Using the kappa function to investigate hot plasma in the magnetospheres of the giant planets

Abstract

Planetary magnetospheres contain two general classes of charged particles: low energy "thermal" particles (generally E < 1 keV) usually described by a Maxwellian distribution and "hot" particles (E > 10 keV), variously called superthermal or "energetic" particles, which are described by a power law distribution. The kappa or κ function combines aspects of both Maxwellian and power law forms to provide a reasonably complete description of the particle distribution from low to high energies. Fits of the data to the kappa distribution can reveal particle density, temperature, pressure, and convection velocity, all of which are key parameters of magnetospheric physics. This paper summarizes the use of the kappa distribution and its variants to investigate the plasma properties of the magnetospheres of the giant planets Jupiter, Saturn, Uranus, and Neptune. While the κ function was used to derive convective motions in previous investigations, temperatures, and pressures at Jupiter and Saturn, it was not an optimum fit for hot plasmas at Uranus and Neptune, and in many instances may not be the optimum representation of magnetospheric plasmas.

Misestimation of temperature when applying Maxwellian distributions to space plasmas described by kappa distributions

“…Kappa distributions are characterized by their high energy tail which is not always clearly observed because of the low plasma intensities in the high energy range. Nevertheless, many analyses used successfully kappa distributions to describe observations in several plasma environments, where the Maxwell distribution clearly fails to describe the high energy tails of the observed distributions: solar wind (e.g., Maksimovic et al 1997;Pierrard et al 1999;Chotoo et al 2000;Mann et al 2002;Marsch 2006;Zouganelis et al 2008;Štverák et al 2009;Livadiotis and McComas 2013b;Yoon 2014;Heerikhuisen et al 2015;Pierrard and Pieters 2015), planetary magnetospheres (e.g., Christon 1987;Collier and Hamilton 1995;Jurac et al 2002;Pisarenko et al 2002;Kletzing et al 2003;Mauk et al 2004;Schippers et al 2008;Dialynas et al 2009;Ogasawara et al 2012;Carbary et al 2014;Qureshi et al 2015;Stepanova and Antonova 2015), the outer heliosphere and the inner heliosheath (e.g., Decker and Krimigis 2003;Decker et al 2005;Heerikhuisen et al 2008;Zank et al 2010;Livadiotis et al 2011;2012;Livadiotis and McComas 2011a;2012), and other various plasma-related analyses (e.g., Milovanov and Zelenyi 2000;Saito et al 2000;Yoon et al 2006;Raadu and Shafiq 2007;Tribeche et al 2009;Hellberg et al 2009;Livadiotis and McComas 2009;…”

Kappa Distributions: Statistical Physics and Thermodynamics of Space and Astrophysical Plasmas

“…The kappa distributions have a tremendous number of applications in space and astrophysical plasmas, such as the inner heliosphere, including solar wind (e.g., [13,20,26,[38][39][40][41][42][43][44][45][46][47][48]), solar spectra (e.g., [49,50]), the solar corona (e.g., [51][52][53][54]), solar energetic particles (e.g., [55,56]), corotating interaction regions (e.g., [57]), and related solar flares (e.g., [21,33,58,59]); planetary magnetospheres, including the magnetosheath (e.g., [60,61]), magnetopause (e.g., [62]), magnetotail (e.g., [63]), ring current (e.g., [64]), plasma sheet (e.g., [65][66][67]), magnetospheric substorms (e.g., [68]), Aurora (e.g., [69]); magnetospheres of giant planets like the Jovian (e.g., [70][71][72]), Saturnian (e.g., [73][74][75][76]), Uranian (e.g., [77]), and Neptunian (e.g., <...>…”

Polytropes in plasmas described by kappa distributions – Application in atmospheric modelling

“…The kappa distributions have become increasingly widespread across the physics of space plasmas, describing particles in the heliosphere, from the solar wind and planetary magnetospheres to the heliosheath and beyond, the interstellar and intergalactic plasmas: inner heliosphere , including solar wind, [ 12–26 ] solar spectra, [ 27–29 ] solar corona, [ 30–33 ] solar energetic particles, [ 34,35 ] corotating interaction regions, [ 36 ] and solar flares related; [ 4,37–39 ] planetary magnetospheres , including magnetosheath, [ 40,41 ] magnetopause, [ 42 ] magnetotail, [ 43 ] ring current, [ 44 ] plasma sheet, [ 45–46 ] magnetic reconnection, [ 47 ] magnetospheric substorms, [ 48 ] Aurora, [ 49 ] magnetospheres of giant planets, such as Jovian, [ 50–53 ] Saturnian, [ 54–56 ] Uranian, [ 57 ] Neptunian, [ 58 ] magnetospheres of planetary moons, such as Io [ 59 ] and Enceladus, [ 60 ] cometary magnetospheres; [ 61,62 ] outer heliosphere and the inner heliosheath; [ 63–78 ] (d) beyond the heliosphere , including HII regions, [ 79 ] , planetary nebula, [ 80,81 ] and supernova magnetospheres; [ 82 ] and in cosmological scales. [ 83 ]…”