UBIQUITOUS TORSIONAL MOTIONS IN TYPE II SPICULES

By Bart De Pontieu, M. Carlsson, L. R. V. Voort, R. Rutten, V. Hansteen, H. Watanabe. 2012

150 citations recorded by the source corpus.

Spicules are long, thin, highly dynamic features that jut out ubiquitously from the solar limb. They dominate the interface between the chromosphere and corona and may provide significant mass and energy to the corona. We use high-quality observations with the Swedish 1 m Solar Telescope to establish that so-called type II spicules are characterized by the simultaneous action of three different types of motion: (1) field-aligned flows of order 50–100 km s−1, (2) swaying motions of order 15–20 km s−1, and (3) torsional motions of order 25–30 km s−1. The first two modes have been studied in detail before, but not the torsional motions. Our analysis of many near-limb and off-limb spectra and narrowband images using multiple spectral lines yields strong evidence that most, if not all, type II spicules undergo large torsional modulation and that these motions, like spicule swaying, represent Alfvénic waves propagating outward at several hundred km s−1. The combined action of the different motions explains the similar morphology of spicule bushes in the outer red and blue wings of chromospheric lines, and needs to be taken into account when interpreting Doppler motions to derive estimates for field-aligned flows in spicules and determining the Alfvénic wave energy in the solar atmosphere. Our results also suggest that large torsional motion is an ingredient in the production of type II spicules and that spicules play an important role in the transport of helicity through the solar atmosphere.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/e82ef5a409cc6e7b2d0301a097b9442d3f4d4070

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In Astronomy and Astrophysics

Citations in the corpus

Coronal Heating by MHD Waves (2020, methodology): “Still, forward modelling of simulations with uniturbulence (Pant et al. 2019) can elegantly and self-consistently explain the observed correlation between wave Doppler shift and spectral line broadening (McIntosh and De Pontieu 2012, as also explained in review of Nakariakov et al. (2020)).”
Multiwavelength Studies of MHD Waves in the Solar Chromosphere (2015, background): “Aside from the transverse displacement of the spicules, evidence for torsional motions in spicules has been provide by De Pontieu et al. (2012).”
The Interface Region Imaging Spectrograph (IRIS) (2012, background): “…the chromosphere and corona (Tomczyk et al., 2007; De Pontieu et al., 2007a; Tomczyk and McIntosh, 2009; McIntosh et al., 2011; Liu et al., 2011; De Pontieu et al., 2012; Wedemeyer-Böhm et al., 2012; Su et al., 2013; Verwichte et al., 2013), but it is unclear what role higher frequency waves…”
Solar Fine-Scale Structures. I. Spicules and Other Small-Scale, Jet-Like Events at the Chromospheric Level: Observations and Physical Parameters (2012, methodology): “Recently, De Pontieu et al. (2012) using high-quality observations from SST provided evidence that most, if not all, Type II spicules are characterized by the simultaneous action of three different types of motion: (1) field-aligned flows of order 50 – 100 km s−1, (2) swaying motions of order 15 –…”
CRISPRED: A data pipeline for the CRISP imaging spectropolarimeter (2014, background): “…of a relatively large field-of-view (FOV) with very high cadence, very high spatial resolution, and an acceptable wavelength coverage (e.g., Tritschler et al. 2004; Cauzzi et al. 2008; Bello González & Kneer 2008; Scharmer et al. 2008; Steiner et al. 2010; De Pontieu et al. 2012, among others).”