Role of turbulent transport in the evolution of the κ distribution functions in the plasma sheet

Abstract

We studied the evolution of ion and electron distribution functions, approximated by distributions, in the plasma sheet with the distance from the Earth using the data of the Time History of Events and Macroscale Interactions during Substorms spacecraft mission. Five events were used to calculate the main parameters of the distribution. For these events at least four spacecraft were aligned along the tail between approximately 7 and 30 R E . It was found that for the majority of events the values of increase tailward. The observed radial profiles could be related to the inner magnetosphere sources of particle acceleration and to the net tailward transport of particles. This net transport is the result of a balance between the average regular bulk transport toward the Earth and the turbulent transport by eddies in the tailward direction.

Ion and Electron κ Distribution Functions Along the Plasma Sheet

“…Their results suggest a transition from low values close to Earth to higher values at the tail. For ions, three of the five cases studied by Stepanova and Antonova (2015) were consistent with an evolution from ∼ 5 to ∼ 7, on average. These results were consistent with Viñas et al (2005) and Benson et al (2013), who found ∼ 2 near the magnetic midnight, in the low-latitude magnetosphere (small Z) near the plasmasphere.…”

“…They have been successfully used, both observationally and theoretically (e.g., Navarro et al, 2015;Pierrard & Meyer-Vernet, 2017;Viñas et al, 2015;Yoon & Livadiotis, 2017), to describe particle distribution functions for velocity or energy (PEDF) 10.1029/2018GL078631 in a number of plasma environments, from the Earth's and other planets magnetospheres (Benson et al, 2013;Kirpichev et al, 2017;Viñas et al, 2005) to solar radio bursts (Cairns et al, 2017). For particles energy fluxes, the distribution can be written (Stepanova & Antonova, 2015) as For very large values of the index the distribution tends to the Maxwellian case, thereby representing particles close to thermal equilibrium, with relatively short thermalization times and uncorrelated behavior.…”

“…On the other hand, low values indicate plasmas out of thermal equilibrium or collisionally young plasmas that have not had enough time to relax toward a Maxwellian distribution. For particles energy fluxes, the distribution can be written (Stepanova & Antonova, 2015) as…”

“…In this work we use the GSM coordinate system for the variables X, Y, and Z. For ions, three of the five cases studied by Stepanova and Antonova (2015) were consistent with an evolution from ∼ 5 to ∼ 7, on average. In the other two cases, however, the values obtained at larger distances were as low as those found close to Earth.…”

Ion leakage at dayside magnetopause in case of high and low magnetic shears

“…In spite of comparatively large fluctuations, averaged values of the kappa parameter in the magnetosheath are similar to the kappa values measured inside the magnetosphere. Such values are typical for the plasma sheet and outer ring current [ Christon et al , ; Pissarenko et al , ; Stepanova and Antonova , ]. This is good evidence for a magnetospheric origin for these particles.…”