Statistical properties of the Disk Counterparts of Type II Spicules from simultaneous observations of RBEs in Ca II 8542 and H{\alpha}

TL;DR

This study analyzes the statistical properties of RBEs in Ca II 8542 and Hα lines, demonstrating their connection to type II spicules, and provides detailed measurements of their dynamics and lifetimes.

Contribution

It offers the first comprehensive statistical analysis of RBEs in both spectral lines simultaneously, linking them to type II spicules and detailing their motion and lifetime characteristics.

Findings

RBEs are more numerous at lower Doppler velocities.

Ca II 8542 RBEs are connected to Hα RBEs and located near network regions.

RBEs have an average lifetime of about 84 seconds and transverse motions of 5-10 km/s.

Abstract

Spicules were recently found to exist as two types when a new class of so-called type II spicules was discovered at the solar limb with Hinode. The type II spicules have been linked with on-disk observations of Rapid Blue-shifted Excursions (RBEs) in the Ha and Ca 8542 lines. Here we analyze observations optimized for the detection of RBEs in both Ha and Ca 8542 simultaneously at a high temporal cadence taken with CRISP at the SST. This study used a high-quality time sequence for RBEs at different blue-shifts 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 dependent on the Doppler velocity of the images on which the search is performed. 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 exponents of the same phenomenon. We provide evidence that Ca 8542 RBEs are connected to Ha RBEs and are located closer to the network regions with the Ha RBEs being the continuation, and show that RBEs have an average lifetime of 83.9 s when observed in both spectral lines with Doppler velocity ranges of 10-25 km/s in Ca 8542 and 30-50 km/s in Ha. In addition, we determine the transverse motion of a much larger sample of RBEs than previous studies and find that like type II spicules, RBEs undergo significant transverse motions, 5-10 km/s. Finally, we find that the intergranular jets discovered in BBSO are a subset of RBEs.