AGS-PRF: The Effects of Nonlinearities on the Onset and Evolution of Microinstabilities in Solar Plasma

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The postdoctoral study in geospace science is a combination of analytical, computational, and observational work to be conducted under the supervision of Prof. Kristopher Klein at the University of Arizona. The project addresses open questions in solar physics about how the solar wind is energized, and in general, about how astrophysical plasmas are heated due to particle interactions with magnetic fields. This work is important as the vast majority of visible mass in the universe is expected to be in the plasma state, in which atoms are broken up into electrons and ions that are strongly influenced by magnetic and electric fields. The study is particularly timely to interpret forthcoming observations from the Parker Solar Probe. In addition to doing cutting-edge research, the principal investigator (PI) will also mentor a summer student’s research project and develop an undergraduate educational module on space physics, which will contribute toward her professional development.Microinstabilities are known to play a large role in the energy transfer and evolution of astrophysical plasmas including the solar wind. Most descriptions of the evolution and onset of microinstabilities only include linear terms, ignoring nonlinear effects. However, the onset and evolution of many of these instabilities is highly dependent on non-thermal features of the particle velocity distribution function, in particular, regions of trapped particles in finite amplitude magnetic fields. The primary questions to be investigated in this postdoctoral study are (i) the extent to which nonlinear effects, such as trapped and passing particles, affect the onset and evolution of microinstabilities in the solar plasma, and (ii) the parameter regimes where the nonlinearities need to be taken into account. The project will develop an analytical model for the evolution and onset of the instabilities, drawing on quasilinear theory and the PI’s thesis work on trapped and passing particles. The analytical model will be validated using kinetic simulations in conjunction with a statistical analysis of fluctuations observed in the solar wind.The principal investigator will mentor an REU student’s research project at the University of Arizona and develop an educational module to introduce undergraduates to current research questions in space science and plasma physics. This module will be made available to the scientific as well as education community.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.