Dissipation and Kinetic Physics of Astrophysical Turbulence

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Turbulence is one of the fundamental physical phenomena associated with fluids, gasses, and plasmas. In astrophysical phenomena, turbulence provides a mechanism of efficient energy, momentum, and particle transport thus playing a key role in the dynamics of astrophysical objects. The solar wind has served as a unique laboratory for studies of turbulence due to the availability of measurements from spacecraft. Accordingly, considerable effort has been made to study solar wind turbulence using a combination of observational, theoretical, and computational tools. While understanding of the basic physics of this phenomenon has advanced greatly, a significant number of key questions remain unanswered. This project proposes to use the Blue Waters leadership class computing system to execute ground-breaking large scale simulations to investigate how energy cascades and is ultimately dissipated in the solar wind. This study will significantly advance the state of knowledge of turbulence and will represent a very important milestone in the efforts to perform realistic modeling of solar wind turbulence. Additionally, the project results will be of great interest to a wide community of researchers working on solar wind plasma, coronal plasma, and plasma astrophysics. Overall, this project is part of a larger stream of fundamental scientific research, which is central to the mission of the NSF.One particularly challenging question, which is the focus of this proposal, is what happens to the energy that is cascaded to kinetic scales by magnetohydrodynamic (MHD) turbulence. This question is not only of basic plasma physics interest, but is also directly related to the very important problem of solar wind and solar corona heating that is crucial to understanding of the Sun-Earth interaction, but has so far eluded a conclusive solution. This study will overcome many of the limitations of existing approaches and will provide complementary information covering effects and parameter regimes inaccessible to other techniques. The planned 3D simulations on Blue Waters will reach into the MHD scales while retaining kinetic effects and will provide a glimpse into many of the crucial questions posed by the research community. Additionally, the simulations will enable detailed comparison with spacecraft observations and exploration of the role of competing processes that are simultaneously present in the simulations. The wealth of information in these simulations is akin to data collected from many spacecraft missions and warrants analysis from the community at large. As such, the simulation data resulting from the project will be made available to the community for analysis.