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Universe
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The Multi-Scale Dynamics of Solar Wind
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The Multi-Scale Dynamics of Solar Wind

A special issue of Universe (ISSN 2218-1997). This special issue belongs to the section "Solar System".

Deadline for manuscript submissions: closed (1 December 2023) | Viewed by 3650

Special Issue Editors

Dr. Liping Yang

E-Mail Website
Guest Editor
State Key Laboratory for Space Weather, National Space Science Center, Chinese Academy of Sciences, Beijing 100190, China
Interests: solar corona; interplanetary
Dr. Jiansen He

E-Mail Website
Guest Editor
School of Earth and Space Sciences, Peking University, Beijing 100871, China
Interests: interaction of the solar wind with planets and small celestial bodies; transport of the solar wind in the heliosphere and its interaction with the intrusive interstellar medium flow; solar atmospheric heating and origin of solar wind acceleration
Prof. Dr. Xueshang Feng

E-Mail Website
Guest Editor
State Key Laboratory of Space Weather, National Space Science Center, Chinese Academy of Sciences, Beijing 100190, China
Interests: numerical simulation of the solar wind

Special Issue Information

Dear Colleagues,

Solar wind is a continuous stream of magnetic plasma that flows outward from the sun and permeates the solar system. Since it was predicted using coronal models by Parker, solar wind has been an essential topic in space physics. Now, it has been established that there are two types of solar wind. One is the fast solar wind, with speeds ranging from 500 to 800 kilometers per second, originating from coronal holes. The other is the slow-speed wind, with speeds of about 400 kilometers per second, originating from the streamer belts, coronal hole boundaries, and so on. The density, speed, and magnetic field of the solar wind can generate large weather impacts.

Additionally, solar wind is highly turbulent, exhibiting intense fluctuations ranging over several decades. Solar wind turbulence not only can heat solar wind, accelerate energetic particle, and modulate cosmic-ray propagation, but also, it is a driver of geomagnetic activity, especially at high latitudes.

This Special Issue is devoted to significant advancements in multi-scale dynamics of solar wind using space- and ground-based observations, as well as numerical simulation. We encourage submissions on data analysis and numerical simulations of solar wind, concerning its large-scale structures, its small-scale dynamics, as well as their coupling.

Dr. Liping Yang
Dr. Jiansen He
Prof. Dr. Xueshang Feng
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Universe is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • solar wind
  • turbulence
  • waves
  • MHD
  • numerical simulation

Published Papers (4 papers)

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Research

24 pages, 8562 KiB  
Article
The Changes in Multiscale Solar Wind Fluctuations on the Path from the Sun to Earth
by Igor D. Volodin, Maria O. Riazantseva, Liudmila S. Rakhmanova, Alexander A. Khokhlachev and Yuri I. Yermolaev
Universe 2024, 10(4), 186; https://doi.org/10.3390/universe10040186 - 19 Apr 2024
Viewed by 405
Abstract
This paper is devoted to the analysis of fluctuations in the solar wind plasma and interplanetary magnetic field parameters observed by Solar Orbiter and WIND spacecraft at different scales ranging from ~103 to 107 km. We consider two long data intervals [...] Read more.
This paper is devoted to the analysis of fluctuations in the solar wind plasma and interplanetary magnetic field parameters observed by Solar Orbiter and WIND spacecraft at different scales ranging from ~103 to 107 km. We consider two long data intervals where the distances between the spacecraft are 0.1 and 0.5 AU, respectively, and they are located close to the Sun–Earth line. Transformation of the fluctuation’s properties on the way from the Sun to Earth is analyzed for different types of solar wind associated with quasi-stationary and transient solar phenomena. The time series of bulk speed are shown to undergo a slight modification, even for large spacecraft separation, while the time series of the interplanetary magnetic field magnitude and components as well as proton density may be transformed even at a relatively short distance. Though the large-scale solar wind structures propagate the distance up to 0.5 AU without significant change, local structures at smaller scales may be modified. The statistical properties of the fluctuations such as relative standard deviation or probability distribution function and its moments remain nearly unchanged at different distances between the two spacecraft and are likely to depend mostly on the type of the solar wind. Full article
(This article belongs to the Special Issue The Multi-Scale Dynamics of Solar Wind)
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24 pages, 388 KiB  
Article
First Principles Description of Plasma Expansion Using the Expanding Box Model
by Sebastián Echeverría-Veas, Pablo S. Moya, Marian Lazar and Stefaan Poedts
Universe 2023, 9(10), 448; https://doi.org/10.3390/universe9100448 - 14 Oct 2023
Viewed by 1125
Abstract
Multi-scale modeling of expanding plasmas is crucial for understanding the dynamics and evolution of various astrophysical plasma systems such as the solar and stellar winds. In this context, the Expanding Box Model (EBM) provides a valuable framework to mimic plasma expansion in a [...] Read more.
Multi-scale modeling of expanding plasmas is crucial for understanding the dynamics and evolution of various astrophysical plasma systems such as the solar and stellar winds. In this context, the Expanding Box Model (EBM) provides a valuable framework to mimic plasma expansion in a non-inertial reference frame, co-moving with the expansion but in a box with a fixed volume, which is especially useful for numerical simulations. Here, fundamentally based on the Vlasov equation for magnetized plasmas and the EBM formalism for coordinates transformations, for the first time, we develop a first principles description of radially expanding plasmas in the EB frame. From this approach, we aim to fill the gap between simulations and theory at microscopic scales to model plasma expansion at the kinetic level. Our results show that expansion introduces non-trivial changes in the Vlasov equation (in the EB frame), especially affecting its conservative form through non-inertial forces purely related to the expansion. In order to test the consistency of the equations, we also provide integral moments of the modified Vlasov equation, obtaining the related expanding moments (i.e., continuity, momentum, and energy equations). Comparing our results with the literature, we obtain the same fluids equations (ideal-MHD), but starting from a first principles approach. We also obtained the tensorial form of the energy/pressure equation in the EB frame. These results show the consistency between the kinetic and MHD descriptions. Thus, the expanding Vlasov kinetic theory provides a novel framework to explore plasma physics at both micro and macroscopic scales in complex astrophysical scenarios. Full article
(This article belongs to the Special Issue The Multi-Scale Dynamics of Solar Wind)
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13 pages, 6815 KiB  
Article
Influence of Alfvén Ion–Cyclotron Waves on the Anisotropy of Solar Wind Turbulence at Ion Kinetic Scales
by Xin Wang, Linzhi Huang, Yuxin Wang and Haochen Yuan
Universe 2023, 9(9), 399; https://doi.org/10.3390/universe9090399 - 31 Aug 2023
Cited by 1 | Viewed by 806
Abstract
The power spectra of the magnetic field at ion kinetic scales have been found to be significantly influenced by Alfvén ion–cyclotron (AIC) waves. Here, we study whether and how this influence of the AIC wave depends on the θVB angle (the [...] Read more.
The power spectra of the magnetic field at ion kinetic scales have been found to be significantly influenced by Alfvén ion–cyclotron (AIC) waves. Here, we study whether and how this influence of the AIC wave depends on the θVB angle (the angle between the local mean magnetic field and the solar wind velocity direction). The wavelet technique is applied to the high time-resolution (11 vectors per second) magnetic field data from WIND spacecraft measurements in a fast solar wind stream associated with an outward magnetic sector. It is found that around the ion kinetic scales (0.52 Hz–1.21 Hz), the power spectrum in the parallel angular bin 0∘<θVB<10∘ has a slope of −4.80±0.15. When we remove the left-handed polarized AIC waves (with normalized reduced magnetic helicity smaller than −0.9) from the fluctuations, the spectral index becomes −4.09±0.11. However, the power spectrum in the perpendicular angular bin 80∘<θVB<90∘ changes very little during the wave-removal process, and its slope remains −3.22±0.07. These results indicate that the influence of the AIC waves on the magnetic spectral index at the ion kinetic scales is indeed dependent on θVB, which is due to the anisotropic distribution of the waves. Apparently, when the waves are removed from the original data, the spectral anisotropy weakens. This result may help us to better understand the physical nature of the spectral anisotropy around the ion scales. Full article
(This article belongs to the Special Issue The Multi-Scale Dynamics of Solar Wind)
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17 pages, 1792 KiB  
Article
Anisotropy of Self-Correlation Level Contours in Three-Dimensional Magnetohydrodynamic Turbulence
by Liping Yang, Jiansen He, Xin Wang, Honghong Wu, Lei Zhang and Xueshang Feng
Universe 2023, 9(9), 395; https://doi.org/10.3390/universe9090395 - 30 Aug 2023
Viewed by 804
Abstract
MHD turbulence is considered to be anisotropic owing to the presence of a magnetic field, and its self-correlation anisotropy has been unveiled by solar wind observations. Here, based on numerical results of compressible MHD turbulence with a global mean magnetic field, we explore [...] Read more.
MHD turbulence is considered to be anisotropic owing to the presence of a magnetic field, and its self-correlation anisotropy has been unveiled by solar wind observations. Here, based on numerical results of compressible MHD turbulence with a global mean magnetic field, we explore variations of the normalized self-correlation function’s (NCF) level contours with the scale as well as their evolution. The analyses reveal that the NCF’s level contours tend to elongate in the direction parallel to the mean magnetic field, and the elongation becomes weak with decreasing intervals. These results are consistent with slow solar wind observations. The less anisotropy of the NCF’s level contours with the shorter intervals can be produced by the fact that coherent structures stretch more along the parallel direction at the long intervals than at the short intervals. The analyses also disclose that as the simulation time builds up, the NCF’s level contours change thinner and thinner, and the anisotropy of the NCF’s level contours grows, which can be caused by the break of large coherent structures into small ones. The increased self-correlation anisotropy with time foretells that the self-correlation anisotropy of solar wind turbulence enlarges with the radial distance, which needs to be tested against observations by using Parker Solar Probe (PSP) measurements. Full article
(This article belongs to the Special Issue The Multi-Scale Dynamics of Solar Wind)
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