Alfvén waves, laboratory plasmas, space plasmas, astrophysical plasmas, geophysics, hybrid simulation, MHD
These studies make use of the Large Plasma Device (LAPD) at UCLA, a 20-meter long linear magnetized plasma device, to investigate various processes of basic plasma physics related to Alfven waves and their applications to space and astrophysical science, e.g. solar coronal heating, solar wind turbulent cascades.
Alfven waves are a main carrier of energy over long distances in space plasma. The dissipation of Alfven wave energy through nonlinear interactions may be powerful enough to heat up the coronal region and release/accelerate the solar wind — a stream of plasma particles ejected from the Sun.
Of particular interest here is Alfven wave parametric instabilities, where energy transfer and redistribution happen when the driving Alfven wave couples to other collective plasma modes. For example, the Alfven wave parametric decay instability (PDI) involves a large amplitude Alfven wave decaying into a child Alfven wave and an ion sound wave. Yet, direct observations of Alfven wave parametric instabilities in both laboratory and space plasma remains inconclusive due to various challenges.
We aim to investigate PDI and other instabilities on LAPD under well controlled conditions. To prepare for such experiments, we have developed 3D kinetic simulations that are tailored to model LAPD Alfven wave studies using realistic geometries and wave and plasma conditions [1-3]. These capabilities will enable detailed characterization and prediction of excitation conditions needed to drive PDI in LAPD. The projects will also devise novel methods to measure the growth rates of the instability and perform detailed scaling studies of PDI versus the LAPD parameters available [4]. The study will aid our understanding of the role of PDI in the solar terrestrial plasma system and help validate theories and our computational models.
We anticipate that these studies can be easily extended to a broad range of investigations [5] involving close synergy between experiment, simulation and theory.
The research has been supported by DOE and NASA.
[1] F. Li, X. Fu, and S. Dorfman, Parametric decay of Alfvénic wave packets in nonperiodic low-beta plasmas, The Astrophysical Journal, 924, 33 (2022).
[2] F. Li, X. Fu, and S. Dorfman, Hybrid simulation of Alfvén wave parametric decay instability in a laboratory relevant plasma, Physics of Plasmas 29, 092108 (2022)
[3] F. Li, X. Fu, and S. Dorfman, Effects of wave damping and finite perpendicular scale on three-dimensional Alfven wave parametric decay in low-beta plasmas, to submit.
[4] F. Li, et al. Seeded parametric decay of small-scale Alfven waves, in prep.
[5] F. Li, Excitation and dynamics of Alfven wave parametric decay with relevance to a linear device, in prep.
Public talk on solar wind and Alfven waves (Nov 2022)