Linear dispersion theory of parallel electromagnetic modes for regularized Kappa-distributions

Husidic, Edin; Lazar, M.; Fichtner, H.; Scherer, K.; Astfalk, Patrick

doi:10.1063/1.5145181

Cited by 17 publications

(14 citation statements)

References 49 publications

(63 reference statements)

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“…While the detailed shape/profile of any given VDF may seem to be a nuanced issue, it is well known that instabilities can be very sensitive to deviations in the VDF away from a Maxwellian, for instance [e.g., (Goldman et al, 2007;Lazar et al, 2012;Lazar et al, 2013;Lazar et al, 2014;Lazar et al, 2017;Lazar et al, 2018;Shaaban et al, 2018;Lazar et al, 2019;Lee et al, 2019;Shaaban et al, 2019)]. Even if we ignore non-Maxwellian features, the presence of multiple Maxwellians will alter instability thresholds and our interpretation of the corresponding velocity moments [e.g., (Chen et al, 2016;Husidic et al, 2020;Verniero et al, 2020;Klein et al, 2021)]. If we cannot resolve a VDF with sufficient accuracy to elucidate these features, we will both find an apparent lack of correspondence between observations and theory.…”

mentioning

confidence: 99%

The need for accurate measurements of thermal velocity distribution functions in the solar wind

Wilson¹,

Goodrich

Turner

et al. 2022

Front. Astron. Space Sci.

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The current state of the art thermal particle measurements in the solar wind are insufficient to address many long standing, fundamental physical processes. The solar wind is a weakly collisional ionized gas experiencing collective effects due to long-range electromagnetic forces. Unlike a collisionally mediated fluid like Earth’s atmosphere, the solar wind is not in thermodynamic or thermal equilibrium. For that reason, the solar wind exhibits multiple particle populations for each particle species. We can mostly resolve the three major electron populations (e.g., core, halo, strahl, and superhalo) in the solar wind. For the ions, we can sometimes separate the proton core from a secondary proton beam and heavier ion species like alpha-particles. However, as the solar wind becomes cold or hot, our ability to separate these becomes more difficult. Instrumental limitations have prevented us from properly resolving features within each ion population. This destroys our ability to properly examine energy budgets across transient, discontinuous phenomena (e.g., shock waves) and the evolution of the velocity distribution functions. Herein we illustrate both the limitations of current instrumentation and why higher resolutions are necessary to properly address the fundamental kinetic physics of the solar wind. This is accomplished by directly comparing to some current solar wind observations with calculations of velocity moments to illustrate the inaccuracy and incompleteness of poor resolution data.

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confidence: 99%

The need for accurate measurements of thermal velocity distribution functions in the solar wind

Wilson¹,

Goodrich

Turner

et al. 2022

Front. Astron. Space Sci.

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“…Therefore, fitting the observed data with one of the above kappa recipes will not change the macroscopic behavior of the plasma and thus we have not to care about large scale fluid models (of the heliosphere), because they are all similar for the discussed distribution functions. Nevertheless, the microscopic (kinetic) behavior is affected by the choice of a recipe (Yoon et al 2019;Husidic et al 2020). Now when defining a new recipe, say, to better fit the data, it is easy with the above derived formulas to calculate the…”

Section: Discussionmentioning

confidence: 99%

“…where U(a, c, x) is the Kummer-U or Tricomi function and α is the cutoff-parameter, which reproduces the SKD for α = 0. The characteristics and physical implications of the RKD are still expolored, e.g., regarding the pressure and heat flux (Lazar et al 2019) or the dispersion properties (Husidic et al 2020) in RKD-plasmas. In literature we do find not only the standard/regularized κ-distributions, but also some extensions.…”

Section: Introductionmentioning

confidence: 99%

The κ-cookbook: a novel generalizing approach to unify κ-like distributions for plasma particle modelling

Scherer

Husidic

Lazar

et al. 2020

Monthly Notices of the Royal Astronomical Society

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Abstract In the literature different so-called κ-distribution functions are discussed to fit and model the velocity (or energy) distributions of solar wind species, pickup ions or magnetospheric particles. Here we introduce a generalized (isotropic) κ-distribution as a ”cookbook”, which admits as special cases, or ”recipes”, all the other known versions of κ-models. A detailed analysis of the generalized distribution function is performed, providing general analytical expressions for the velocity moments, Debye length, and entropy, and pointing out a series of general requirements that plasma distribution functions should satisfy. From a contrasting analysis of the recipes found in the literature, we show that all of them lead to almost the same macroscopic parameters with a small standard deviation between them. However, one of these recipes called the regularized κ-distribution provides a functional alternative for macroscopic parameterization without any constraint for the power-law exponent κ.

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“…Modern numerical tools such as LEOPARD (Astfalk and Jenko, 2017) and ALPS exist that are capable of this evaluation; however, a systematic application to measured electron distributions is still outstanding (for notable exceptions, see Husidic et al, 2020;Page et al, 2021;Schroeder et al, 2021). 6.…”

Section: Conclusion and Open Questionsmentioning

confidence: 99%

Electron-Driven Instabilities in the Solar Wind

Verscharen

Chandran²,

Boella³

et al. 2022

Front. Astron. Space Sci.

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The electrons are an essential particle species in the solar wind. They often exhibit non-equilibrium features in their velocity distribution function. These include temperature anisotropies, tails (kurtosis), and reflectional asymmetries (skewness), which contribute a significant heat flux to the solar wind. If these non-equilibrium features are sufficiently strong, they drive kinetic micro-instabilities. We develop a semi-graphical framework based on the equations of quasi-linear theory to describe electron-driven instabilities in the solar wind. We apply our framework to resonant instabilities driven by temperature anisotropies. These include the electron whistler anisotropy instability and the propagating electron firehose instability. We then describe resonant instabilities driven by reflectional asymmetries in the electron distribution function. These include the electron/ion-acoustic, kinetic Alfvén heat-flux, Langmuir, electron-beam, electron/ion-cyclotron, electron/electron-acoustic, whistler heat-flux, oblique fast-magnetosonic/whistler, lower-hybrid fan, and electron-deficit whistler instability. We briefly comment on non-resonant instabilities driven by electron temperature anisotropies such as the mirror-mode and the non-propagating firehose instability. We conclude our review with a list of open research topics in the field of electron-driven instabilities in the solar wind.

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Linear dispersion theory of parallel electromagnetic modes for regularized Kappa-distributions

Cited by 17 publications

References 49 publications

The need for accurate measurements of thermal velocity distribution functions in the solar wind

The need for accurate measurements of thermal velocity distribution functions in the solar wind

The κ-cookbook: a novel generalizing approach to unify κ-like distributions for plasma particle modelling

Electron-Driven Instabilities in the Solar Wind

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