We present the new article published in Astronomy and Astrophysics by Y. Taroyan and R. Soler.
Context. Magnetic twists are commonly associated with solar prominences. Twists are believed to play an important role in supporting the dense plasma against gravity as well as in prominence eruptions and coronal mass ejections, which may have a severe impact on the Earth and its near environment.
Aims. We used a simple model to mimic the formation of a prominence thread by plasma condensation with the aim of investigating the possibility of triggering twists during this process.
Methods. Temporal and spatial evolution of torsional Alfvénic perturbations driven by random photospheric motions was analysed using the linearised governing equations of motion and induction.
Results. We find that small amplitude perturbations are exponentially amplified in time as they propagate along the condensing thread. Mechanisms contributing to the rapid growth are explored. The result of the amplification process is the generation of large amplitude axisymmetric twists along the thread.
Conclusions. Magnetic twists may be triggered along a prominence thread when it is permeated by a converging flow, for example, during the evaporation and condensation of plasma along the thread. This may lead to the generation of vortices in the non-linear regime.
Photo: Axially symmetric structure is embedded in corona and rooted in photosphere at both ends. A single magnetic field line representing a thin prominence thread is permeated by inflow U in the longitudinal s-direction. Small-amplitude axisymmetric twists (∂/∂θ) are driven at both footpoints by photospheric motions. The thread is at a distance r from the axis of symmetry.