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

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The Principal Investigator (PI) will re-examine the basis for, and the limitations of, the "coherent flux tube" paradigm for coronal and interplanetary magnetic fields, in situations where magnetic fluctuations and turbulence are present. His research team will start from modeled fields in which Field Line Random Walk (FLRW) effects, as well as flux tube meandering and "shredding," cause perturbations of the standard flux tube picture, and eventually its breakdown. The PI will then progress through several models of turbulent fluctuations which give rise to flux tube irregularity, and investigate how the standard flux tube model breaks down. This work will impact our understanding of the propagation of solar energetic particles (SEPs). It will also provide valuable insights into the accuracy and limitations of standard smooth flux tube assumptions used in studying coronal structure, plasma heating models, models of the interplanetary magnetic field, and interplanetary coronal mass ejection (ICME) structure.The PI's team will investigate the diffusive random walk limit of field line transport and the delay of full randomization associated with the topological complexity of magnetic fluctuations. The latter effect has been suggested as an explanation of "dropouts" or "channeling" of SEPs, and the PI will further evaluate this concept. The PI will examine the statistical transition from closed to open field line topology that is induced by addition of broadband fluctuations, as well as the formation of flux tubes and topological structure in dynamical simulations of magnetohydrodynamic (MHD) turbulence. His team will compare identified coherent flux tube properties with solar wind data. Quantitative estimates and fully analytical theories will be used, and numerical verification will be applied as feasible. The PI asserts that this effort will result in better recognition of the limitations of the smooth flux tube models that are used in a broad range of research fields, from astrophysics to space weather prediction. A PhD student will be a key participant in this work, which will involve partnerships with scientists in Thailand and Argentina.