24°-Lateralbögen (EE70)

At the 24° ring, depending on the sun's altitude, up to four white light enhancements can occur. These lateral arcs are located at the upper and lower right and left areas of the 24° ring. In the image, the upper left 24° lateral arc is visible as a weak brightening of the 24° ring. Only with crystals that have an almost ideally horizontally oriented main axis can the arc shape of this halo type also be seen, with the lateral arcs slightly bending away from the 24° ring (see also the simulation). The upper two lateral arcs become very faint at a sun altitude of more than 30° and cannot form at even higher sun positions. The lower two lateral arcs, on the other hand, can occur up to a sun altitude of about 60°, at which point they move away from the 24° ring.

The 24° lateral arcs are formed in pyramidal crystals with vertically oriented principal axis. The principal axis goes through the two base surfaces. Observations show that pyramidal crystals do not align as precisely as plate or columnar crystals. Most of the time, the tilt angles are more than 10°. In contrast, plate and columnar crystals often exhibit tilt angles of less than one degree.