Collaborative Research: Electron Heat Flux Regulation in the Solar Wind

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Understanding and characterizing fundamental processes that take place within the heliosphere and throughout the universe is important, and it could be vital for future human explorations of space, as well as for studying the space environmental impact on modern civilization. Solar wind is the medium through which harmful radiation travels. An accurate description of the solar wind is necessary to understand the propagation of these disturbances from the Sun to the Earth. This project studies solar wind physics. The work supports training of a graduate student and post-doctoral researcher.The research aims to address the compelling science question of "what regulates the solar wind heat flux?" The electrons in the solar wind efficiently conduct heat, thus carrying the heat flux along the anti-sunward direction. Among physical processes that regulate the heat flux, whistler heat-flux instabilities are suggested as being important in the collisionless heat flux regime, while in the collisional regime, the binary collisions are the classical regulation mechanism. Both processes compete against the radial expansion effects. The relative importance of these competing processes, that is, instabilities, collisions, and expansion, remains an outstanding and thus, together they constitute a compelling research topic. The project will use the self-consistent quasilinear theory and kinetic theory of collisions in magnetized plasma to model the evolution of the waves and electron heat flux in the radially-varying solar wind. The theory will be driven by inputs from, and tested against, the well-calibrated measurements of the solar wind electron distribution function from various spacecraft between 0.3 and 1 AU, as well as proton parameters, magnetic field and plasma wave data. Such an integrated and collaborative research on the nature of solar wind electrons and the heat flux they carry will greatly contribute toward improving our understanding of the fundamental processes that take place within the heliosphere.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.