PREDNASAJUCI / LECTURER : 

Jan Rybak

NAZOV / TITLE : 

Cold plasma rotation in the tornado-like prominence of July 13, 2014:
a real motion or an illusive effect?

ABSTRAKT / ABSTRACT : 

In this case study we analyze the tornado-like prominence of July 13, 2014
which shows changing position in the SDO/AIA imaging at EUV wavelengths.
We use the H alpha 2D spectroscopy data acquired with the CoMP-S instrument
(Lomnicky Stit Observatory - LSO, AISAS, Slovakia) and the Mg II h 1D
spectroscopy data from the IRIS satellite. The aim of the study is to
address the question whether this structure is a real tornado (prominence
leg plasma rotating around central axis) or we just observe illusive
signatures of an apparent rotational motion, like oscillation.
Our case study results indicate that: a/ the detected Doppler shifts
do not show a permanent blue/red-shift pattern along the vertical axis
of the structure during the whole observing time intervals of the
CoMP-S and IRIS instruments (45 and 25  min, resp.), b/ the present
variations of the Doppler shifts (± 4 km/s and ± 15 km/s for the
CoMP-S H alpha line and IRIS Mg II h line, resp.) are not in general clearly
correlated with the H alpha and Mg II h integral line emissions of the structure,
c/ the Doppler shift variations do not show any regular oscillatory behavior.
These results lead to conclusion that the Doppler shifts of this particular
tornado-like structure cannot be interpreted as real cold plasma rotation
around the vertical axis of the structure. However the purely imaging
SDO/AIA observations show clear illusive vortical motions in this
tornado-like structure. We suggest that the 'vortical illusion'
(Panasenco et al., 2014) - a combination of the counter-streaming
flows in the prominence threads and possible radiative transfer effects -
are causing the apparent rotational motion of this tornado-like structure.