Recently, it was shown that the complex dynamical behaviour of spicules has to be interpreted as the result of simultaneous action of three kinds of motion: (1) field aligned flows, (2) swaying motions, and (3) torsional motions. We use high-quality observations from the CRisp Imaging SpectroPolarimeter at the Swedish 1-meter Solar Telescope to investigate signs of these different kinetic modes in spicules on the disk. Earlier, rapid blue-shifted excursions (RBEs), short-lived absorption features in the blue wing of chromospheric spectral lines, were identified as the disk counterpart of type II spicules. Here we report the existence of similar absorption features in the red wing of the Ca II 8542 and Hα lines: rapid red-shifted excursions (RREs). RREs are found over the whole solar disk and are located in the same regions as RBEs: in the vicinity of magnetic field concentrations. RREs have similar characteristics as RBEs: they have similar lengths, widths, lifetimes, and average Doppler velocity. The striking similarity of RREs to RBEs implies that RREs are a manifestation of the same physical phenomenon and that spicules harbour motions that can result in a net red-shift when observed on-disk. We find that RREs are less abundant than RBEs: the RRE/RBE detection count ratio is about 0.52 at disk center and 0.74 near the limb. We interpret the higher number of RBEs and the decreased imbalance towards the limb as an indication that field-aligned up-flows have a significant contribution to the net Dopplershift of the structure. Most RREs and RBEs are observed in isolation but we find many examples of parallel and touching RRE/RBE pairs which appear to be part of the same spicule. We interpret the existence of these RRE/RBE pairs and the observation that many RREs and RBEs have varying Dopplershift along their width as signs that torsional motion is an important characteristic of spicules. The fact that most RBEs and RREs are observed in isolation agrees with the idea that transversal swaying motion is another important kinetic mode. We find examples of transitions from RRE to RBE and vice versa. These transitions sometimes appear to propagate along the structure with speeds between 18 and 108 km s −1 and can be interpreted as the sign of a transverse (Alfvénic) wave.

Spicules were recently found to exist as two different types when a new class of so-called type II spicules was discovered at the solar limb with the Solar Optical Telescope on board the Hinode spacecraft. These type II spicules have been linked with on-disk observations of rapid blueshifted excursions (RBEs) in the Hα and Ca ii 8542 lines. Here we analyze observations optimized for the detection of RBEs in both Hα and Ca ii 8542 lines simultaneously at a high temporal cadence taken with the Crisp Imaging Spectropolarimeter at the Swedish Solar Telescope on La Palma. In this study, we used a high-quality time sequence for RBEs at different blueshifts and employed an automated detection routine to detect a large number of RBEs in order to expand on the statistics of RBEs. We find that the number of detected RBEs is strongly dependent on the associated Doppler velocity of the images on which the search is performed. Automatic detection of RBEs at lower velocities increases the estimated number of RBEs to the same order of magnitude expected from limb spicules. This shows that RBEs and type II spicules are indeed exponents of the same phenomenon. Furthermore, we provide solid evidence that Ca ii 8542 RBEs are connected to Hα RBEs and are located closer to the network regions with the Hα RBEs being a continuation of the Ca ii 8542 RBEs. Our results show that RBEs have an average lifetime of 83.9 s when observed in both spectral lines and that the Doppler velocities of RBEs range from 10 to 25 km s −1 in Ca ii 8542 and 30 to 50 km s −1 in Hα. In addition, we automatically determine the transverse motion of a much larger sample of RBEs than previous studies, and find that, just like type II spicules, RBEs undergo significant transverse motions of the order of 5-10 km s −1 . Finally, we find that the intergranular jets discovered at Big Bear Solar Observatory are a subset of RBEs.

The newly established type II spicule has been speculated to provide enough hot plasma to play an important role in the mass loading and heating of the solar corona. With the identification of Rapid Blueshifted Excursions (RBEs) as the on-disc counterpart of type II spicules we have analysed three different high quality timeseries with the CRisp Imaging SpectroPolarimeter (CRISP) at the Swedish Solar Telescope (SST) on La Palma and subjected to an automated detection routine to detect a large number of RBEs for statistical purposes. Our observations are of a quiet Sun region at disc centre and we find lower Doppler velocities, 15-40 km s −1 , and Doppler widths, 2-15 km s −1 , of RBEs than in earlier coronal hole studies, 30-50 km s −1 and 7-23 km s −1 , respectively. In addition, we examine the spatial dependence of Doppler velocities and widths along the RBE axis and conclude that there is no clear trend to this over the FOV or in individual RBEs in quiet Sun at disc centre. These differences with previous coronal hole studies are attributed to the more varying magnetic field configuration in quiet Sun conditions. Using an extremely high cadence dataset has allowed us to improve greatly on the determination of lifetimes of RBEs, which we find to range from 5 to 60 s with an average lifetime of 30 s, as well as the transverse motions in RBEs, with transverse velocities up to 55 km s −1 and averaging 12 km s −1 . Furthermore, our measurements of the recurrence rates of RBEs provide important new constraints on coronal heating by spicules. We also see many examples of a sinusoidal wave pattern in the transverse motion of RBEs with periods averaging 54 s and amplitudes from 21.5 to 129 km which agrees well with previous studies of wave motion in spicules at the limb. We interpret the appearance of RBEs over their full length within a few seconds as the result of a combination of three kinds of motions as is earlier reported for spicules. Finally, we look at the temporal connection between Hα and Ca II 8542 RBEs and find that Ca II 8542 RBEs in addition to being located closer to the footpoint also appear before the Hα RBEs. This connection between Ca II 8542 and Hα supports the idea that heating is occurring in spicules and contribute more weight to the prominence of spicules as a source for heating and mass loading of the corona.