Sunspots and the physics of magnetic flux tubes. X - On the hydrodynamic instability of buoyant fields

Abstract

view Abstract Citations (44) References (56) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Sunspots and the physics of magnetic flux tubes. X - On the hydrodynamic instability of buoyant fields Tsinganos, K. C. Abstract The hydrodynamics of cylindrical buoyant bubbles (magnetic flux tubes) in an atmosphere is examined. Their dynamical stability is considered, with particular attention to the Rayleigh-Taylor and Kelvin-Helmholtz instabilities. The instabilities are sufficient to cause fragmentation in the absence of some strong stabilizing effect such as surface tension or an internal azimuthal magnetic field. The results of the stability analysis are first applied to rising gas bubbles in liquids. Then, since agreement with the experimental data is found, the results are applied to the similar problem of the rising magnetic flux in the sun. Magnetic flux tubes in a fluid velocity field are intrinsically unstable, unless twisted. With the known dynamical limits on the degree of twisting, an upper limit on the diameter of the order of a few hundred kilometers is found for the stability of individual flux tubes in the photosphere. Observations show that tubes, except when clustered to form sunspots, are generally not larger than this amount. Therefore, it is suggested that the hydrodynamic instability of larger tubes is a prime cause of their absence from the solar photosphere. Publication: The Astrophysical Journal Pub Date: July 1980 DOI: 10.1086/158160 Bibcode: 1980ApJ...239..746T Keywords: Buoyancy; Flow Stability; Magnetic Flux; Magnetohydrodynamic Stability; Solar Atmosphere; Solar Physics; Sunspots; Bubbles; Dynamic Stability; Flow Velocity; Hydrodynamics; Kelvin-Helmholtz Instability; Photosphere; Taylor Instability; Velocity Distribution; Solar Physics full text sources ADS |