Unveiling the magnetic nature of chromospheric vortices

Abstract

Context. Vortex structures in the Sun's chromosphere are believed to channel energy between different layers of the solar atmosphere. <BR /> Aims: We investigate the nature and dynamics of two small-scale quiet-Sun rotating structures in the chromosphere. <BR /> Methods: We analysed two chromospheric structures that show clear rotational patterns in spectropolarimetric observations taken with the Interferometric Bidimensional Spectrometer at the Ca II 8542 Å line. <BR /> Results: We present the detection of spectropolarimetric signals that manifest the magnetic nature of rotating structures in the chromosphere. Our observations show two long-lived structures of plasma that each rotate clockwise inside a 10 arcsec<SUP>2</SUP> quiet-Sun region. Their circular polarisation signals are five to ten times above the noise level. Line-of-sight Doppler velocity and horizontal velocity maps from the observations reveal clear plasma flows at and around the two structures. A magnetohydrodynamics simulation shows these two structures are plausibly magnetically connected. Wave analysis suggests that the observed rotational vortex pattern could be due to a combination of slow actual rotation and a faster azimuthal phase speed pattern of a magnetoacoustic mode. <BR /> Conclusions: Our results imply that the vortex structures observed in the Sun's chromosphere are magnetic in nature and that they can be connected locally through the chromosphere <P />Movies are available at <A href="https://www.aanda.org/10.1051/0004-6361/202038360/olm">https://www.aanda.org</A>