Three-dimensional Velocity Measurements in Solar Prominence Bubbles and Combined Kelvin-Helmholtz/Rayleigh-Taylor Instability
Abstract
We present measurements of flow velocities in solar prominences that display so-called "prominence bubble" events. Prominence bubbles are large-scale buoyant intrusions into prominences that rise from below and penetrate into the overlying plasma. They are believed to be due to magnetic flux emergence below prominences and can trigger Rayleigh-Taylor and Kelvin-Helmholtz instability flows as they interact with the overlying prominence. Prominence bubbles frequently result in the formation of plumes that rise into, or entirely through, the overlying prominence. This presents a mechanism for increasing magnetic flux and helicity in the associated coronal magnetic flux tubes, which are key for their eventual loss of equilibrium and eruptions as coronal mass ejections (CMEs). In this presentation, Hinode/Solar Optical Telescope (SOT) and Interface Region Imaging Spectrograph (IRIS) observations are analyzed to infer three-dimensional flow vectors in the "boundary layer" above several prominence bubble events. IRIS Doppler velocity measurements indicate flow speeds of 50-100 km/sec perpendicular to the sky plane, consistent with flow speeds inferred from combined Kelvin-Helmholtz/Rayleigh-Taylor instability analysis using typical quiescent prominence density and magnetic flux density values. With these typical values, flow speeds and magnetic flux densities within the bubbles can be inferred to be on the order of 100 km/sec and 10 Gauss, respectively. We discuss the implications of these novel results, and in particular, the potential for strong shear flows at the bubble boundary to trigger Kelvin-Helmholtz instability waves that develop into large-scale Rayleigh-Taylor instability plumes.
- Publication:
-
42nd COSPAR Scientific Assembly
- Pub Date:
- July 2018
- Bibcode:
- 2018cosp...42E.293B