spicules


spicules

(spik -yoolz) Predominantly vertical narrow (1000-km diameter) jets of gas, visible (in the monochromatic light of certain strong Fraunhofer lines) beyond the Sun's limb. They ascend with velocities of up to 20–30 km s–1 from the lower chromosphere for several thousand kilometers into the inner corona and then fall back and/or fade away. Their average lifetime is 5–10 minutes. They are closely associated with the chromospheric network, being located in regions of enhanced vertical magnetic field at the boundaries of supergranular cells (see supergranulation), and have temperatures of the order of 10 000 to 20 000 K.