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 H \alpha 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 H \alpha RBEs .
This connection between Ca II 8542 and H \alpha 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 .