The Evolution of Magnetic Rayleigh-Taylor Unstable Plumes and Hybrid KH-RT Instability into A Loop-like Eruptive Prominence

MRT unstable plumes are observed in a loop-like eruptive prominence using SDO/AIA observations. The small-scale cavities are developed within the prominence, where perturbations trigger dark plumes (P1 \& P2) propagating with the speed of 35-46 km s$^{-1} $. The self-similar plume formation shows initially the growth of linear MRT unstable plume (P1), and thereafter the evolution of non-linear single mode MRT unstable second plume (P2). The Differential Emission Measure (DEM) analysis shows that plumes are less denser and hotter than the prominence. We have estimated the observational growth rate for both plumes as 1.32$\pm$0.29$\times$ 10$^{-3}$ s$^{-1}$ and 1.48$\pm$0.29$\times$ 10$^{-3}$ s$^{-1}$ respectively, which are comparable to the estimated theoretical growth rate (1.95$\times$ 10$^{-3}$ s$^{-1}$) . The nonlinear phase of an MRT unstable plume (P2) may collapse via Kelvin-Helmholtz vortex formation in the downfalling plasma. Later, a plasma thread has been evident in the rising segment of this prominence. It may be associated with the tangled field and Rayleigh-Taylor instability. The tangled field initiates shearing at the prominence-cavity boundary. Due to this shear motion, the plasma downfall has occurred at the right part of the prominence-cavity boundary. It triggers the characteristic of KH unstable vortices and MRT unstable plasma bubbles propagating at different speeds and merging with each other. The shear motion and lateral plasma downfall may initiate hybrid KH-RT instability there.

Sudheer K. Mishra, A.K. Srivastava · 2019