Rays passing through horizontally aligned column ice crystals form tangent arcs. Their lower tip is always 22 degrees from the sun and touches the 22 degree circular halo when the latter is present.

Tangent arc shapes change dramatically as the sun climbs. At low sun they are V shaped. As the sun climbs the V opens up until eventually the arc resembles a gull's wings. Eventually the upper tangent arc joins its lower counterpart to form a circumscribed halo.

Tangent arcs are coloured. This one shows only the sun's highly reddened hues.