks are so much weaker than supernovae that they shouldn't be able to accelerate any particles, they regularly produce billions of energetic particles that we can almost immediately detect at Earth. These particles can be fatal for satellites orbiting the Earth, blinding them and causing them to fail, with knock-on effects for GPS and telecommunications. With my research, I'm trying to understand why these really weak shocks occur, how they accelerate particles to incredibly high energies and how those energetic particles affect the Earth and the near-Earth environment.The Sun offers a unique opportunity to study both extreme shocks and the particles that they accelerate at the same time in unprecedented detail; we can see what happens and "touch" the resulting particles, which is something that you can't do in any other field of astrophysics. Everything about this situation is also very counterintuitive; the Sun is a pretty average star producing very weak shocks that shouldn't be able to accelerate any particles yet it manages to accelerate particles to incredibly high energies. How this happens is still an open question, and one that has implications not just for our understanding of the Sun, but also for fundamental plasma physics and space weather. If we know how this process works we might be able to predict it, which will help us to protect vulnerable spacecraft and infrastructure on Earth. On a more personal level though, working on this topic really hammers home the differences between how calm the Sun is when you look at it from the ground versus the violently active Sun producing solar eruptions which we see from space, which I just think is fascinating.

冲击波在宇宙中随处可见，是加速质子和电子等粒子的最有效方式之一。然而，产生这些冲击和加速粒子所需的条件非常极端，以至于不可能在地球上重现。因此，我们仍然不太了解这些冲击如何加速粒子或它们如何受到密度或磁场等因素的影响。大多数产生这些极高能粒子的激波在其他星系中也非常遥远，这使得它们很难正确研究。例如，虽然我们可以使用天文望远镜看到超新星冲击，但很难识别和研究它加速的粒子。然而，地球靠近一个自然实验室，具有极端的密度、温度和磁场变化，这些变化经常产生大规模的冲击给我们带来高能粒子；太阳。我们有一组航天器不断返回对太阳的观测结果，使我们能够近乎实时地看到太阳大气层（也称为日冕）中储存的磁能的突然释放。这种能量释放可以产生我们称为太阳耀斑的辐射爆发，将称为日冕物质抛射的巨大等离子体气泡抛向太阳系，向地球发射，并发射巨大的全球冲击波，可以在一小时内穿过太阳。尽管这些冲击波比超新星弱得多，因此它们不能加速任何粒子，但它们经常产生数十亿个我们几乎可以立即在地球上检测到的高能粒子。这些粒子对于绕地球运行的卫星来说可能是致命的，它们会致盲并导致卫星失效，并对 GPS 和电信产生连锁反应。通过我的研究，我试图了解为什么会发生这些非常微弱的冲击，它们如何将粒子加速到令人难以置信的高能量，以及这些高能粒子如何影响地球和近地环境。太阳提供了一个独特的机会来研究极端的冲击冲击和它们同时加速的粒子以前所未有的细节；我们可以看到发生了什么并“触摸”产生的粒子，这是天体物理学的任何其他领域都无法做到的事情。这种情况的一切也都非常违反直觉；太阳是一颗相当普通的恒星，产生的冲击波非常微弱，不应该能够加速任何粒子，但它却设法将粒子加速到令人难以置信的高能量。这是如何发生的仍然是一个悬而未决的问题，这个问题不仅对我们对太阳的理解有影响，而且对基础等离子体物理学和空间天气也有影响。如果我们知道这个过程是如何运作的，我们也许能够预测它，这将有助于我们保护地球上脆弱的航天器和基础设施。不过，从更个人的角度来看，对这个主题的研究确实让我们明白了从地面观察太阳时的平静程度与我们从太空中看到的产生太阳喷发的剧烈活跃的太阳之间的差异，我认为这很有趣。

项目成果

Observational Evidence of S-Web Source of the Slow Solar Wind

慢速太阳风 S-Web 源的观测证据

• DOI: http://dx.10.48550/arxiv.2303.12192
• 发表时间: 2023
• 作者: Baker D

Plasma Upflows Induced by Magnetic Reconnection Above an Eruptive Flux Rope

喷发通量绳上方磁重联引起的等离子体上流

• DOI: http://dx.10.1007/s11207-021-01849-7
• 发表时间: 2021
• 期刊: Solar Physics
• 影响因子: 2.8
• 作者: Baker D

Coordination within the remote sensing payload on the Solar Orbiter mission

太阳轨道飞行器任务遥感有效载荷内的协调

• DOI: http://dx.10.1051/0004-6361/201937032
• 发表时间: 2020
• 期刊: Astronomy & Astrophysics
• 影响因子: 6.5
• 作者: Auchère F

Transient Inverse-FIP Plasma Composition Evolution within a Solar Flare

太阳耀斑内瞬态逆 FIP 等离子体成分演化

• DOI: http://dx.10.3847/1538-4357/ab07c1
• 发表时间: 2019
• 期刊: The Astrophysical Journal
• 作者: Baker D

Plasma Upflows Induced by Magnetic Reconnection Above an Eruptive Flux Rope

喷发通量绳上方磁重联引起的等离子体上流

• DOI: http://dx.10.48550/arxiv.2106.16137
• 发表时间: 2021
• 作者: Baker D