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.

太阳风是热颗粒的流动，主要是电子和离子，以每小时数百万英里的速度从太阳流出。随着太阳风的膨胀，预计会冷却。但是，在距离太阳的大距离处，太阳风不如简单的热力学定律所期望的那么冷。目前尚不清楚太阳风的加热是什么，因为加热通常需要颗粒之间的频繁碰撞，而太阳风几乎无碰撞。在其他天体物理和实验室系统中会出现类似的问题。该项目将开发一种有效的方法来描述无碰撞等离子体中的加热和热传导。它将利用一种特殊的对称性，自相似性，在扩展天然和实验室等离子体中经常观察到。该研究项目的结果也将有助于改善太空天气建模中的最新技术，在该模型中，太阳风的准确表示对于正确传播太阳能对地球磁层的影响很重要。电子热传导的问题对于理解天然和实验室等离子体的能量传输至关重要。它的一般分析解决方案尚不清楚，除了spitzer Harm Case，当电子平均自由路径明显短于温度梯度的尺度时。许多天然等离子体，例如太阳能电晕和太阳风，簇内培养基都是弱碰撞的，因此不满足上述条件。将开发出一种新颖的方法，该方法考虑到这样一个事实，即这种系统中的物理参数（例如温度，密度和磁场）通常会随着距离热源的距离的力量而下降。这使人们可以找到完整动力学方程的自相似解，并以非扰动方式构建电子分布函数。

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