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Creators/Authors contains: "Verwichte, Erwin"

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  1. ABSTRACT We present the first observations of chromospheric swirls using the Hydrogen-alpha Rapid Dynamics camera and Rapid Oscillations in the Solar Atmosphere imaging instruments at the Dunn Solar Telescope. These vortices contribute to heating and dynamics across the solar atmosphere. We analyse the morphology and evolution of 34 swirls and their cospatial bright points (BPs) from the photosphere to the mid-chromosphere. To examine swirl–BP interactions and temporal behaviour, we use image segmentation, Fourier and spectral analysis, and local correlation tracking. The observed swirls have an average lifetime of 7.9 $$\pm$$ 5 min and diameter of 3.6 $$\pm$$ 1 Mm, with a positive correlation indicating smaller swirls tend to be short-lived. 76 per cent are associated with a compact BP appearing 12 s to 9 min after swirl formation. Swirl motion is also closely linked to their BP(s) global motions. The swirls exhibit a mean angular speed of 0.04 rad s$$^{-1}$$, radial speed of 17.7 km s$$^{-1}$$, and period of 180 s. We observe the formation of a spiral-shaped swirl driven by a BP interacting with a large photospheric vortex. The BP is dragged towards the vortex centre, after which the swirl forms. The BP undergoes changes in orientation and elongation that mirror the swirl’s chromospheric development. A time lag of $-42.5$ s between the sudden change in the BP’s orientation and the peak of the swirl’s intensity variation suggests torsional Alfvén waves may contribute to swirl evolution. Our results support a magnetic origin for swirls rooted in motions of photospheric BPs. 
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  2. Abstract We investigate high-resolution spectroscopic and imaging observations from the CRisp Imaging SpectroPolarimeter (CRISP) instrument to study the dynamics of chromospheric spicule-type events. It is widely accepted that chromospheric fine structures are waveguides for several types of magnetohydrodynamic (MHD) oscillations, which can transport energy from the lower to upper layers of the Sun. We provide a statistical study of 30 high-frequency waves associated with spicule-type events. These high-frequency oscillations have two components of transverse motions: the plane-of-sky (POS) motion and the line-of-sight (LOS) motion. We focus on single isolated spicules and track the POS using time–distance analysis and in the LOS direction using Doppler information. We use moment analysis to find the relation between the two motions. The composition of these two motions suggests that the wave has a helical structure. The oscillations do not have phase differences between points along the structure. This may be the result of the oscillation being a standing mode, or that propagation is mostly in the perpendicular direction. There is evidence of fast magnetoacoustic wave fronts propagating across these structures. To conclude, we hypothesize that the compression and rarefaction of passing magnetoacoustic waves may influence the appearance of spicule-type events, not only by contributing to moving them in and out of the wing of the spectral line but also through the creation of density enhancements and an increase in opacity in the Hαline. 
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