Collaborative Research: SHINE--Stochastic Particle Acceleration by Turbulence in Solar Flares

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The observed radiation from solar flares and solar energetic particles (SEPs) indicates the presence of nonthermal particles and very hot plasmas. While it is generally believed that the source of the energy is magnetic reconnection, the origin of these high energy particles is a matter of considerable debate. Based on new observations (notably high resolution data from RHESSI), the PIs have proposed that most of the energy released is initially converted into plasma turbulence, which then accelerates particles and heats the plasma further. This team thus plans to investigate the role of anisotropic turbulence cascade and damping in the acceleration of solar plasmas. They plan to use accurate dispersion relations that go beyond simple MHD treatments in their evaluation of wave-wave and wave-particle interactions. Their goal is to incorporate these results into a solar flare model to present a self-consistent picture of flares that can be tested by observations. The Stanford PI and his associates have developed numerical codes to study particle heating, acceleration, transport, and radiation. The Wisconsin Co-PI and his group have substantial expertise in the area of magnetic plasma turbulence and have developed codes for treating turbulence in the regimes relevant to the study. Recent work by the PI and his associates has shown that turbulence can explain many features of the new observations. They expect turbulence to be present in flare plasmas and their simulations confirm this. The Co-PI has also made progress in the understanding of compressible MHD turbulence. This Stanford-Wisconsin team thus believes that incorporating the physics of turbulence generation and evolution, and its coupling with solar plasma, will now permit advances in solar flare modeling. The complementary expertise of the Stanford and Wisconsin PIs could provide the tools necessary for a breakthrough in this important problem. This research is expected to have a strong educational aspect by involving not only postdoctoral fellows and graduate students at both institutions, but also undergraduate students. The results of this research will be presented at local educational and public institutions through the auspices of Stanford's Haas Center for Public Service.