Hα Doppler shifts in a tornado in the solar corona

Abstract

Context. High resolution movies in 193 Å from the Atmospheric Imaging Assembly (AIA) on the Solar Dynamic Observatory (SDO) show apparent rotation in the leg of a prominence observed during a coordinated campaign. Such structures are commonly referred to as tornadoes. Time-distance intensity diagrams of the AIA data show the existence of oscillations suggesting that the structure is rotating.Aims. The aim of this paper is to understand if the cool plasma at chromospheric temperatures inside the tornado is rotating around its central axis.Methods. The tornado was also observed in Hα with a cadence of 30 seconds by the MSDP spectrograph, operating at the Solar Tower in Meudon. The MSDP provides sequences of simultaneous spectra in a 2D field of view from which a cube of Doppler velocity maps is retrieved. Results. The Hα Doppler maps show a pattern with alternatively blueshifted and redshifted areas of 5 to 10 wide. Over time the blueshifted areas become redshifted and vice versa, with a quasi-periodicity of 40 to 60 minutes. Weaker amplitude oscillations with periods of 4 to 6 minutes are superimposed onto these large period oscillations. Conclusions. The Doppler pattern observed in Hα cannot be interpreted as rotation of the cool plasma inside the tornado. The Hα velocity observations give strong constraints on the possible interpretations of the AIA tornado.

On the Dynamic Nature of a Quiescent Prominence Observed by IRIS and MSDP Spectrographs

“…The prominence plasma is optically thick in Mg II h and k lines, while it is (approximately) optically thin in The Doppler pattern versus time in Mg II lines as well as in Hα evolves slowly during the 1 hour and half observation time with large cells changing from blue to red. This kind of evolution has been previously observed in a prominence-tornado (Schmieder et al 2017a).…”

“…In the South triangle (region B) a large redshift area is observed at 08:07 UT, the area is decreasing in size and is replaced by blueshift area at 08:38 UT. Such Dopplershift pattern has been observed in other prominences (Schmieder et al 2010(Schmieder et al , 2017a. Long sequences of Dopplershift observations of a prominence-tornado showed such an evolution.…”

Two Solar Tornadoes Observed with the Interface Region Imaging Spectrograph

“…Both observations lasted for more than 2.5 hours, a duration that is long enough to identify possible periodic oscillation (alternation of red and blue shifts) with a ∼1-hour period as identified by Schmieder et al (2017). However, during the whole observations, these adjacent red and blue shifts appear to be persistent, and they do not show any sign change of the Doppler shift.…”

“…Using observations of two tornadoes with the Interface Region Imaging Spectrograph (IRIS, De Pontieu et al 2014), Levens et al (2016a) found no evidence of rotation through an analysis of the Mg ii k Doppler shift. More recently, Schmieder et al (2017) analyzed a solar tornado observed with Hα and found an alternation between redshifted and blueshifted regions, revealing a possible irregular periodicity of about 1 hour. Such behavior is not supposed to be caused by rotation.…”

Prominence Activity during the 2006 Total Solar Eclipse

“…[3] compared the defined features of solar corona at six locations along the track of the total solar ec-Open Access Natural Science lipse 2006; they found that the basic coronal structures were seen in the secured images, moreover, the observed features of solar corona on the processed image is agreement with other processed images from different locations. [4] used high-resolution movies in 193 Å from Atmospheric Imaging Assembly (AIA) on Solar Dynamic Observatory to show apparent rotation of a prominence observed during a coordinated. They found that the Doppler pattern observed in H-Alpha couldn't be interpreted as rotation of the cool plasma inside tornado.…”