Special Issue "Dynamical Processes in Space Plasmas"

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Applied Physics".

Deadline for manuscript submissions: closed (30 October 2021) | Viewed by 2609

Special Issue Editor

Dr. Georgios Nicolaou
E-Mail Website
Guest Editor
Department of Space and Climate Physics, Mullard Space Science Laboratory, University College London, London, Dorking, Surrey RH5 6NT, UK
Interests: space plasma physics; solar wind; planetary science; space plasma instrumentation; plasma simulation; plasma and fluid thermodynamics

Special Issue Information

Dear Colleagues,

Space plasma studies are crucial in understanding numerous physical, multiscale processes in nature. The scientific analysis of in situ and remote sensing observations, in combination with the development of theories and models, sheds light on mechanisms governing plasmas within several space regimes. Space plasmas are essentially collisionless systems, and the velocity distribution functions of the plasma particles often exhibit features that are out of the classic thermal equilibrium, which play a vital role in the dynamics of the system. The detailed characterisation of such plasma populations brings closure to important science questions, such as addressing the sources of plasma heating and acceleration.

For this Special Issue, we invite the submissions of original papers and reviews of scientific papers investigating dynamical processes in collisionless space plasmas. The submitted papers should provide new knowledge regarding physical properties, the accurate description and analysis of plasma populations in specific plasma regimes or structures. Purely theoretical studies or purely modelling papers that cover new aspects and original concepts of space plasma processes are strongly encouraged. Also welcomed are papers presenting new methods and analysis tools for the analysis of plasma observations. Should you have any queries, please contact me by e-mail.

Dr. Georgios Nicolaou
Guest Editor

Manuscript Submission Information

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Keywords

  • Collisionless plasmas
  • Space plasmas
  • Plasma dynamics

Published Papers (3 papers)

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Research

Article
Significance of Bernoulli Integral Terms for the Solar Wind Protons at 1 au
Appl. Sci. 2021, 11(10), 4643; https://doi.org/10.3390/app11104643 - 19 May 2021
Cited by 1 | Viewed by 634
Abstract
The Bernoulli integral describes the energy conservation of a fluid along specific streamlines. The integral is the sum of individual terms that contain the plasma density, speed, temperature, and magnetic field. Typical solar wind analyses use the fluctuations of the Bernoulli integral as [...] Read more.
The Bernoulli integral describes the energy conservation of a fluid along specific streamlines. The integral is the sum of individual terms that contain the plasma density, speed, temperature, and magnetic field. Typical solar wind analyses use the fluctuations of the Bernoulli integral as a criterion to identify different plasma streamlines from single spacecraft observations. However, the accurate calculation of the Bernoulli integral requires accurately determining the plasma polytropic index from the analysis of density and temperature observations. To avoid this complexity, we can simplify the calculations by keeping only the dominant terms of the integral. Here, we analyze proton plasma and magnetic field observations obtained by the Wind spacecraft at 1 au, during 1995. We calculate the Bernoulli integral terms and quantify their significance by comparing them with each other. We discuss potential simplifications of the calculations in the context of determining solar wind proton thermodynamics using single spacecraft observations. Full article
(This article belongs to the Special Issue Dynamical Processes in Space Plasmas)
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Article
Estimating the Polytropic Indices of Plasmas with Partial Temperature Tensor Measurements: Application to Solar Wind Protons at ~1 au
Appl. Sci. 2021, 11(9), 4019; https://doi.org/10.3390/app11094019 - 28 Apr 2021
Viewed by 597
Abstract
We examine the relationships between temperature tensor elements and their connection to the polytropic equation, which describes the relationship between the plasma scalar temperature and density. We investigate the possibility to determine the plasma polytropic index by fitting the fluctuations of temperature either [...] Read more.
We examine the relationships between temperature tensor elements and their connection to the polytropic equation, which describes the relationship between the plasma scalar temperature and density. We investigate the possibility to determine the plasma polytropic index by fitting the fluctuations of temperature either perpendicular or parallel to the magnetic field. Such an application is particularly useful when the full temperature tensor is not available from the observations. We use solar wind proton observations at ~1 au to calculate the correlations between the temperature tensor elements and the scalar temperature. Our analysis also derives the polytropic equation in selected streamlines of solar wind plasma proton observations that exhibit temperature anisotropies related to stream-interaction regions. We compare the polytropic indices derived by fitting fluctuations of the scalar, perpendicular, and parallel temperatures, respectively. We show that the use of the parallel or perpendicular temperature, instead of the scalar temperature, still accurately derives the true, average polytropic index value, but only for a certain level of temperature anisotropy variability within the analyzed streamlines. The use of the perpendicular temperature leads to more accurate calculations, because its correlation with the scalar temperature is less affected by the anisotropy fluctuations. Full article
(This article belongs to the Special Issue Dynamical Processes in Space Plasmas)
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Article
Design and Optimization of a High-Time-Resolution Magnetic Plasma Analyzer (MPA)
Appl. Sci. 2020, 10(23), 8483; https://doi.org/10.3390/app10238483 - 27 Nov 2020
Cited by 3 | Viewed by 918
Abstract
In-situ measurements of space plasma throughout the solar system require high time resolution to understand the plasma’s kinetic fine structure and evolution. In this context, research is conducted to design instruments with the capability to acquire the plasma velocity distribution and its moments [...] Read more.
In-situ measurements of space plasma throughout the solar system require high time resolution to understand the plasma’s kinetic fine structure and evolution. In this context, research is conducted to design instruments with the capability to acquire the plasma velocity distribution and its moments with high cadence. We study a new instrument design, using a constant magnetic field generated by two permanent magnets, to analyze solar wind protons and α-particles with high time resolution. We determine the optimal configuration of the instrument in terms of aperture size, sensor position, pixel size and magnetic field strength. We conduct this analysis based on analytical calculations and SIMION simulations of the particle trajectories in our instrument. We evaluate the velocity resolution of the instrument as well as Poisson errors associated with finite counting statistics. Our instrument is able to resolve Maxwellian and κ-distributions for both protons and α-particles. This method retrieves measurements of the moments (density, bulk speed and temperature) with a relative error below 1%. Our instrument design achieves these results with an acquisition time of only 5 ms, significantly faster than state-of-the-art electrostatic analyzers. Although the instrument only acquires one-dimensional cuts of the distribution function in velocity space, the simplicity and reliability of the presented instrument concept are two key advantages of our new design. Full article
(This article belongs to the Special Issue Dynamical Processes in Space Plasmas)
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