Hα Doppler shifts in a tornado in the solar corona

Schmieder, B., Mein, P., Mein, N., Levens, P.J., Labrosse, N. and Ofman, L. (2017) Hα Doppler shifts in a tornado in the solar corona. Astronomy and Astrophysics, 597, A109. (doi:10.1051/0004-6361/201628771)

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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 s 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 min. Weaker amplitude oscillations with periods of 4 to 6 min 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.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Labrosse, Dr Nicolas and Levens, Peter
Authors: Schmieder, B., Mein, P., Mein, N., Levens, P.J., Labrosse, N., and Ofman, L.
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Astronomy and Astrophysics
Publisher:EDP Sciences
ISSN:0004-6361
ISSN (Online):1432-0746
Published Online:11 January 2017
Copyright Holders:Copyright © 2017 ESO
First Published:First published in Astronomy and Astrophysics 597: A109
Publisher Policy:Reproduced in accordance with the publisher copyright policy
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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
619541STFC Doctoral Training Grant 2012-17Martin HendryScience & Technology Facilities Council (STFC)ST/K502005/1S&E P&A - PHYSICS & ASTRONOMY
631581Consolidated grant in solar and astrophysical plasmasLyndsay FletcherScience & Technology Facilities Council (STFC)ST/L000741/1S&E P&A - PHYSICS & ASTRONOMY