Definitions

irregular, luminous phenomena, as streamers, visible at night in a zone surrounding the north magnetic pole and produced in the ionosphere when atomic particles strike and excite atoms; northern lights.

Belgium, Netherlands and Luxembourg.

colored rings around shadows projected against fog or cloud droplets.

solar and lunar coronas consist of a series of rainbow-colored rings around the sun or moon. Such coronas resemble halos but differ in having a reverse sequence of the spectrum colors, red being the color of the outer ring, and in having smaller and variable radii. This reversed sequence of the spectrum occurs because coronas result from diffraction of light whereas the halo is a refraction phenomenon.

narrow inlet or arm of the sea bordered by steep cliffs.

the green flash is caused by refractive separation of the sun’s rays into its spectral components. This may occur at sunrise or sunset when only a small rim of the sun is visible. When refractive conditions are suitable, red, orange, and yellow waves of sunlight are not refracted sufficiently to reach the eye whereas green waves are. The visual result is a green flash in the surrounding sky.

a ring of light that seems to encircle the sun, moon, or other luminous bodies. It results from the refraction of light through ice crystals in the atmosphere.

are reflection phenomena observed on the underside of cloud surfaces.

a mirage is caused by refraction of light rays in a layer of air having rapidly increasing or decreasing density near the surface. A marked decrease in the density of the air with increasing altitude is the cause of such phenomena known as looming, towering and superior mirages. Looming is said to occur when objects appear to rise above their true elevation. Objects below the horizon may actually be brought into view. Towering has the effect of elongating the visible objects in the vertical direction. A superior mirage is so named because of the appearance of an image above the actual object. The inferior mirage is due to increasing air density with height. Atmospheric zones of varying densities and thickness’ may combine the effects of the various types of mirages to form a complicated mirage system known as Fata Morgana.

the refraction of light by ice crystals. Because red light is refracted the least, the inner ring of this arc is always red with the other colors of the spectrum following outward.

the "fire" appears as a bluish luminous brush discharge of electricity and is most likely to be seen leaping from ships’ masts and spars. St. Elmo’s fire is also known as Corposan, from Corpo Santo, or ghost because of its once supposed supernatural nature.