Observation of a small-scale magnetic vortex associated with a chromospheric swirl: signatures of a small-scale magnetic tornado
Abstract
High-resolution solar observations revealed the existence of small-scale swirling vortices in chromospheric intensity maps and velocity diagnostics. These events are commonly localized in the quiet sun intergranular space and are often related to small-scale magnetic flux concentrations at the solar surface. Frequently, vortices have been observed in the vicinity of magnetic flux concentrations, indicating a link between swirls and the evolution of the small-scale magnetic fields. Vortices were also studied with MHD numerical simulations of the solar atmosphere, revealing their complexity, dynamics, and magnetic nature. In particular, it has been suggested that the chromospheric swirling plasma motion is due to a coherently rotating magnetic field structure, which again is driven by a photospheric vortex flow at its footpoint. In this contribution, we present a comprehensive description of the evolution of an isolated small-scale magnetic element interacting with a vortex flow, which in turn is related to a chromospheric swirl. We study observations taken with the CRisp Imaging SpectroPolarimeter (CRISP) instrument and the CHROMospheric Imaging Spectrometer (CHROMIS) at the 1m Swedish Solar Telescope (SST) in April 2019 as part of a SOLARNET access program. The data were taken at quiet-Sun disk-center, recording full Stokes photospheric maps in the Fe I line at 617 nm, full Stokes data in the Ca II infrared triplet line at 854 nm, and spectroscopic maps in the Hα 656 nm, Ca II K 393 nm, and Ca II H 396 nm lines. Utilizing the multi-wavelength data and applying height-dependent Stokes inversion and local correlation tracking methods, we are able to analyse the magnetic field dynamics in the presence of vortex structures at photospheric and chromospheric layers. The temporal evolution of the magnetic element shows an appreciable increase in the magnetic field strength during the interaction with the vortex flow, reaching kG values for a few minutes. We also find a clear evidence of a Rapid Blue-shift Excursion (RBE) associated with the magnetic field intensification event propagating along the chromospheric vortex. In addition, we explore the polarization signatures in the photosphere to reveal the intrinsic structure of the magnetic element. Marginal but consistent detection of linear polarization signals in the surroundings of the magnetic element before intensification suggests a magnetic field torsion. Our analysis indicates that we have observed a rotating magnetic object reaching from the photosphere to the chromosphere, resembling a small-scale magnetic tornado.
- Publication:
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44th COSPAR Scientific Assembly. Held 16-24 July
- Pub Date:
- July 2022
- Bibcode:
- 2022cosp...44.2521M