A spike-like jet of dense plasma in the upper chromosphere of the Sun, visible especially in Ηα‎ light. Spicules rise upwards towards the corona at velocities of about 30 km/s, reaching altitudes of 9000 km in about 90 s. They last about 15 min, ending their lives by fading rather than descending. They tend to be clustered, giving the appearance of porcupine quills on the solar limb. Seen against the disk, in Ηα‎ light, they seem to be identifiable as fine mottles, light or dark depending on their height (although they always appear dark when observed in the red line wing of the Ηα‎ line). Spicules are seen at the edges of the chromospheric network where the magnetic field is strongest. Fine mottles form clusters with their bases in the coarse mottles which outline the chromospheric network. At the centre of the Sun’s disk, clumps of spicules form radiating patterns sometimes called rosettes.