Generation of high energy particles in solar flares - towards realistic models

太阳耀斑中高能粒子的产生 - 走向现实模型

• 批准号: ST/I000828/1
• 负责人: Philippa Browning
• 金额: $ 47.47万
• 依托单位: University of Manchester
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2011
• 资助国家: 英国
• 起止时间: 2011 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=ST%2FI000828%2F1
• 关键词: Generation; energy; particles; solar; flares

Solar flares are dramatic and complex events, which give off electromagnetic radiation in almost all wavelength bands across the spectrum, and also directly emit high energy particles into space. They are of great interest both in their own right and because of their significant effects on the Earth's space environment through 'space weather'. The high energy particles and electromagnetic radiation from flares can damage satellites as well as power systems on the Earth, and are potentially extremely hazardous to astronauts. Flares were first observed in white light during the 19th century by Carrington - who noticed strong geomagnetic activity and speculated that there might be some connection with magnetic fields. But real progress in understanding the nature and origin of flares came in the space age, particularly with the advent of observations in X-rays from space-borne telescopes. It is now well-established that the primary energy release mechanism is the process of magnetic reconnection, whereby oppositely-directed fieldlines are pushed together causing the efficient dissipation of stored magnetic energy. Magnetic reconnection occurs in a 'current sheet' - a region of strong variation in magnetic field - which is the site of the energy release. However, there are major outstanding issues concerning solar flares to be resolved: in particular, the origin of the large numbers of high energy (non-thermal) charged particles - both ions and electrons. Whilst much new light has been shed on the properties of these particles by recent observations, especially from the Hard X-ray imaging telescope RHESSI, these new observations have posed new challenges to theory and modelling. One very powerful approach to understanding the origin of high energy particles in flare is to calculate the trajectories of 'test particles' - individual protons and electrons - in background electromagnetic fields corresponding to some model of magnetic reconnection. This has been widely used for simple two-dimensional, steady magnetic and electric fields. We propose to develop such models so that they are much more realistic and representative of the actual situation in solar flares. Firstly, we will consider how effects such as collisions with other particles, and emission of radiation, affects the motion of the charged particles and how they gain energy. Secondly, we will consider much more complex and realistic models of the background electromagnetic fields, which are three-dimensional and time-dependent. This will incorporate the effects of turbulence, and we will explore whether fragmentation of the reconnecting current sheet can explain the acceleration of the large numbers of protons and electrons which are observed in flares. Finally, we will start to develop sophisticated self-consistent models which incorporate the effects of the accelerated charged particles on the electromagnetic fields. The outcomes of our theoretical models will be compared with observations of hard X-rays from RHESSI as well as radio and mm-waves from the new instruments LoFAR (Low Frequency Radio ARray) and the forthcoming ALMA (Atacama LArge Millimetre Array).

太阳耀斑是戏剧性且复杂的事件，它在整个光谱上几乎所有波长带中散发电磁辐射，并且还直接将高能量颗粒散发到太空中。它们本身都引起了人们的极大兴趣，并且由于它们通过“太空天气”对地球太空环境产生了重大影响。耀斑的高能量颗粒和电磁辐射会损坏卫星以及地球上的动力系统，并且可能对宇航员极为危险。卡灵顿（Carrington）在19世纪首先在白光下观察到耀斑 - 他注意到强大的地磁活动，并推测可能与磁场有一定的联系。但是，了解耀斑的性质和起源的真正进步是在太空时代的出现，尤其是随着太空传播望远镜的X射线观察的出现。现在已经良好的是，主要的能量释放机制是磁重新连接的过程，从而将相对指导的现场线推在一起，从而导致储存的磁能有效耗散。磁重新连接发生在“电流” - 磁场中强烈变化的区域 - 这是能量释放的位置。但是，关于太阳火焰要解决的主要问题：特别是，高能（非热）带电颗粒的起源 - 离子和电子。尽管最近的观察结果尤其是从硬X射线成像望远镜Rhessi来看，尽管这些粒子的特性已经散发出许多新的光，但这些新观察结果对理论和建模构成了新的挑战。一种非常有力的方法来理解耀斑中高能量颗粒的起源是计算背景电磁场中“测试颗粒”（单个质子和电子）的轨迹，与某些磁性重新连接相对应。这已被广泛用于简单的二维，稳定的磁场和电场。我们建议开发这样的模型，以使它们更现实，并代表太阳耀斑的实际情况。首先，我们将考虑与其他颗粒发生碰撞以及辐射的发射等效果如何影响带电颗粒的运动以及它们如何获得能量。其次，我们将考虑背景电磁场的更复杂和现实的模型，这些模型是三维且依赖时间的。这将结合湍流的影响，我们将探讨重新连接电流纸的碎片是否可以解释大量质子和电子的加速度，这些质子和电子在耀斑中观察到。最后，我们将开始开发复杂的自洽模型，这些模型结合了加速带电颗粒对电磁场的影响。我们的理论模型的结果将与Rhessi的硬X射线以及新工具Lofar（低频无线电阵列）和即将到来的Alma（Atacama大毫米阵列）的无线电和MM波的观察进行比较。

项目成果

Magnetic Relaxation and Particle Acceleration in a Flaring Twisted Coronal Loop

• DOI: 10.1007/s11207-011-9900-9
• 发表时间: 2012-04
• 期刊: Solar Physics
• 影响因子: 2.8
• 作者: M. Gordovskyy;P. Browning

Coronal heating by the partial relaxation of twisted loops

• DOI: 10.1051/0004-6361/201219725
• 发表时间: 2013-02-01
• 期刊: ASTRONOMY & ASTROPHYSICS
• 影响因子: 6.5
• 作者: Bareford, M. R.;Hood, A. W.;Browning, P. K.
• 通讯作者: Browning, P. K.

Plasma motions and non-thermal line broadening in flaring twisted coronal loops

• DOI: 10.1051/0004-6361/201527249
• 发表时间: 2015-08
• 期刊: arXiv: Solar and Stellar Astrophysics
• 作者: M. Gordovskyy;E. P. Kontar;P. Browning

Two-fluid and magnetohydrodynamic modelling of magnetic reconnection in the MAST spherical tokamak and the solar corona

• DOI: 10.1088/0741-3335/58/1/014041
• 发表时间: 2015-07
• 期刊: Plasma Physics and Controlled Fusion
• 影响因子: 2.2
• 作者: P. Browning;S. Cardnell;M. Evans;F. Arese Lucini;V. Lukin;K. McClements;A. Stanier

Effect of Collisions and Magnetic Convergence on Electron Acceleration and Transport in Reconnecting Twisted Solar Flare Loops

• DOI: 10.1007/s11207-012-0124-4
• 发表时间: 2013-06
• 期刊: Solar Physics
• 影响因子: 2.8
• 作者: M. Gordovskyy;P. Browning;E. P. Kontar;N. Bian