气候变化领域集成服务门户(CCPortal): Electron temperature of the solar wind

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DOI	10.1073/pnas.1917905117
	Electron temperature of the solar wind
	Boldyrev S.; Forest C.; Egedal J.
发表日期	2020
ISSN	0027-8424
起始页码	9232
结束页码	9240
卷号	117 期号:17
英文摘要	Solar wind provides an example of a weakly collisional plasma expanding from a thermal source in the presence of spatially diverging magnetic-field lines. Observations show that in the inner heliosphere, the electron temperature declines with the distance approximately as Te(r) ∼ r− 0 3 . . . r− 0 7, which is significantly slower than the adiabatic expansion law ∼r−4/3. Motivated by such observations, we propose a kinetic theory that addresses the nonadiabatic evolution of a nearly collisionless plasma expanding from a central thermal source. We concentrate on the dynamics of energetic electrons propagating along a radially diverging magnetic-flux tube. Due to conservation of their magnetic moments, the electrons form a beam collimated along the magnetic-field lines. Due to weak energy exchange with the background plasma, the beam population slowly loses its energy and heats the background plasma. We propose that no matter how weak the collisions are, at large enough distances from the source a universal regime of expansion is established where the electron temperature declines as Te(r) ∝ r− 2/5. This is close to the observed scaling of the electron temperature in the inner heliosphere. Our first-principle kinetic derivation may thus provide an explanation for the slower-than-adiabatic temperature decline in the solar wind. More broadly, it may be useful for describing magnetized collisionless winds from G-type stars. © 2020 National Academy of Sciences. All rights reserved.
英文关键词	Heliosphere; Kinetic theory; Magnetic field; Plasma; Solar wind
语种	英语
scopus关键词	adiabaticity; article; electron; energy transfer; heat; human tissue; magnetic field
来源期刊	Proceedings of the National Academy of Sciences of the United States of America
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/160297
作者单位	Boldyrev, S., Department of Physics, University of Wisconsin–Madison, Madison, WI 53706, United States, Center for Space Plasma Physics, Space Science Institute, Boulder, CO 80301, United States; Forest, C., Department of Physics, University of Wisconsin–Madison, Madison, WI 53706, United States; Egedal, J., Department of Physics, University of Wisconsin–Madison, Madison, WI 53706, United States
推荐引用方式 GB/T 7714	Boldyrev S.,Forest C.,Egedal J.. Electron temperature of the solar wind[J],2020,117(17).
APA	Boldyrev S.,Forest C.,&Egedal J..(2020).Electron temperature of the solar wind.Proceedings of the National Academy of Sciences of the United States of America,117(17).
MLA	Boldyrev S.,et al."Electron temperature of the solar wind".Proceedings of the National Academy of Sciences of the United States of America 117.17(2020).