Rare Sightings of Halo and Arcs Captured Three Solar Phenomena Caused by Ice Crystals

In Belfast, Northern Ireland, photographs of an unusual solar phenomenon were captured on May 28 by astronomer Alan Fitzsimmons. The event, displayed in the Botanic Gardens, lasted about 30 minutes. The lacelike network of ethereal halos and light arcs was also observed in some parts of Northern Ireland, Scotland, and northern England.

A Look at the Ultra-Rare Phenomena

The images captured by Fitzsimmons show three confirmed optical phenomena created separately. The large circle surrounding the sun is a 22-degree shining halo produced when light beams enter one side of the columnar ice crystals and pass through the other. The ethereal halo also comes with sundogs or colored weak spots on one or both sides of the sun. Lastly, the circle was bisected by a horizontal white band known as a parhelic circle, which appears when the light from the sun is reflected near the vertical sides of ice crystals.

The complete parhelic circle is the rarest and most impressive among these three solar phenomena that appeared simultaneously. This is because millions of ice crystals catching sunbeams simultaneously need at least five internal reflections. The two other solar phenomena are more common than most people realize.

Depending on the observer's location, the event may include sightings of circumscribed halo in addition to a supralateral arc. Together, they may form the "eyelids" seen above and below the 22-degree halo.

Each of the optical phenomena was created by the refraction of light through millions of ice crystals in perfect alignment in the upper atmosphere, often accompanying thin cirrus clouds. According to Fitzsimmons, the alignment of hexagonal-shaped crystals happens due to uniform winds in the upper atmosphere. Like a prism, the crystals refract the sunlight and allow the passing beams to combine, creating light arcs and circles.

By the time the phenomena are visible, the sun can be too bright, so it must be blocked with a thumb or a tree to notice the event. Fitzsimmons also added that it is worth looking if a halo is present or if there are other solar phenomena when it is sunny with delicate clouds at high altitudes.

Other Sightings of Solar Phenomena

Various sun-related phenomena can be observed due to light obstruction by tiny atmospheric ice crystals and other particles suspended in the air.

On May 30, a photographer captured eye-catching images of shining rainbow rings surrounding the sun near his home in Turku City, Finland. This bizarre event is called pollen coronas which was caused by the refraction of sunlight by pine tree pollens floating in the air.

On a separate occasion, rare rainbow clouds were seen across several locations in the Arctic Circle in February. These multi-colored lights, called polar stratospheric clouds (PSCs), were formed by entering water vapor in the stratosphere, which later condenses due to cold temperatures.

Another rare cloud formation is expected in the Northern Hemisphere in June and July. In this season, the northern skies will be filled with colored streaks of noctilucent clouds, which are also called night-shining clouds. They are formed when light is reflected by the water vapor in the air that gets frozen into ice crystals and clings to dust left by falling meteors.