Mysterious Light show – Aurora

Who does not love to watch natural glimmering light show in the sky fill with tiny stars during dark, shivering midnights? There is no doubt that, seeing aurora is a popular wish in most of “Bucket lists”.

Brief:

Aurora borealis (northern lights) or aurora australis (southern lights) or aurora Polaris (polar lights), those all names are referred to this alluring natural phenomenon. Due to two main reasons seeing aurora is ‘little bit’ a rare incident. Aurora is not visible to everywhere in the world. The auroral band spread across the high-latitude regions (i.e., Canada, Norway, Australia, Finland, Iceland, Greenland) around Arctic and Antarctic. There is no special season since the aurora is almost always happens. But you cannot see them every time. To see aurora, you need a dark, clear night without clouds and light pollution. Northern lights are visible from late August to early April anytime during dark hours. Southern lights can view during fall and winter months, which stretch from March through September.

Science behind this aurora Phenomenon

Since ancient time, people have been believing myths about the Northern Lights. They make tales without any scientific understanding. With the understanding of the solar system and its activities, these stories sorted into fairy tales. If briefly explain, the light show we see is caused by electrically charged particles from space entering the Earth’s upper atmosphere at a very high speed. These electrically charged particles constantly pushing out from the sun (called solar wind), and they travel at between 300 and 500 km per second in all directions. As we revolve around the sun, a small fraction of those charged particles from the solar wind are catch by the earth. Around 98% of these particles are deflected by the Earth’s magnetic field. From those particles another small amount leak through the space of Earth’s magnetic field and are funnelled downwards towards the North and South poles. When those charged particles hit the Earth’s atmosphere, electrons move to higher-energy orbits, further away from the nucleus. Then electrons move back to a lower-energy orbit, it releases a particle of light or photon. This creates glowing rings around the north and south poles caked as auroral ovals.

Auroral Colors

The colors in the aurora differ from each other according to give off gas in earth’s atmosphere.

Green Aurora: The most common auroral colour. When the solar wind hits millions of oxygen atoms in the Earth’s atmosphere at the same time, it excites their electrons for a time and then they decay back to their original state, they emit the green hue.
Red Aurora: The red light we sometimes see is also reasoned by oxygen atoms. These particles are higher up in the atmosphere and are subject to a lower energy red light emission. The red colour is always there, but our eyes are five times less sensitive to red light than green, so we can’t always see it.
Purple Aurora: Nitrogen is a main gas element in Earth’s atmosphere. When the charged particles from the solar wind hit nitrogen atoms to excite them. Once the nitrogen atoms begin to decay, they emit a purple hue.
Red and purple are rare to see, and usually only happens during a particularly active display.

Multicolored light show – Tromsø, Norway – Photo by Lightscape