Experimental Investigation of Ion Heating Due to Magnetohydrodynamic Waves

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).This project concerns a laboratory investigation of ion heating processes that are hypothesized to occur in the acceleration region of the fast solar wind. The experiments proposed here will continue studies of modifications to the ion velocity distribution function that occur when Alfvén waves propagate into region of strong Alfvén speed gradients; measure changes in Alfvén wave dispersion and continue to look for evidence of reflection and ducting in regions of strong Alfvén speed gradients; determine if ion heating occurs during a turbulent cascade to high k waves at super-cyclotronic frequencies, in single specie and multi-ion species plasmas; investigate parametric decay of shear Alfvén waves at large transverse density gradients; explore the propagation of driven fast MHD waves in regions with large density gradients and look for nonlinear interactions between shear and compressional Alfvén waves with spontaneously excited MHD fast waves in the density gradient region; and compare experimental results to computational codes and analytic theories that include the effects of strong gradients. The experiments will be performed in a space-relevant, laboratory plasma with sufficient diagnostic capability to investigate the evolution of the ion velocity space distribution function of majority and minority ions as they interact with propagating Alfvén waves, to measure the detailed properties of the Alfvén waves in the plasma, and to non-invasively detect and measure the wave number spectrum of perpendicularly propagating waves. The research involves the training of new graduate students in plasma physics, improvement of the percentage of women and underrepresented groups obtaining advanced degrees in physics, involvement of undergraduates in cutting-edge scientific research, and the active engagement of K-12 students and teachers in science and math activities through a robotics-based outreach program. The international collaboration built into the proposed project will provide young scientists an opportunity to develop international collaborations and gain experience working in international teams and institutions - thereby preparing the next generation of scientists for productive research careers in a future that is likely to involve considerable international collaboration in science