spicule
- A spike of ice formed during the freezing of a water drop or a contained volume of water (as in a puddle or freezer container); expansion of the inward freezing ice expels any remaining water through a weak point in the shell which then freezes as a spike in the colder environment.
- Rapidly changing, predominantly vertical spike-like structures in the solar chromosphere and observed extending from the solar limb. Spicules appear to be ejected from the low chromosphere at velocities of 20–30 km s−1 and can reach heights of 9000 km before falling back or fading. Their total lifetime generally spans 5–10 minutes.
Term edited 10 September 2018.
