Periodic Reporting for period 1 - ASTROMULTISCALE (Multiscale dynamics of astrophysical plasmas: pressure-anisotropy-driven instabilities and large-scale dynamical processes)
Reporting period: 2015-06-01 to 2017-05-31
Results of the project are expected to be important for general plasma physics as related to the problem of multiscale phenomena in plasmas and coupling between microphysics and macrophysical processes. The study falls into the field of fundamental research aiming at general understanding of pressure-anisotropy-related phenomena in plasmas with possible direct applications to other fields: dynamics of galaxy-cluster plasmas, dynamical processes in stellar winds and planetary magnetospheres. Due to numerous practical applications of plasmas, results of the project potentially may have some practical applications in future.
In terms of objectives, the project focuses on the investigation of (i) the transfer of the energy between the components: kinetic (mechanical), thermal and magnetic, in the presence of pressure anisotropy and related instabilities, (ii) constraints on the pressure anisotropy and other variables describing the state of the system, (iii) development of computational tools for numerical simulations of pressure-anisotropic plasmas. The study includes links between the microphysics and large-scale dynamics and the role of instabilities and effective viscosity of pressure-anisotropic plasmas. Theoretical results are contrasted with spacecraft measurements in turbulent solar wind.
The influence of the pressure anisotropy on plasma dynamics was investigated in an extensive series of numerical simulations of plasmas with different ratio of the thermal and magnetic energy density. A new mechanism of the transfer of the kinetic energy of plasma flows to the thermal energy has been identified as specifically related to the presence of the pressure anisotropy. The mechanism can be interpreted in terms of effective viscosity leading to constraints on the pressure anisotropy.
Constraints on the amplification of the magnetic field (so-called dynamo problem) were studied as related to the pressure-anisotropy generation in collisionless or weakly-collisional plasmas. A hierarchy of plasma models of increasing complexity was considered in the context of constraints on the small-scale dynamo action. It was shown that the conservation of the invariants of so-called double-adiabatic or CGL theory makes the maximum available magnetic energy in the dynamo process to scale inversely with the ratio of the thermal and magnetic energy density.
Results obtained in the project has been published in two peer-reviewed papers and presented in eight conference/seminar talks.
Results of the project have possible direct applications to other fields of fundamental research: dynamics of collisionless turbulent plasma flows, dynamics of galaxy-cluster plasmas, dynamical processes in stellar winds and planetary magnetospheres. Due to numerous practical applications of plasmas, results of the project potentially may have some practical applications in future.