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

Abstract

Context. The dynamical nature of fine structures in prominences remains an open issue, including rotating flows in tornado prominences. While the Atmospheric Imaging Assembly imager aboard the Solar Dynamics Observatory allowed us to follow the global structure of a tornado-like prominence for five hours, the Interface Region Imaging Spectrograph, and the Multichannel Subtractive Double Pass spectrograph permitted to obtain plasma diagnostics of its fine structures. Aims. We aim to address two questions. Firstly, is the observed plasma rotation conceptually acceptable in a flux rope magnetic support configuration with dips? Secondly, how is the plasma density distributed in the tornado-like prominence? Methods. We calculated line-of-sight velocities and non-thermal line widths using Gaussian fitting for Mg II lines and the bisector method for Hα line. We determined the electron density from Mg II line integrated intensities and profile fitting methods using 1D non-LTE radiative transfer theory models. Results. The global structure of the prominence observed in Hα, and Mg II h, and k line fits with a magnetic field structure configuration with dips. Coherent Doppler shifts in redshifted and blueshifted areas observed in both lines were detected along rapidly-changing vertical and horizontal structures. However, the tornado at the top of the prominence consists of multiple fine threads with opposite flows, suggesting counter-streaming flows rather than rotation. Surprisingly we found that the electron density at the top of the prominence could be larger (1011 cm−3) than in the inner part of the prominence. Conclusions. We suggest that the tornado is in a formation state with cooling of hot plasma in a first phase, and following that, a phase of leakage of the formed blobs with large transverse flows of material along long loops extended away from the UV prominence top. The existence of such long magnetic field lines on both sides of the prominence would stop the tornado-like prominence from really turning around its axis.

First high resolution interferometric observation of a solar prominence with ALMA

“…The small prominence appearing abo v e the south-west solar limb on 2018 April 19 was well observed by ALMA together with other ground-based and space-based observatories. Peat et al ( 2021 ) carried out a detailed analysis of its emission in the Mg II h and k lines observed by the IRIS spacecraft, while Barczynski et al ( 2021 ) investigated its dynamics in relation to its magnetic structure. Heinzel et al ( 2022 ) studied the effect of the filling factor on the relation between brightness and kinetic temperatures.…”

The Stationary Electric Field in the Heliosphere and Its Possible Relation to Current Sheets

“…For example, Alfvén [31] was able to account for double layers in the solar atmosphere when describing the heliospheric current circuit (he directly used the electric potentials, not Ω). Another example is that large magnetic vortices are possible in the solar atmosphere-the motion of plasma that resembles terrestrial tornadoes [32,33]. In this case, the plasma's rotation around the axis of the vortex can be much faster than around the axis of the Sun.…”

First High Resolution Interferometric Observation of a Solar Prominence With ALMA

“…The small prominence appearing above the south-west solar limb on 19th April 2018 was well observed by ALMA together with other ground-based and space-based observatories. Peat et al (2021) carried out a detailed analysis of its emission in the Mg II h and k lines observed by the IRIS spacecraft, while Barczynski et al (2021) investigated its dynamics in relation to its magnetic structure.…”