Natural phenomena

PARHELIA
Group of optical phenomena, in the form of rings, arcs, pillars or bright spots around the Sun or Moon, produced by the interaction of light with ice crystals suspended in the atmosphere. When a thin uniform cirrostratus cloud deck containing ice crystals covers the sky, the halo may be in the form of a complete circle. There are many types of halos. One of special note is the “sun dog.” Sun dogs are luminous spots on both sides of the sun that occasionally occur with a halo.

AURORA
Luminous phenomena, in the form of arcs, bands, draperies, or curtains in the high atmosphere over high latitudes. Auroras are related to magnetic storms and the influx of charged particles from the Sun. The phenomena are called aurora borealis in the Northern Hemisphere and aurora australis in the Southern Hemisphere. the spectacular color displays of the aurora borealis appear on clear, cold nights in the arctic sky during periods of solar activity. The height of the auroras is about 70 km to 200 km above the earth’s surface. The amazing color displays and formations are produced by the solar wind, a stream of electrons and protons coming from the sun, as it collides with oxygen and nitrogen atoms in the upper atmosphere. High-altitude oxygen, about 200 km up, produces rare, all-red auroras, while lower-altitude oxygen, about 60 km up, is the source of the most common auroral color, a bright yellow-green. Blue light comes from ionized nitrogen molecules. The nitrogens also create purplish-red and red colors in the aurora. Although auroras are now reasonably well understood, aspect of them continue to intrigue scientists.

POLAR  NIGHT
In polar regions, the portion of the year when the Sun does not rise above the horizon. Its length changes from twenty hours at the Arctic/Antarctic Circle (latitude 66°33′ N or S) to 179 days at the North/South Pole.

ICE  BLINK
Ice blink refers to a white glare seen on the underside of low clouds indicating the presence of ice which may be beyond the range of vision. When other means of reconnaissance are not available, ice blink can assist travelers in navigating the ice of the polar seas, since give a rough idea of ice conditions at a distance.

WATER  SKY
Are the opposite of ice blinks and occur when dark patches of open water cause dark streaks on the clouds. Like the ice blink can assist the navigation in the polar seas.

WHITEOUT
It occur when heavy clouds diffuse the sunlight over the snow covered ground in blizzard conditions. Then distance measurement become almost impossible and loss of orientation is common.

FATA  MORGANA
The fata morgana is a complex mirage in which distant objects are distorted as well as elongated vertically. For example, a relatively flat shoreline may appear to have tall cliffs, columns, and pedestals. The phenomenon is caused by the distortions in the path of light from distant objects to the observer as a result of the light traveling through layers of air at different temperatures and densities.