Aurora is a natural light display, seen in and around the sky of Arctic & Antarctic regions. Aurora is commonly known as polar lights or northern & southern lights, which can only be seen in the clear, uncloudy, dark sky.
Visibility of northern lights during daytime or cloud coverage is really difficult. Aurora’s average activity is visible at high latitudes of both North & South Poles, in places like Alaska Fairbanks, Dawson, Yukon, Gillam, Manitoba, southern Greenland, Iceland, Norway, Northern coast of Siberia, all having great chances to view the northern lights.
Types of Aurora:
The polar lights, Aurora has four commonly known types that have varying degrees of visibility from the ground. They are in form of Patches or surface like clouds; Curves across the sky; light or dark Rays/Stripes; Coronas covering the sky, diverging between two points. The polar lights could be mild near the horizon and hardly visible but can be eminently distinguished from the clouds, due to the fact that stars are seen clearly during the occurrence of miraculous lights.
Reasons for Northern Lights Display:
In 1960, the immediate reason for the excitation of the atmospheric constituents was discovered from the information conveyed by a Canadian rocket, which noticed electronic flux entering the Earth’s upper atmosphere. Since then, extensive research work has been made by using rockets & satellites. Consequent findings explain that the electrons coming down in the sky, become extremely accelerated in an area of 10K-km before plunging into the Earth’s atmosphere and form aurora arcs/other bright forms. Most often, sky-watchers observe a gigantic display of polar lights, created by the peak of electronic energy distribution, aligned with local directions of the earth’s magnetic field.
The sun is 93+ million miles away from earth, but its effects extend far beyond its surface. The strong solar wind or great sun storms throw clusters of solar particles into the universe. This causes magnetospheres’ disturbances, to the extent of altering the charged particles trajectory in the solar wind as well as plasma of magnetosphere. The charged particles emanating from the sun strike atoms in Earth’s atmosphere, and create a higher energy state of the electrons.
The accelerated electrons move down to the Polar Regions, due to the strong magnetic fields of the earth, where they collide with oxygen & nitrogen atoms and molecules within Earth’s atmosphere. This collision results in higher excitement of atoms and molecules, with the help of electronic energy transformation.
The energy so formed releases in the shape of photon i.e., light similar to neon lights, after relaxing back by these atoms and molecules. The precipitation of electrons and protons in the upper atmosphere, ionizes its constituents, resulting in the emission of “varying & complexed lights”, called Aurora.
During an aurora activity, a neon light function carries out in which electricity is used to excite the atoms present in neon gas within a glass tube. The aurora works in a similar fashion, but on a far vast scale. The density of accelerated particles produces a band form of aurora around both the Polar Regions. It is important to know that different gases in the earth’s atmosphere give off different colors while excited, but most of the time, aurora has green colors. The proton aurora can be observed even at the lower altitudes. The northern lights are formed by the collision of electrons with the upper layer of the earth’s atmosphere.
Interesting Facts about Aurora:
Some interesting, natural facts about the aurora activities are mentioned here:
⮚ We can watch splendid, dancing aurora lights of various types around magnetic poles of the northern & southern hemispheres. The electrically charged particles streaming out from solar wind, collide with gaseous atoms & molecules while entering Earth’s atmosphere and create aurora.
⮚ The electrons and protons first gain energy from a collision, get back to normal, and release this energy in the shape of lights (aurora). This is just like the neon light phenomenon.
⮚ The electrons from the sun, always travel along magnetic field lines in Earth’s magnetosphere, which is a comet-shaped bubble around Earth.
⮚ Earth’s upper atmosphere is very thin and cannot carry sound, so aurora has no sound because of the distance. However, people claim to hear some sort of whistling, hissing, or bristling sounds during aurora display in the sky. Only once, an audible sound was detected by a microphone associated with the aurora.
⮚ The corona, the outermost layer of the Sun’s atmosphere has a 1M+ degree temperature, which causes hydrogen atoms to split into electrons & protons. These particles called plasma, being exceedingly hot, break the gravitational force of the sun and blow away in all directions.
⮚ When the solar wind is strong, more active and brighter aurora is observed on Earth.
⮚ Most of the time, Aurora has green colors, but we can also watch red, violet, and white colors. Oxygen causes green color, and nitrogen gives off blue or red color aurora.
⮚ It is a natural phenomenon that aurora always exists at some of the other places, but it exists at very high latitude or faint enough to see.
⮚ We must have a dark and clear sky to watch aurora.
⮚ Alaska, Canada, and Scandinavia are the best places to view the aurora, during winter. The aurora activity is stronger at the equinox, rather than at the solstice. It proves from the fact that aurora seen over interior Alaska, is twice as high at equinox as it is at solstice. So, late February to early April is the best aurora viewing month in Alaska.
Rare visibility in the USA:
The skies of the Northern US, parts of Minnesota & Alaska had a rare display of northern lights on the morning of 12th May 2021. Parts of Canada, Europe & UK, and New Zealand in the southern counterparts also observed glimpses of polar lights, on the same day. A surprising storm rocked the Earth’s magnetic field on Wednesday and displayed northern lights, watched by hued sky-watchers in these parts of the world. There is every possibility for repetition of such display, due to the energetic atomic & molecular particles present in the upper atmosphere. Aurora may only be rarely seen during large auroral events in the US & Europe. Way back in 1958, the aurora became visible from Mexico City.
Aurora visibility is great in the northern latitudes, during winter in Canada, Alaska & Scandinavian skies. The period between the end of February to early April is considered the best to view aurora in Alaska, due to stronger auroral activity at the equinox (equal length of day & night when the Equator passes the center of the sun on 22nd September & 20th March, each year) than at solstice (shortest and longest days of the year i.e., 21st June & 21st December, when the sun reaches its highest or lowest points).
**Watch videos of amazing, dancing Northern Lights: