Imaged by atmospheric optics expert Peter-Paul Hattinga Verschure at Deventer in The Netherlands on 11th September. The Bishop's ring was likely produced by Californian wildfire smoke.?The Bishop’s ring is the centre part of a huge corona. An aureole edged with brownish yellow and reds. Tiny particles ~1 micron or so in size diffract sunlight to produce it.?The source of the particle producing this one? Wildfire smoke from the US West Coast. Satellite imagery detected the smoke carried easterly across the US and Atlantic Ocean. ?Small smoke particles are ideal candidates to generate Bishop’s rings. Particles from volcanic eruptions and desert sand make them too.?
Smoke over Europe on 11th September 2020.
An opaque particle diffracts an incoming plane light wave. All points on the particle's surface are sources of outgoing spherical waves of scattered light. The spherical waves overlap and interfere. There is brightness where their electric vectors are of the same sign and zero intensity where they are of opposite sign and cancel.?The result in the forward direction is a corona or, for very small particles, a Bishop's ring.