We analyze ground-based chromospheric data acquired at a high temporal cadence of 2 s in wings of the Hα spectral line using Goode Solar Telescope (GST) operating at the Big Bear Solar Observatory. We inspected a 30 minute long Hα-0.08~nm data set to find that rapid blue-shifted Hα excursions (RBEs), which are a cool component of type II spicules, experience very rapid morphological changes on the time scales of the order of 1 second. Unlike typical reconnection jets, RBEs very frequently appear \textit{in situ} without any clear evidence of Hα material being injected from below. Their evolution includes inverted "Y", "V", "N", and parallel splitting (doubling) patterns as well as sudden formation of a diffuse region followed by branching. We also find that the same feature may undergo several splitting episodes within about 1 min time interval.
@article{arxiv.2005.04253,
title = {Rapid Evolution of Type II Spicules Observed in Goode Solar Telescope On-Disk H-alpha Images},
author = {Vasyl Yurchyshyn and Wenda Cao and Valentina Abramenko and Xu Yang and Kyung-Suk Cho},
journal= {arXiv preprint arXiv:2005.04253},
year = {2020}
}