Quiescent prominence dynamics observed with the Hinode Solar Optical Telescope . II. Prominence Bubble Boundary Layer Characteristics and the Onset of a Coupled Kelvin-Helmholtz Rayleigh-Taylor Instability
arXiv:1707.05265 · doi:10.3847/1538-4357/aa95b6
Abstract
We analyze solar quiescent prominence bubble characteristics and instability dynamics using Hinode/Solar Optical Telescope (SOT) data. We measure bubble expansion rate, prominence downflows, and the profile of the boundary layer brightness and thickness as a function of time. The largest bubble analyzed rises into the prominence with a speed of about 1.3 km/s until it is destabilized by a localized shear flow on the boundary. Boundary layer thickness grows gradually as prominence downflows deposit plasma onto the bubble with characteristic speeds of 20 - 35 km/s. Lateral downflows initiate from the thickened boundary layer with characteristic speeds of 25 - 50 km/s, "draining" the layer of plasma. Strong shear flow across one bubble boundary leads to an apparent coupled Kelvin-Helmholtz Rayleigh-Taylor (KH-RT) instability. We measure shear flow speeds above the bubble of 10 km/s and infer interior bubble flow speeds on the order of 100 km/s. Comparing the measured growth rate of the instability to analytic expressions, we infer a magnetic flux density across the bubble boundary of ~10^{-3} T (10 gauss) at an angle of ~70 degrees to the prominence plane. The results are consistent with the hypothesis that prominence bubbles are caused by magnetic flux that emerges below a prominence, setting up the conditions for RT, or combined KH-RT, instability flows that transport flux, helicity, and hot plasma upward into the overlying coronal magnetic flux rope.
17 pages, 7 figures
References in corpus (12)
- The Solar Optical Telescope for the Hinode Mission: An Overview
- The Magnetic Rayleigh-Taylor Instability in Three Dimensions
- Nonlinear Evolution of the Magnetohydrodynamic Rayleigh-Taylor Instability
- The discovery of geomagnetically trapped cosmic ray antiprotons
- Rayleigh-Taylor instability in prominences from numerical simulations including partial ionization effects
- Open questions on prominences from coordinated observations by IRIS, Hinode, SDO/AIA, THEMIS, and the Meudon/MSDP
- The Kelvin-Helmholtz Instability at CME-Boundaries in the Solar Corona: Observations and 2.5D MHD Simulations
- The magnetic field configuration of a solar prominence inferred from spectropolarimetric observations in the He I 10830 A triplet
- Morphology and dynamics of solar prominences from 3D MHD simulations
- Solar prominences: 'double, double ... boil and bubble'
- Helical motions of fine-structure prominence threads observed by Hinode and IRIS
- Investigating prominence turbulence with Hinode SOT Dopplergrams