Special Issue "Solar and Stellar Variability and Statistical Mechanics"

A special issue of Entropy (ISSN 1099-4300).

Deadline for manuscript submissions: closed (31 May 2019).

Special Issue Editor

Dr. Eun-jin Kim
Website
Guest Editor
School of Mathematics and Statistics, University of Sheffield, Sheffield S3 7RH, UK
Interests: fluid dynamics; magnetohydrodynamics (MHD); plasma physics; self-organisation; non-equilibrium statistical mechanics; turbulence; solar/stellar physics; magnetic fusion; information theory; homeostasis in biosystems
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Special Issue Information

Dear Colleagues,

One of the most outstanding unsolved problems in classical physics is understanding solar and stellar activity and variability. Ever improving observational technologies such as high-resolution imaging data have revealed the complex, rich dynamics of solar/stellar surface phenomena on a broader range of time/length scales. Typically, the solar magnetic field varies on time scales ranging from a fraction of a second to billions of years; solar flare energy is now observed on multiple scales spanning several orders of magnitude; solar wind presents strong variability on differing time scales. Some of these phenomena (e.g. the solar cycle) are almost periodic, while others (e.g. solar flares, coronal mass ejections) are volatile and explosive. Furthermore, newly emerging data from different types of stars (e.g. Proxima) reveal similar variability and provide an excellent opportunity to test and develop statistical theory.

This Special Issue aims to present different theories of statistical mechanics to understand solar and stellar variability. Submissions addressing recent observational data and/or new theoretical development are especially welcome.

Dr. Eun-jin Kim
Guest Editor

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 papers will be 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. Entropy is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1600 CHF (Swiss Francs). 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

  • Sun, solar activity, solar cycle, solar flares, solar wind, solar coronal mass ejection, stars, stellar activity, stellar cycle, stellar flares, stellar coronae, x-rays, gamma rays, Proxima, magnetic fields, plasmas, variability, statistics, non-equilibrium, entropy, scaling analysis, power-law, waiting time, distribution, fluctuations, oscillations, self-organized criticality (SOC), probability density function (PDF)

Published Papers (2 papers)

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Research

Open AccessArticle
Thermodynamic, Non-Extensive, or Turbulent Quasi-Equilibrium for the Space Plasma Environment
Entropy 2019, 21(9), 820; https://doi.org/10.3390/e21090820 - 22 Aug 2019
Abstract
The Boltzmann–Gibbs (BG) entropy has been used in a wide variety of problems for more than a century. It is well known that BG entropy is additive and extensive, but for certain systems such as those dictated by long-range interactions, it is speculated [...] Read more.
The Boltzmann–Gibbs (BG) entropy has been used in a wide variety of problems for more than a century. It is well known that BG entropy is additive and extensive, but for certain systems such as those dictated by long-range interactions, it is speculated that the entropy must be non-additive and non-extensive. Tsallis entropy possesses these characteristics, and is parameterized by a variable q ( q = 1 being the classic BG limit), but unless q is determined from microscopic dynamics, the model remains a phenomenological tool. To this day, very few examples have emerged in which q can be computed from first principles. This paper shows that the space plasma environment, which is governed by long-range collective electromagnetic interaction, represents a perfect example for which the q parameter can be computed from microphysics. By taking the electron velocity distribution function measured in the heliospheric environment into account, and considering them to be in a quasi-equilibrium state with electrostatic turbulence known as quasi-thermal noise, it is shown that the value corresponding to q = 9 / 13 = 0 . 6923 , or alternatively q = 5 / 9 = 0 . 5556 , may be deduced. This prediction is verified against observations made by spacecraft, and it is shown to be in excellent agreement. This paper constitutes an overview of recent developments regarding the non-equilibrium statistical mechanical approach to understanding the non-extensive nature of space plasma, although some recent new developments are also discussed. Full article
(This article belongs to the Special Issue Solar and Stellar Variability and Statistical Mechanics)
Open AccessFeature PaperArticle
Magnetic Helicity and the Solar Dynamo
Entropy 2019, 21(8), 811; https://doi.org/10.3390/e21080811 - 19 Aug 2019
Abstract
Solar magnetism is believed to originate through dynamo action in the tachocline. Statistical mechanics, in turn, tells us that dynamo action is an inherent property of magnetohydrodynamic (MHD) turbulence, depending essentially on magnetic helicity. Here, we model the tachocline as a rotating, thin [...] Read more.
Solar magnetism is believed to originate through dynamo action in the tachocline. Statistical mechanics, in turn, tells us that dynamo action is an inherent property of magnetohydrodynamic (MHD) turbulence, depending essentially on magnetic helicity. Here, we model the tachocline as a rotating, thin spherical shell containing MHD turbulence. Using this model, we find an expression for the entropy and from this develop the thermodynamics of MHD turbulence. This allows us to introduce the macroscopic parameters that affect magnetic self-organization and dynamo action, parameters that include magnetic helicity, as well as tachocline thickness and turbulent energy. Full article
(This article belongs to the Special Issue Solar and Stellar Variability and Statistical Mechanics)
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