2006/08/31 by Masanori Nakamura, Hui Li, Shengtai Li · 3 citations
Biochemistry, Genetics and Molecular Biology · Physics and Astronomy · #Classical mechanics #Current sheet #Geomagnetism and Paleomagnetism Studies #Instability #Ionosphere and magnetosphere dynamics #Jet (fluid) #Kink instability #Magnetic field #Magnetic flux #Magnetic pressure #Magnetic reconnection #Magnetization #Magnetohydrodynamic drive #Magnetohydrodynamics #Mechanics #Physics #Solar and Space Plasma Dynamics #Tower #astro-ph
paper · pdf · doi:10.1086/510361
published as Astrophys.J.656:721-732,2007 · 12 pages, 10 figures, submitted to ApJ
arxiv created 2006/08/31 · openalex publication_date 2007/02/14 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Stability properties of "magnetic tower" jets propagating in a gravitationally stratified background have been examined by performing three-dimensional magnetohydrodynamic simulations. The current-carrying, Poynting flux-dominated magnetic tower jet, which possesses a highly wound helical magnetic field, is subject to the current-driven instability (CDI). We find that, under general physical conditions including small perturbations in the initial background profiles, the propagating magnetic tower jets develop the nonaxisymmetric, m = 1 kink mode of the CDI. The kink mode grows on the local Alfvén crossing timescale. In addition, two types of kink modes appear in the system. At the central region where external thermal pressure confinement is strong, only the internal kink mode is excited and will grow. A large distance away from the central region where the external thermal pressure becomes low, the external kink mode is observed. As a result, the exterior of magnetic tower jets will be deformed into a large-scale wiggled structure. We also discuss extensively the different physical processes that contribute to the overall stability properties of the magnetic tower jets. Specifically, when the jet propagates in an initially unperturbed background, we find that it can survive the kink mode beyond the point predicted by the well-known Kruskal-Shafranov (K-S) criterion. The stabilization in this case comes mainly from the dynamical relaxation of magnetic twists during the propagation of magnetic towers; the magnetic pitch is reduced, and the corresponding K-S critical wavelength becomes longer as the tower jet proceeds. Furthermore, we show that the pressure-driven and Kelvin-Helmholtz instabilities do not occur in the magnetic tower jets. This strongly suggests that the CDI is the primary reason for the wiggling structures in jets.