Special Issue "A Themed Issue in Honor of Professor Reinhard Schlickeiser on the Occasion of His 70th Birthday"

A special issue of Physics (ISSN 2624-8174). This special issue belongs to the section "Statistical Physics and Nonlinear Phenomena".

Deadline for manuscript submissions: closed (31 October 2021).

Special Issue Editors

Prof. Dr. Martin Pohl
E-Mail Website
Guest Editor
1. Theoretical Astroparticle Physics, DESY, Platanenallee 6, 15738 Zeuthen, Germany
2. Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Strasse 24/25, 14476 Potsdam, German
Interests: particle acceleration in space; wave-particle interactions; gamma-ray astrophysics
Prof. Dr. Peter Yoon
E-Mail Website
Guest Editor
Institute of Physical Science and Technology, University of Maryland, College Park, MD 20742, USA
Interests: fundamental and theoretical plasma physics; nonlinear plasma physics; Kinetic theory of plasmas and ionized gas; space plasma physics; magnetospheric and heliospheric physics
Dr. Horst Fichtner
E-Mail Website
Guest Editor
Institute of Theoretical Physics IV: Plasma-Astroparticle Physics, Ruhr University Bochum, 44780 Bochum, Germany
Interests: space physics; astrophysics; plasma physics

Special Issue Information

Dear colleagues,

This Special Issue is dedicated to Professor Reinhard Schlickeiser on the occasion of his 70th birthday. Reinhard Schlickeiser’s internationally well-recognized work, comprising several hundred research articles and the comprehensive monograph “Cosmic Ray Astrophysics,” has a lasting influence in several areas of astrophysics. He has also inspired a large number of junior researchers, many of whom now pursue a successful academic career. Over the decades, he has motivated and established many fruitful collaborations that triggered new ideas and provided new insights into various plasma- and astrophysical topics.

The Special Issue aims at presenting original papers by Reinhard Schlickeiser’s collaborators that document the breadth of his scientific accomplishments and the subsequent studies that he directly or indirectly influenced as collaborator or as a teacher. This Special Issue may serve as an inspiration to others to follow in his path and to accept the challenges waiting in the many areas of astrophysics that were Reinhard’s turf.

Prof. Dr. Martin Pohl
Prof. Dr. Peter Yoon
Dr. Horst Fichtner
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 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. Physics is an international peer-reviewed open access quarterly 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 1200 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

  • astrophysics
  • plasma astrophysics
  • space physics
  • cosmic rays
  • transport theory of energetic particles
  • gamma rays
  • plasma physics
  • plasma waves
  • instabilities

Published Papers (7 papers)

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Editorial

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Editorial
Personal Reminiscences of Reinhard Schlickeiser
Physics 2021, 3(4), 1051-1053; https://0-doi-org.brum.beds.ac.uk/10.3390/physics3040066 - 12 Nov 2021
Viewed by 207
Abstract
In 1979, I arrived back at the University of Chicago from a two-year stint in Australia to find a very large German post-doc eagerly awaiting me, so we could work together on transport of cosmic ray electrons perpendicular to the galactic plane [...] [...] Read more.
In 1979, I arrived back at the University of Chicago from a two-year stint in Australia to find a very large German post-doc eagerly awaiting me, so we could work together on transport of cosmic ray electrons perpendicular to the galactic plane [...] Full article

Research

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Article
Proton-Alpha Drift Instability of Electromagnetic Ion-Cyclotron Modes: Quasilinear Development
Physics 2021, 3(4), 1175-1189; https://0-doi-org.brum.beds.ac.uk/10.3390/physics3040075 (registering DOI) - 01 Dec 2021
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Abstract
The ability of space plasmas to self-regulate through mechanisms involving self-generated fluctuations is a topic of high interest. This paper presents the results of a new advanced quasilinear (QL) approach for the instability of electromagnetic ion-cyclotron modes driven by the relative alpha-proton drift [...] Read more.
The ability of space plasmas to self-regulate through mechanisms involving self-generated fluctuations is a topic of high interest. This paper presents the results of a new advanced quasilinear (QL) approach for the instability of electromagnetic ion-cyclotron modes driven by the relative alpha-proton drift observed in solar wind. For an extended parametric analysis, the present QL approach includes also the effects of intrinsic anisotropic temperatures of these populations. The enhanced fluctuations contribute to an exchange of energy between proton and alpha particles, leading to important variations of the anisotropies, the proton-alpha drift and the temperature contrast. The results presented here can help understand the observational data, in particular, those revealing the local variations associated with the properties of protons and alpha particles as well as the spatial profiles in the expanding solar wind. Full article
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Article
A Shock-in-Jet Synchrotron Mirror Model for Blazars
Physics 2021, 3(4), 1112-1122; https://0-doi-org.brum.beds.ac.uk/10.3390/physics3040070 - 22 Nov 2021
Viewed by 183
Abstract
Reinhard Schlickeiser has made groundbreaking contributions to various aspects of blazar physics, including diffusive shock acceleration, the theory of synchrotron radiation, the production of gamma-rays through Compton scattering in various astrophysical sources, etc. This paper, describing the development of a self-consistent shock-in-jet model [...] Read more.
Reinhard Schlickeiser has made groundbreaking contributions to various aspects of blazar physics, including diffusive shock acceleration, the theory of synchrotron radiation, the production of gamma-rays through Compton scattering in various astrophysical sources, etc. This paper, describing the development of a self-consistent shock-in-jet model for blazars with a synchrotron mirror feature, is therefore an appropriate contribution to a Special Issue in honor of Reinhard Schlickeiser’s 70th birthday. The model is based on our previous development of a self-consistent shock-in-jet model with relativistic thermal and non-thermal particle distributions evaluated via Monte-Carlo simulations of diffusive shock acceleration, and time-dependent radiative transport. This model has been very successful in modeling spectral variability patterns of several blazars, but has difficulties describing orphan flares, i.e., high-energy flares without a significant counterpart in the low-frequency (synchrotron) radiation component. As a solution, this paper investigates the possibility of a synchrotron mirror component within the shock-in-jet model. It is demonstrated that orphan flares result naturally in this scenario. The model’s applicability to a recently observed orphan gamma-ray flare in the blazar 3C279 is discussed and it is found that only orphan flares with mild (≲ a factor of 2–3) enhancements of the Compton dominance can be reproduced in a synchrotron-mirror scenario, if no additional parameter changes are invoked. Full article
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Article
Studying the Influence of External Photon Fields on Blazar Spectra Using a One-Zone Hadro-Leptonic Time-Dependent Model
Physics 2021, 3(4), 1098-1111; https://0-doi-org.brum.beds.ac.uk/10.3390/physics3040069 - 18 Nov 2021
Viewed by 180
Abstract
The recent associations of neutrinos with blazars require the efficient interaction of relativistic protons with ambient soft photon fields. However, along side the neutrinos, γ-ray photons are produced, which interact with the same soft photon fields producing electron-positron pairs. The strength of [...] Read more.
The recent associations of neutrinos with blazars require the efficient interaction of relativistic protons with ambient soft photon fields. However, along side the neutrinos, γ-ray photons are produced, which interact with the same soft photon fields producing electron-positron pairs. The strength of this cascade has significant consequences on the photon spectrum in various energy bands and puts severe constraints on the pion and neutrino production. In this study, we discuss the influence of the external thermal photon fields (accretion disk, broad-line region, and dusty torus) on the proton-photon interactions, employing a newly developed time-dependent one-zone hadro-leptonic code OneHaLe. We present steady-state cases, as well as a time-dependent case, where the emission region moves through the jet. Within the limits of this toy study, the external fields can disrupt the “usual” double-humped blazar spectrum. Similarly, a moving region would cross significant portions of the jet without reaching the previously-found steady states. Full article
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Article
Cylindrical and Spherical Nucleus-Acoustic Solitary and Shock Waves in Degenerate Electron-Nucleus Plasmas
Physics 2021, 3(4), 1088-1097; https://0-doi-org.brum.beds.ac.uk/10.3390/physics3040068 - 16 Nov 2021
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Abstract
The basic characteristics of cylindrical as well as spherical solitary and shock waves in degenerate electron-nucleus plasmas are theoretically investigated. The electron species is assumed to be cold, ultra-relativistically degenerate, negatively charged gas, whereas the nucleus species is considered a cold, non-degenerate, positively [...] Read more.
The basic characteristics of cylindrical as well as spherical solitary and shock waves in degenerate electron-nucleus plasmas are theoretically investigated. The electron species is assumed to be cold, ultra-relativistically degenerate, negatively charged gas, whereas the nucleus species is considered a cold, non-degenerate, positively charged, viscous fluid. The reductive perturbation technique is utilized in order to reduce the basic equations (governing the degenerate electron-nucleus plasmas under consideration) to the modified Korteweg-de Vries and Burgers equations. The latter are numerically solved and analyzed to detect the basic characteristics of solitary and shock waves in such electron-nucleus plasmas. The nonlinear nucleus-acoustic waves are found to be propagated in the form of solitary as well as shock waves in such degenerate electron-nucleus plasmas. Their basic properties as well as their time evolution are significantly modified by the effects of cylindrical as well as spherical geometries. The results of this study is expected to be applicable not only to astrophysical compact objects, but also to ultra-cold dense plasmas produced in laboratory. Full article
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Article
Landau Damping of Langmuir Waves: An Alternative Derivation
Physics 2021, 3(4), 940-954; https://0-doi-org.brum.beds.ac.uk/10.3390/physics3040059 - 29 Oct 2021
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Abstract
In this paper, a discussion of the Landau damping of Langmuir waves is presented together with a simple derivation which does not require the application of methods of complex analysis. A general dispersion relation is derived systematically which corresponds to a nonlinear equation. [...] Read more.
In this paper, a discussion of the Landau damping of Langmuir waves is presented together with a simple derivation which does not require the application of methods of complex analysis. A general dispersion relation is derived systematically which corresponds to a nonlinear equation. The latter equation is solved numerically but asymptotic limits are also discussed. Full article
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Other

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Brief Report
Plasma Flows in Solar Filaments as Electromagnetically Driven Vortical Flows
Physics 2021, 3(4), 1046-1050; https://0-doi-org.brum.beds.ac.uk/10.3390/physics3040065 - 10 Nov 2021
Viewed by 214
Abstract
Electromagnetic expulsion acts on a body suspended in a conducting fluid or plasma, which is subject to the influence of electric and magnetic fields. Physically, the effect is a magnetohydrodynamic analogue of the buoyancy (Archimedean) force, which is caused by the nonequal electric [...] Read more.
Electromagnetic expulsion acts on a body suspended in a conducting fluid or plasma, which is subject to the influence of electric and magnetic fields. Physically, the effect is a magnetohydrodynamic analogue of the buoyancy (Archimedean) force, which is caused by the nonequal electric conductivities inside and outside the body. It is suggested that electromagnetic expulsion can drive the observed plasma counter-streaming flows in solar filaments. Exact analytical solutions and scaling arguments for a characteristic plasma flow speed are reviewed, and their applicability in the limit of large magnetic Reynolds numbers, relevant in the solar corona, is discussed. Full article
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