SHINE: Coronal and Interplanetary Magnetic Field: Structure, Topology, Flux Tubes, Transport, and Application to Energetic Particles

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As the scientific motivation for this project, the principal investigator (PI) and his team note that the space physics community currently relies on solar magnetic field models that assume it is meaningful to represent flux tubes as coherent objects that extend over distances ranging from fractions of a solar radius to many Astronomical Units. In order to place this fundamental assumption on a firmer basis, the PI's team will examine the limitations of this "coherent flux tube" paradigm when magnetic fluctuations are present and they will study how to extend beyond this conceptual framework using several approaches. The team will apply magnetic field models and nonlinear transport theory to quantify Field Line Random Walk effects, as well as the flux tube meandering and "shredding" that causes the eventual breakdown of the standard flux tube scenario. The team will investigate these phenomena using "Reduced Magnetohydrodynamics" (Reduced MHD) physics models, an approach that is well tested in solar corona studies. The PI's team will also study the often neglected implications of isotropic field line and particle transport, where particle trapping becomes very important. The team will examine the relationship between field line transport and the intermittent character of real turbulent fields, and apply this knowledge to examine the well-known "dropouts" and "channeling" of solar energetic particles (SEPs) that have been observed. The team will investigate the time-dependent interaction of flux tubes by introducing the concept of "component interchange reconnection" and exploring its consequences for the topological structure of magnetic fields in the solar wind and in dynamical simulations of MHD turbulence. The broader impacts of this effort include improving our recognition of the limitations of existing flux tube models, and how these limitations apply to research areas ranging from astrophysics to space weather forecasting. In particular, this work will have an immediate impact on our understanding of the propagation of SEPs in a space weather context. The PI will also provide mentoring for several postdoctoral fellows and widely disseminate these research results at solar physics community workshops.