Speaker
Dr. Luca Sorriso-Valvo
CNR-Nanotec
Date 2017.03.08(Wed)
Time 10:30am
Place S4-625
Abstract:
Space and astrophysical plasmas often show turbulent fluctuations on a broad range of scales. The associated dissipative and/or dispersive processes resulting in both thermal and nonthermal energization of particles are still not fully understood. Decades of spacecraft observations have shown that the solar wind provides a great opportunity to study in-situ plasma turbulence, representing a natural “wind tunnel”. Measurements indicate that solar wind plasma is constantly heated during its expansion in the heliosphere, but at the same time solar wind electrons, protons and alpha particles show clear non-Maxwellian features of distribution functions (e.g. beams and energetic tails), suggesting that both heating and acceleration are at work. In order to understand which mechanisms are responsible for dispersion and dissipation of the energy carried by the turbulent fluctuations, the properties of solar wind turbulence must be known in great detail.
One of the main features of turbulent flows is intermittency, namely the nonlinear generation of highly energetic small-scale structures, such as vortexes and current sheets. These are often associated with localized heating or particle accelerations, as evidenced by numerical simulations. We will show here how to describe the properties of intermittency in solar wind turbulence and how to connect them to energy dissipation. Finally, we will outline the forthcoming challenges in the identification of the energy dissipation mechanisms, also highlighting the compelling need for a dedicated new space mission.