DYNAMICS OF A SOLAR PROMINENCE TORNADO OBSERVED BYSDO/AIA ON 2012 NOVEMBER 7–8

Abstract

We study the detailed dynamics of a solar prominence tornado using time series of 171, 304, 193 and 211Å spectral lines obtained by Solar Dynamics Observatory/ Atmospheric Imaging Assembly during 2012 November 7-8. The tornado first appeared at 08:00 UT, November 07, near the surface, gradually rose upwards with the mean speed of ∼ 1.5 km s −1 and persisted over 30 hr. Timedistance plots show two patterns of quasi-periodic transverse displacements of the tornado axis with periods of 40 and 50 minute at different phases of the tornado evolution. The first pattern occurred during the rising phase and can be explained by the upward motion of the twisted tornado. The second pattern occurred during the later stage of evolution when the tornado already stopped rising and could be caused either by MHD kink waves in the tornado or by the rotation of two tornado threads around a common axis. The later hypothesis is supported by the fact that the tornado sometimes showed a double structure during the quasi-periodic phase. 211 and 193Å spectral lines show a coronal cavity above the prominence/tornado, which started expansion at ∼ 13:00 UT and continuously rose above the solar limb. The tornado finally became unstable and erupted together with the corresponding prominence as coronal mass ejection (CME) at 15:00 UT, November 08. The final stage of the evolution of the cavity and the tornado-related prominence resembles the magnetic breakout model. On the other hand, the kink instability may destabilize the twisted tornado, and consequently prominence tornadoes can be used as precursors for CMEs.

Hα Doppler shifts in a tornado in the solar corona

“…A mean period of 90 minutes is a reasonable value. The tornado looks as if it is a double structure at the top, which is similar to that seen in Mghebrishvili et al (2015). According to the amplitude of the oscillations, we estimate a velocity of 7 km s −1 .…”

“…The Hα velocity behaviour gives some constraints on the models proposed to interpret the rotation of AIA tornadoes. A first scenario could be to interpret the quasi-periodic pattern observed by AIA as being due to kink oscillations such as in Mghebrishvili et al (2015). Such a scenario leads those authors to derive some physical characteristics of their tornado.…”

On the Magnetism and Dynamics of Prominence Legs Hosting Tornadoes

“…Fibrils that move with respect to each other have already been reported and interpreted as rotation around a common axis (Mghebrishvili et al 2015). In our case, this is unlikely because the structures would take several hours to perform a turn, while the Doppler patterns change in less than one hour.…”

“…Different periods in height mean that the different heights of the prominence are out of phase and the resulting zig-zag motion resembles the observed SDO/AIA tornadoes. Mghebrishvili et al (2015) also reported the detection of quasi- periodic transverse displacements, interpreted as MHD kink waves, in a solar prominence tornado. Their time distance analysis showed two patterns of quasi-periodic brightness displacements with periods of about 40 and 50 minutes.…”

“…Solar tornadoes are nowadays associated with the vertical funnel-shaped dark structures seen in the coronal Fe IX line at 17.1 nm. These structures are found to be hosted in the legs of some quiescent prominences (e.g., Su et al 2012;Wedemeyer et al 2013) and seem to be directly linked to the evolution and final fate of the prominence (Li et al 2012;Mghebrishvili et al 2015).…”