Abstract
Abstract Understanding the dynamic behavior of spicules, e.g., in terms of magnetohydrodynamic (MHD) wave mode(s), is key to unveiling their role in energy and mass transfer from the photosphere to corona. The transverse, torsional, and field-aligned motions of spicules have previously been observed in imaging spectroscopy and analyzed separately for embedded wave-mode identification. Similarities in the Doppler signatures of spicular structures for both kink and torsional Alfvén wave modes have led to the misinterpretation of the dominant wave mode in these structures and is a subject of debate. Here, we aim to combine line- of-sight (LOS) and plane-of-sky (POS) velocity components using the high spatial/temporal resolution Hα imaging-spectroscopy data from the CRisp Imaging SpectroPolarimeter based at the Swedish Solar Telescope to achieve better insight into the underlying nature of these motions as a whole. The resultant three-dimensional velocity vectors and the other derived quantities (e.g., magnetic pressure perturbations) are used to identify the MHD wave mode(s) responsible for the observed spicule motion. We find a number of independent examples where the bulk transverse motion of the spicule is dominant either in the POS or along the LOS. It is shown that the counterstreaming action of the displaced external plasma due to spicular bulk transverse motion has a similar Doppler profile to that of the m = 0 torsional Alfvén wave when this motion is predominantly perpendicular to the LOS. Furthermore, the inferred magnetic pressure perturbations support the kink wave interpretation of observed spicular bulk transverse motion rather than any purely incompressible MHD wave mode, e.g., the m = 0 torsional Alfvén wave.
Highlights
One of the major problems in solar physics today is identifying the energy transfer mechanisms throughout the chromosphere and transition region
There are no direct methods to estimate the errors associated with these velocity measurements, for the interested reader, the uncertainties associated with the input region of interest (ROI) for the Fourier Local Correlation Tracking algorithm (FLCT) algorithm are discussed in detail in the appendix to Freed et al (2016)
To gain a better insight into the true nature of 3D spicular motion from observations, it is crucial to carefully analyze the line of sight (LOS) and POS velocity components and how they relate to each other. We have achieved this by combining both imaging and spectroscopic Hα data from the high spatial temporal resolution CRisp Imaging SpectroPolarimeter (CRISP) instrument
Summary
One of the major problems in solar physics today is identifying the energy transfer mechanisms throughout the chromosphere and transition region. A key observational “window” into this problem is the study of spicules, which are thin, long, jet-like magnetic features that populate the highly dynamic and complex region between the solar photosphere and corona. These enigmatic structures are observed in chromospheric spectral lines such as Hα, Ca II H and K, and He I D3 from both ground- and space-based instrumentation and are a focus of wave physics in the solar chromosphere (Zaqarashvili & Erdélyi 2009; Jess et al 2015; Verth & Jess 2016). This makes it challenging to decipher the true motions of spicules and to identify the possible presence of magnetohydrodynamic (MHD) wave modes
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call