Below Horizon Halos Imaged by Tim Stone (images) over Tennessee. ©Tim Stone, shown with permission. All these halos are below the horizon, formed by ice crystals in clouds beneath the aircraft. The familiar 22° halo curves across the image. Touching it is a narrow lower tangent arc produced by horizontal column crystals. The LTA's wings point down to join a subsun mirrored by plate crystals. The HaloSim ray tracing simulation is for a sun elevation of 15°.    Tangent arcs  Subsun   HaloSim