2016 Mar

Physics of Sky Phenomena

March 13, 2016

Physics of Light Pillars

There are many light related phenomena in the sky, beyond those that we have learnt during our Physics tuition classes, such as Light Pillars, Parhelic circles, Zodiacal light and Auroras, just to mention a few. Let’s look at these events in more detail!

Light pillars are an optical wonder where segments of light are seen exuding from underneath or over a source of light. Light pillars appear when artificial, or natural light reflects on flat ice crystal stones in the air near the surface of the earth. Light pillars produced by the Sun are known as Sun or Solar pillars while those brought about by the light from the moon are known as Moon or Lunar pillars.

Parhelic circles are white round groups in the sky at the same level as the Moon or Sun. Essentially, the circles can be sometimes seen partially. They are created when vertical crystals of ice, of any shape reflect daylight or moonlight.

Zodiacal light is a weak, generally triangular, diffuse white glow found in the night sky that seems to reach out up from the region of the Sun along the zodiac or ecliptic. It is best seen soon after dusk in spring, and just before dawn in autumn, when the zodiac is at a lofty point to the horizon. Brought on by daylight scattered by space dust in the zodiacal cloud, it is faint to the point that either moonlight or light contamination renders it undetectable. The zodiacal light declines in intensity with separation from the Sun, yet on exceptionally dim evenings it has been seen in a band totally around the ecliptic. Indeed, the zodiacal light covers the whole sky, being responsible in substantial part for the aggregate bay window on a moonless night.

An aurora, from time to time called a polar light, is a normal light show in the sky, commonly seen in the Arctic and Antarctic. Auroras are formed when the magnetosphere is adequately aggravated by the sun powered wind that the directions of excited particles in both sunlight based wind and magnetospheric plasma, principally as electrons and protons, push them into the exosphere, where their vitality is lost. The subsequent excitation and ionization of atmospheric elements transmits light of differing shading and unpredictability.

The type of the aurora, happening inside bands around both polar areas, is additionally subject to the measure of increasing speed conferred to the accelerating particles. Hastening protons for the most part deliver optical emanations as incident hydrogen particles subsequent to picking up electrons from the air. Proton auroras are normally seen at lower latitudes. Auroras are once in a while observed in latitudes just below auroral zone, the minute a geomagnetic storm incidentally grows the auroral oval. Vast geomagnetic tempests are most regular amid the top of the sunspot cycle of eleven-year. An aurora may seem overhead as a “crown” of beams, transmitting from an inaccessible and evident focal area, which comes about because of the point of view.

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