A one dimensional, electrostatic Vlasov model for the generation of suprathermal electron tails in solar wind conditions

Abstract

[1] Space and laboratory collisionless plasmas are most often out of local thermodynamic equilibrium. In particular, their charged particle velocity distributions usually differ from simple Maxwellian distributions and exhibit a great variety of anisotropies and components such as suprathermal beams and tails. Here we propose a new model responsible for a ''local'' origin of electron suprathermal tails. The model is based on adding a high and a low frequency external forcing to the Vlasov-Poisson system of equations. The first one represents mainly the thermal noise electric field generated by charge separation effects. The second one represents the energy injection resulting from the energy cascade generated by the large scale fluid (MHD) turbulence. We find that in typical solar wind conditions, our model could be the base of a full three dimensional, electromagnetic model capable of explaining the local generation of the electron halo population observed on the electron distribution function.Citation: Califano, F., and A. Mangeney (2008), A one dimensional, electrostatic Vlasov model for the generation of suprathermal electron tails in solar wind conditions,

Suprathermal Particle Populations in the Solar Wind and Corona

“…The resulting electrostatic modes would be rapidly damped out leading to the formation of suprathermal electron distributions near the Sun (Viñas et al, 2000). Due to large scale density fluctuations generated by the solar wind MHD turbulence, the Langmuir wave packets are trapped in the proton density holes leading to an efficient acceleration of electrons and formation of suprathermal tails (Califano & Mangeney, 2008;Yoon et al, 2006).…”

“…The nonlinear mechanisms of acceleration are usually investigated in numerical experiments, and the simulations indicate that the results of the quasilinear theory are applicable to the finite amplitude wave fluctuations typically observed in the solar wind and magnetosphere (Califano & Mangeney, 2008;Leubner, 2000;Roberts & Miller, 1998;Summers & Ma, 2000). It appears that the traditional quasi-linear theory provides a reasonable description of particle scattering and acceleration by a weak plasma turbulence.…”

Parallel velocity mixing yielding enhanced electron heating during magnetic pumping

“…Much of the work on a possible explanation for this additional heating centres on wave–particle interactions as the primary heating mechanism, where energy is provided by the turbulence associated with propagating waves (Kennel & Petschek 1966; Ergun et al 1998; Vinas, Wong & Klimas 2000; Vocks et al 2005; Rhee, Ryu & Yoon 2006; Califano & Mangeney 2008). In these models, particles are energized at the resonant velocities, where , and with .…”

ViDA: a Vlasov–DArwin solver for plasma physics at electron scales

“…In such systems, energy is typically injected at large fluid scales and cascades towards smaller scales, driving the system to cross three different physical regimes, ranging from fluid (magnetohydrodynamics, Hall-MHD) to ion kinetic and eventually to electron kinetic scales. This multi-scale physics is the direct consequence of the weak plasma collisionality, that characterizes solar-wind and astrophysical plasmas (Kulsrud 2005; Califano & Mangeney 2008; Bruno & Carbone 2016) as well as fusion device dynamics, where collisions can become effective at scales smaller than the electron kinetic scales (Falchetto et al. 2008).…”