Determining the Cross-Scale Coupling whereby Magnetohydrodynamics (MHD) Solar Eruptions Produce Energetic Electrons and X-Rays

确定磁流体动力学 (MHD) 太阳喷发产生高能电子和 X 射线的跨尺度耦合

• 批准号: 1914599
• 负责人: Paul Bellan
• 金额: $ 45万
• 依托单位: California Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-07-01 至 2022-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1914599&HistoricalAwards=false
• 关键词: Determining; Cross; Scale; Coupling; whereby

Constantly-evolving, plasma-filled magnetic arches that are thousands of times bigger than the Earth cover much of the surface of the Sun. These arches sometimes suddenly erupt and eject into space a mix of plasma, magnetic field, energetic electrons/ions, X-rays, as well as copious waves. The detritus of this eruption can wreak havoc on Earth's magnetic field creating aurora, damaging spacecraft, disrupting radio communications, and in extreme circumstances, knocking out electric power grids. The large-scale evolution of the pressure, flow, magnetic fields and electric currents in these arches is described quite well by a set of equations called magnetohydrodynamics (MHD). However, MHD cannot explain why these eruptions occur nor why they generate energetic particles and X-rays because MHD does not describe the very fine-scale physics responsible for these critical phenomena. Laboratory plasmas governed by the same MHD physics as solar plasmas will be arranged to similarly evolve and erupt but in a reproducible way. The transition from large-scale MHD behavior to fine-scale non-MHD behavior producing X-rays and waves will be investigated by observing thousands of controlled eruptions using advanced diagnostics. The research project will be done by the PI assisted by a graduate student and undergraduates working as summer interns or part-time academic-year researchers. The knowledge gained from this research will advance the national health, prosperity, and secure the national defense because energetic solar particles and X-rays can damage spacecraft and harm astronauts while the disruption of Earth's magnetic field can damage electric power grids and adversely affect communications systems.This three-year research project will investigate the cross-scale coupling between MHD eruptive phenomena and fine-scale non-MHD phenomena that produce X-rays, energetic particles, and waves. The research will determine the mechanism by which the X-rays and whistler waves are generated. Preliminary evidence suggests this happens when the Rayleigh-Taylor ripples choke the jet cross-section to be of the order of the ion skin depth at which point MHD fails and a kinetic instability ensues. This kinetic instability is presumed to greatly enhance the local resistivity and thus interrupt the electric current. This current interruption is presumed to cause a large inductive voltage spike that accelerates a small fraction of the electrons to extremely high energy. Brehmsstrahlung from the collision of these fast electrons is then presumed to produce the observed X-ray burst. This working hypothesis will be tested by scanning parameters to check the presumption that the inductive voltage spike is associated with choking the current cross-section. The scaling of this mechanism to the solar corona will be investigated. While scaling of the MHD evolution is straightforward, scaling of the fine-scale non-MHD phenomena requires explaining how MHD couples to the ion depth scale in the corona. This is challenging because in the solar corona the MHD and ion skin depth scales differ by at least 100,000. The hypothesis is that coupling results from the MHD structures having a fractal character like the twisted strands of a rope being composed of still smaller twisted strands. Plasma-filled magnetic flux tubes would be like the rope strands and the finest scale strands would be of the order of the ion-skin depth. Bundles of flux ropes (strands) will be produced in the experiment and tested to see if individual strands become Rayleigh-Taylor unstable when the entire bundle is laterally accelerated. Coupling between the MHD scale (jet, kinks, Rayleigh-Taylor) and the non-MHD scale (energetic particles, X-rays, whistler waves) will be determined and used to model how solar eruptions generate energetic particles, X-rays, and waves. The research and EPO agenda of this project supports the Strategic Goals of the AGS Division in discovery, learning, diversity, and interdisciplinary research.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.

不断演化的、充满等离子体的磁拱比地球大数千倍，覆盖了太阳的大部分表面。 这些拱门有时会突然爆发，并向太空喷射出等离子体、磁场、高能电子/离子、X射线以及大量波的混合物。 这次喷发的碎屑会对地球磁场造成严重破坏，产生极光，损坏航天器，扰乱无线电通信，在极端情况下，甚至会破坏电网。 一组称为磁流体动力学 (MHD) 的方程很好地描述了这些拱形结构中压力、流量、磁场和电流的大规模演化。 然而，MHD 无法解释为什么会发生这些喷发，也无法解释它们为什么会产生高能粒子和 X 射线，因为 MHD 没有描述导致这些关键现象的非常精细的物理现象。 实验室等离子体与太阳等离子体受相同的 MHD 物理控制，将被安排以类似的方式演化和爆发，但以可重复的方式。 从大规模 MHD 行为到产生 X 射线和波的精细非 MHD 行为的转变将通过使用先进的诊断技术观察数千次受控喷发来进行研究。 该研究项目将由 PI 完成，并由一名研究生和本科生作为暑期实习生或兼职学年研究人员协助完成。 从这项研究中获得的知识将促进国民健康、繁荣和国防安全，因为高能太阳粒子和 X 射线会损坏航天器和宇航员，而地球磁场的破坏会损坏电网并对通信系统产生不利影响这个为期三年的研究项目将研究 MHD 喷发现象和产生 X 射线、高能粒子和波的细尺度非 MHD 现象之间的跨尺度耦合。 该研究将确定 X 射线和哨声波的产生机制。 初步证据表明，当瑞利-泰勒波纹将射流横截面阻塞到离子集肤深度的量级时，就会发生这种情况，此时 MHD 失效并随之发生动力学不稳定。 据推测，这种动力学不稳定性会大大增强局部电阻率，从而中断电流。 据推测，这种电流中断会导致大的感应电压尖峰，从而将一小部分电子加速到极高的能量。 据推测，这些快速电子碰撞产生的轫致辐射会产生所观察到的 X 射线爆发。 该工作假设将通过扫描参数进行测试，以检查感应电压尖峰与阻塞电流横截面相关的假设。 我们将研究这种机制在日冕上的扩展。 虽然 MHD 演化的尺度很简单，但精细尺度非 MHD 现象的尺度需要解释 MHD 如何与日冕中的离子深度尺度耦合。 这是具有挑战性的，因为在日冕中，MHD 和离子集肤深度尺度至少相差 100,000。假设是耦合是由具有分形特征的 MHD 结构产生的，就像绳子的绞合股由更小的绞合股组成一样。 等离子体填充的磁通量管就像绳索股，最细尺度的股绳将具有离子表皮深度的量级。 实验中将生产磁绳束（股）并进行测试，以查看当整个束横向加速时，各个股是否会变得瑞利-泰勒不稳定。 MHD 尺度（射流、扭结、瑞利-泰勒）和非 MHD 尺度（高能粒子、X 射线、哨声波）之间的耦合将被确定并用于模拟太阳喷发如何产生高能粒子、X 射线和波浪。 该项目的研究和 EPO 议程支持 AGS 部门在发现、学习、多样性和跨学科研究方面的战略目标。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响进行评估，被认为值得支持审查标准。

项目成果

Determination of a macro- to micro-scale progression leading to a magnetized plasma disruption

确定导致磁化等离子体破坏的宏观到微观进程

• DOI: 10.1063/1.5140348
• 发表时间: 2020
• 期刊: Physics of Plasmas
• 影响因子: 2.2
• 作者: Seo, Byonghoon;Wongwaitayakornkul, Pakorn;Haw, Magnus A.;Marshall, Ryan S.;Li, Hui;Bellan, Paul M.
• 通讯作者: Bellan, Paul M.

Magnetic Rayleigh–Taylor Instability in an Experiment Simulating a Solar Loop

模拟太阳环实验中的磁瑞利泰勒不稳定性

• DOI: 10.3847/2041-8213/ab6b2d
• 发表时间: 2020
• 期刊: The Astrophysical Journal
• 作者: Zhang, Yang;Wongwaitayakornkul, Pakorn;Bellan, Paul M.
• 通讯作者: Bellan, Paul M.

Neutral-charged-particle Collisions as the Mechanism for Accretion Disk Angular Momentum Transport

中性带电粒子碰撞作为吸积盘角动量输运的机制

• DOI: 10.3847/1538-4357/ac62d5
• 发表时间: 2022
• 期刊: The Astrophysical Journal
• 作者: Zhang, Yang;Bellan, Paul M.
• 通讯作者: Bellan, Paul M.

The electron canonical battery effect in magnetic reconnection: Completion of the electron canonical vorticity framework

磁重联中的电子正则电池效应：电子正则涡度框架的完成

• DOI: 10.1063/1.5122225
• 发表时间: 2019
• 期刊: Physics of Plasmas
• 影响因子: 2.2
• 作者: Yoon, Young Dae;Bellan, Paul M.
• 通讯作者: Bellan, Paul M.

Caltech Lab Experiments and the Insights They Provide Into Solar Corona Phenomena

• DOI: 10.1029/2020ja028139
• 发表时间: 2020-08
• 期刊: Journal of Geophysical Research: Space Physics
• 作者: P. Bellan