Laboratory Characterization of Co-Propagating Alfven Wave Interactions

The behavior of turbulence is one of the most hotly debated topics among researchers, and understanding this behavior has been a long-standing goal of the Heliophysics community. Turbulence in the near-sun solar wind is imbalanced, meaning there are many more waves moving away from the sun than towards the sun; this imbalance may impact which interactions between waves are most important for moving energy from large to small scales in the solar wind. To better understand how energy moves through this system, the team will conduct scaled laboratory experiments to precisely characterize two of these wave-wave interactions and compare them to a third (previously studied) interaction. These experiments will quantitatively demonstrate the relative importance of these interactions, which can inform interpretation of spacecraft data and future simulation efforts. Additionally, this research is led by and will primarily support an early-career researcher from an underrepresented group who devotes substantial time to a variety of community efforts in broaden participation of the full spectrum of diverse talents in STEM. The team will participate in outreach programs for public education. This work includes an international collaboration component. The objective of this project is to better understand wave-wave interaction processes which may be controlling imbalanced solar wind turbulence at ion scales, particularly in the solar corona and inner solar wind. Specifically, the team will conduct a series of laboratory experiments on LArge Plasma Device (LAPD) located at the University of California, Los Angeles to investigate the detailed behavior of two interactions between co-propagating Alfvén waves: a novel interaction driven by Hall physics, and the already known dispersive interaction. The team will conduct a scaling study of the transition between these two co-propagating interactions and compare them to the often-dominant MHD counter-propagating interaction. These comparisons will help establish which processes may be most active in driving the dynamics of imbalanced magnetized plasma turbulence. Such efforts are particularly timely, as Parker Solar Probe is now studying precisely the region of space where the interactions occur. The results of this project could influence the plasma dynamics, allowing the team to inform interpretation of Parker Solar Probe measurements and related simulations. 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.