The Aurora Borealis, often known as the northern lights, are stunning dancing waves of light that have mesmerized humanity for millennia. Despite its beauty, this amazing light show is also rather a violent spectacle.
The magnetic field of our planet shields us from the assault of energetic solar particles, which may travel up to 45 million miles per hour (72 million kilometers per hour) in our upper atmosphere.
As Earth's magnetic field leads the particles toward the poles, the dramatic process develops into a cinematic atmospheric phenomenon that astonishes and excites both scientists and skywatchers.
What does History say about it?
The term "aurora borealis" was first used in 1619 by Italian astronomer Galileo Galilei, who named it after the Roman goddess of dawn, Aurora, and the Greek god of the north wind, Boreas. However, the earliest known instance of the northern lights is thought to be a 30,000-year-old cave painting in France.
Since then, cultures all across the world have marveled at the celestial phenomena and given the dancing lights a variety of origin stories. The northern lights are said to be ghosts having a game of ball with a walrus head in a North American Inuit legend, while the Vikings believed the phenomena was light reflecting off the armor of the Valkyrie, the magical maidens who carried heroes into the afterlife.
It wasn't until the start of the 20th century that the science underlying the northern lights was postulated. According to the theory put out by Norwegian physicist Kristian Birkeland, electrons that were released from sunspots and were directed toward the poles by the Earth's magnetic field formed the atmospheric lights.
What are the Northern and Southern lights?
The solar wind is the result of the sun's constant ejection of charged particles from its corona, or upper atmosphere. The aurora is created when that wind collides with Earth's ionosphere or high atmosphere. The phenomenon is known as the northern lights (Aurora borealis) in the Northern Hemisphere and the southern lights in the Southern Hemisphere (Aurora australis).
The solar wind is always there, although the sun goes through an approximately 11-year cycle of activity with its emissions. There are periods of calm between massive storms that blast Earth with enormous quantities of energy. The northern lights are most frequent and brightest around this time. According to the U.S. National Oceanic and Atmospheric Administration, the most recent solar maximum, or time of peak activity, occurred in 2014. This puts the next one in around 2025.
The chemical makeup of Earth's atmosphere determines the vivid hues of the northern lights.
Stages of the auroras-
1. Daytime aurora is caused when solar particles strike Earth and travel along invisible magnetic lines to the dayside of the poles. High latitude regions like Svalbard are the only ones where daytime aurora may be observed.
2. The same as a flag in strong winds, magnetic lines break on Earth's dayside and our magnetosphere spreads outward on Earth's night side. These lines are followed by solar particles like beads on a thread.
3. The magnetic lines eventually unite and merge on the night side. The same idea holds for wind around a structure; if you stand just in front of a building on the windward side, you won't feel anything, but as you move away from the building, you'll gradually start to feel the wind again as the wind's route re-connects. The solar wind particles flood back towards Earth when this reconnection takes place because they have nowhere else to go.
4. Between 75 and 800 kilometers above the surface of the Earth, the particles shower down and combine with gases in our atmosphere to produce the light display. By interacting with atmospheric gases at differing altitudes, solar wind electrons produce a variety of colors.
Auroras on other planets-
Three different forms of Martian auroras have been categorized by scientists. One is a dayside event that only happens on the planet, another is a broad nighttime characteristic fuelled by powerful solar storms, and a third is a much more patchy nightside occurrence.
Soon after touching down on Mars in early 2021, the Hope Mars orbiter—the United Arab Emirates' first ever interplanetary mission—was able to snap a picture of the midnight aurora. Scientists may be able to comprehend this puzzling behavior better thanks to the probe's observations.
The magnetic field of Jupiter is 20,000 times greater than that of Earth, thus the auroras that burn in its skies are far brighter. The majority of the particles that generate the planet's auroras are sent into space by its nearby moon Io, the solar system's most volcanically active body. This means that the Jupiter lights aren't only caused by the solar wind.
Even in distant solar systems, there appears to be an auroral activity, according to astronomers. For instance, two studies published in October 2021 announced the discovery of radio waves released by several red dwarf stars, which are smaller and fainter than the sun.
The sky of exoplanets should also have auroras very often.
Where to see it?
Any location in the "auroral zone," or the region within about 1,550 miles (2,500 kilometers) of the North Pole, is the greatest location to observe the northern lights, according to the Troms Geophysical Observatory in Norway. Although it can spread further south during extremely powerful solar storms, there is where the aurora most usually appears.
When the sky becomes sufficiently dark to observe the aurora, between September and April is the greatest time of year to see the northern lights. (Locations in the far north enjoy the midnight sun or summer days with 24 hours of daylight.) According to the Geophysical Institute of the University of Alaska Fairbanks, the biggest activity often occurs between 9 p.m. and 3 a.m. . Remember the moon's phases, as a brilliant full moon could illuminate the night sky. Because you won't be able to see the aurora through the clouds, you should also check your local weather prediction.
The Auroras should definitely be a part of your bucket list. Until next time, stay happy and stay safe.