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Open AccessArticle

On the Determination of Kappa Distribution Functions from Space Plasma Observations

Department of Space and Climate Physics, Mullard Space Science Laboratory, University College London, Dorking, Surrey RH5 6NT, UK
Southwest Research Institute, San Antonio, TX 78238, USA
Author to whom correspondence should be addressed.
Entropy 2020, 22(2), 212;
Received: 24 January 2020 / Revised: 9 February 2020 / Accepted: 10 February 2020 / Published: 13 February 2020
(This article belongs to the Special Issue Theoretical Aspects of Kappa Distributions)
The velocities of space plasma particles, often follow kappa distribution functions. The kappa index, which labels and governs these distributions, is an important parameter in understanding the plasma dynamics. Space science missions often carry plasma instruments on board which observe the plasma particles and construct their velocity distribution functions. A proper analysis of the velocity distribution functions derives the plasma bulk parameters, such as the plasma density, speed, temperature, and kappa index. Commonly, the plasma bulk density, velocity, and temperature are determined from the velocity moments of the observed distribution function. Interestingly, recent studies demonstrated the calculation of the kappa index from the speed (kinetic energy) moments of the distribution function. Such a novel calculation could be very useful in future analyses and applications. This study examines the accuracy of the specific method using synthetic plasma proton observations by a typical electrostatic analyzer. We analyze the modeled observations in order to derive the plasma bulk parameters, which we compare with the parameters we used to model the observations in the first place. Through this comparison, we quantify the systematic and statistical errors in the derived moments, and we discuss their possible sources.
Keywords: space plasma; kappa distribution; methods; statistical analysis space plasma; kappa distribution; methods; statistical analysis
MDPI and ACS Style

Nicolaou, G.; Livadiotis, G.; Wicks, R.T. On the Determination of Kappa Distribution Functions from Space Plasma Observations. Entropy 2020, 22, 212.

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