Speaker
Description
Space and astrophysical plasmas are non-equilibrium systems. Turbulence is the most prominent phenomenon bridging the vast separation between large energy-containing scales and small kinetic scales. At these scales, diverse kinetic mechanisms, ranging from wave-particle interactions to micro-instabilities and magnetic reconnection, contribute to the conversion of energy between the electromagnetic field and the plasma, eventually leading to energy dissipation, plasma heating, and particle energization. Owing to the typically weak collisionality, energy conversion occurs in the entire six-dimensional phase space, giving rise to distorted non-thermal velocity distribution functions. This also implies that kinetic models are needed to fully understand the fundamental mechanisms responsible for energy conversion and dissipation in space and astrophysical plasmas.
In this talk, I will outline (some of) the most significant open questions tackled within the community in the last years, highlighting the synergy between in-situ observations and numerical simulations and the methodologies and outcomes. In particular, I will introduce the concept of phase-space turbulence, in which the production of phase-space disturbances in the plasma distribution function at different scales is envisioned as phase-space cascade processes. Finally, I will comment on the "thermodynamics" of nearly-collisionless plasmas, aka on the tension between the formal reversibility of many energy conversion mechanisms and the need for restoring irreversibility in nearly-reversible systems.
