Spectro-imagery of an active tornado-like prominence: Formation and evolution

The nature of flows in tornado-prominences is an open issue. While the AIA imager aboard Solar Dynamics Observatory (SDO) allowed us to follow global structure a tornado-like prominence during five hours, Interface Region Imaging Spectrograph (IRIS), and Multi subtractive Double pass spectrograph (MSDP) permitted obtain plasma diagnostics its fine structures. We aim address two questions. Is observed rotation conceptually acceptable flux rope magnetic support configuration with dips? How density distributed prominence? calculated line-of-sight velocities non-thermal line widths using Gaussian fitting for Mg II lines bisector method H-alpha line. determined electron from integrated intensities profile methods 1D NLTE radiative transfer theory models. H-alpha, h k fits field dips. Coherent Dopplershifts red- blue-shifted areas both were detected along rapidly-changing vertical horizontal However, tornado at top consists multiple-fine threads opposite suggesting counter streaming rather than rotation. Surprisingly we found that could be larger (10^11 cm^{-3}) inner part prominence. suggest formation state cooling hot first phase, following that, phase leakage formed blobs large transverse material long loops extended away UV top. existence such on sides would avoid really turn around axis.