Interlink between turbulence, magnetic reconnection, and cosmic-ray production in non-relativistic and relativistic astrophysical plasmas

Abstract

Magnetized turbulence is ubiquitous in astrophysical plasmas and crucial for the formation of dense structures and stars, the stability of molecular clouds, the amplification of magnetic fields, magnetic reconnection, and the production and diffusion of cosmic rays. During the last decade it became clear, that the cascade of magnetized turbulence transferring energy from the large-scale motions to the scale of dissipation cannot be completely understood without taking into account magnetic reconnection, a fundamental process in magnetized plasmas responsible for topological changes of magnetic fields and associated with the release of magnetic energy in regions of magnetic field annihilation. On the other hand, magnetic reconnection in the presence of external or self-generated turbulence becomes fast. These facts indicate a strong and intimate relation between these two phenomena and their importance for the dynamics of astrophysical systems. Moreover, they can be responsible for non-thermal radiation, acting as first-order Fermi process, an acceleration mechanism able to produce high-energy cosmic-rays from thermal particles in non-relativistic and relativistic systems without the requirement of the presence of strong shocks. Therefore, a deep understanding of these three phenomena: magnetized turbulence, magnetic reconnection, and cosmic-ray acceleration, and the interlink between them is a key to understand dynamics of astrophysical plasmas. For several decades a significant effort has been put in understanding these phenomena independently. In the last years, however, the scientific community has realized about the importance of understanding the relation between these processes. The aim of this project is to perform a systematic theoretical study supported by numerical modeling of the interlink between turbulence, magnetic reconnection, and cosmic-ray production in non-relativistic and relativistic plasmas, with focus on strongly and weakly collisional regimes, covering vast majority of astrophysical plasmas. We aim to investigate the role of instabilities in the generation of local turbulence, the strength and properties of this turbulence, its effects of the global reconnection rate, the efficiency of acceleration mechanism based on turbulent magnetic reconnection, as well as, the dependencies of these processes on the plasma-$\beta$, Lundquist number, and the degree of pressure anisotropy. The conclusions from these studies will be applied to understand the satellite measurements of the interactions between solar wind and magnetosphere, the role of turbulent reconnection in the solar corona dynamics, the role of magnetic reconnection diffusion in star formation process, the observations of non-thermal radiation in Colliding-Wind Binaries (CWB), Gamma-Ray Bursts (GRB) and Active Galactic Nuclei (AGN). (AU)