2017/07/31 by Yi-Min Huang, Luca Comisso, A. Bhattacharjee
Mathematics · Physics and Astronomy · #Amplitude #Current sheet #Geometry #Growth rate #Instability #Ionosphere and magnetosphere dynamics #Magnetic confinement fusion research #Magnetic reconnection #Magnetohydrodynamics #Mathematics #Mechanics #Nonlinear system #Physics #Plasma #Plasmoid #Quantum mechanics #Solar and Space Plasma Dynamics #Statistical physics #Wavenumber #astro-ph.HE #astro-ph.SR #physics.flu-dyn #physics.plasm-ph #physics.space-ph
paper · pdf · doi:10.3847/1538-4357/aa906d
published as Astrophysical Journal, 849, 75 (2017)
arxiv created 2017/10/03 · openalex publication_date 2017/11/03 · arxiv updated 2017/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Abstract The scaling of the plasmoid instability maximum linear growth rate with respect to the Lundquist number S in a Sweet–Parker current sheet, , indicates that at high S , the current sheet will break apart before it approaches the Sweet–Parker width. Therefore, a proper description for the onset of the plasmoid instability must incorporate the evolving process of the current sheet. We carry out a series of two-dimensional simulations and develop diagnostics to separate fluctuations from an evolving background. It is found that the fluctuation amplitude starts to grow only when the linear growth rate is sufficiently high to overcome advection loss and the stretching effect due to the outflow. The linear growth rate continues to rise until the sizes of plasmoids become comparable to the inner layer width of the tearing mode. At this point, the current sheet is disrupted and the instability enters the early nonlinear regime. The growth rate suddenly decreases, but the reconnection rate starts to rise rapidly, indicating that current sheet disruption triggers the onset of fast reconnection. We identify important timescales of the instability development, as well as scalings for the linear growth rate, current sheet width, and dominant wavenumber at disruption. These scalings depend not only on the Lundquist number, but also on the noise amplitude. A phenomenological model that reproduces scalings from simulation results is proposed. The model incorporates the effect of reconnection outflow, which is crucial for yielding a critical Lundquist number S c below which disruption does not occur. The critical Lundquist number S c is not a constant value, but has a weak dependence on the noise amplitude.