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Self-Similar Theory of Electron Thermal Conduction in a Weakly Collisional Plasma

弱碰撞等离子体中电子热传导的自相似理论

基本信息

批准号：
1707272
负责人：
Stanislav Boldyrev
金额：
$ 30万
依托单位：
University of Wisconsin-Madison
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2017
资助国家：
美国
起止时间：
2017-08-15 至 2021-07-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1707272&HistoricalAwards=false
关键词：
Self Similar Theory Electron Thermal

项目摘要

The solar wind is a flow of hot particles, mostly electrons and ions, streaming from the Sun with the speed of millions of miles per hour. As the solar wind expands, it is expected to cool. However, at large distances from the Sun, the solar wind turns out to be not as cold as one would expect from the simple laws of thermodynamics. It is currently not well understood what heats the solar wind, since heating generally requires frequent collisions between the particles and the solar wind is nearly collisionless. A similar problem arises in other astrophysical and laboratory systems. This project will develop an efficient method for describing heating and heat conduction in collisionless plasmas. It will utilize a special symmetry, self-similarity, often observed in expanding natural and laboratory plasmas. The outcomes of this research project will also be instrumental to improving the state of the art in space weather modeling, where accurate representations of the solar wind are important for correctly propagating the impacts of the solar activity on the Earth's magnetosphere. The problem of electron heat conduction is central for understanding energy transport in natural and laboratory plasmas. Its general analytical solution is unknown, except for the Spitzer-Harm case when the electron mean free path is significantly shorter than the scale of a temperature gradient. Many natural plasmas, e.g., solar corona and solar wind, intracluster medium, are weakly collisional, where the above condition is not satisfied. A novel approach will be developed, which takes into account the fact that the physical parameters such as temperature, density, and magnetic field in such systems often decline as powers of the distance from the heat source. This allows one to find self-similar solutions of the full kinetic equation, and to construct the electron distribution function in a non-perturbative fashion.

太阳风是一种热粒子流，主要是电子和离子，以每小时数百万英里的速度从太阳中流出。随着太阳风的膨胀，它预计会冷却。然而，在距离太阳很远的地方，太阳风并不像人们从热力学简单定律中所期望的那样冷。目前还不清楚是什么加热了太阳风，因为加热通常需要粒子之间的频繁碰撞，而太阳风几乎是无碰撞的。在其他天体物理学和实验室系统中也出现了类似的问题。本计画将发展一种有效的方法来描述无碰撞电浆中的加热与热传导。它将利用一种特殊的对称性，即自相似性，这在自然和实验室等离子体膨胀中经常观察到。这一研究项目的成果还将有助于提高空间气象建模的最新水平，因为准确表示太阳风对于正确传播太阳活动对地球磁层的影响至关重要。电子热传导问题是理解自然和实验室等离子体中能量传输的核心。它的一般解析解是未知的，除了Spitzer-Harm的情况下，当电子的平均自由程是显着短于温度梯度的规模。许多天然等离子体，例如，日冕和太阳风是弱碰撞的团内介质，不满足上述条件。将开发一种新的方法，它考虑到这样的事实，即物理参数，如温度，密度和磁场在这样的系统中往往下降的功率的距离热源。这使得人们能够找到完整动力学方程的自相似解，并以非微扰的方式构造电子分布函数。

项目成果

期刊论文数量（10）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Kinetic theory of the electron strahl in the solar wind

太阳风中电子斯特拉尔的动力学理论

DOI：
10.1093/mnras/stz2378
发表时间：
2019
期刊：
Monthly Notices of the Royal Astronomical Society
影响因子：
4.8
作者：
Boldyrev, Stanislav;Horaites, Konstantinos
通讯作者：
Horaites, Konstantinos

Electron temperature of the solar wind

DOI：
10.1073/pnas.1917905117
发表时间：
2020-04-28
期刊：
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
影响因子：
11.1
作者：
Boldyrev, Stanislav;Forest, Cary;Egedal, Jan
通讯作者：
Egedal, Jan

Stability analysis of core–strahl electron distributions in the solar wind

太阳风中核心斯特拉尔电子分布的稳定性分析