At any given moment, the Sun ejects charged particles from its corona, or upper atmosphere, creating the solar wind. When this wind collides with the Earth's ionosphere or upper atmosphere, the aurora is born.
In the Northern Hemisphere, the phenomenon is called northern lights (aurora borealis), and in the Southern Hemisphere - southern lights (aurora australis). Today, the earth was hit by a strong solar storm that could cause the northern lights to appear further south in the sky than usual.
"These particles are drifted toward Earth's poles by our planet's magnetic field and interact with our atmosphere, depositing energy and causing fluorescence," Billy Teets, director of Vanderbilt University's Dyer Observatory in Nashville, Tennessee, told Space.
The bright colours of the northern lights are dictated by the chemical composition of the Earth's atmosphere.
"Each type of atom or molecule, whether it's atomic hydrogen or a molecule like carbon dioxide, absorbs and emits its own unique set of colours, which is analogous to how each person has a unique set of fingerprints," Teets explained.
"Some of the dominant colours seen in auroras are red, a hue that comes from nitrogen molecules, and green, which comes from oxygen molecules," he continued.
What causes the movement and shape of the aurora borealis?
The ever-changing data from the Sun, the different reactions of the Earth's upper atmosphere, and the motion of the planet and particles in near-Earth space all work together to cause different movements and shapes of auroras. From them, we can learn about the physics that happens further out in space along the Earth's magnetic field lines.
What do the auroras tell us about the Earth's atmosphere?
The auroras tell us a lot about the Earth's upper atmosphere, including its density, composition, flow velocity, and the strength of the electric currents flowing in the upper atmosphere. They, in turn, tell us about the Earth's magnetic field, how it extends in space and how it changes dynamically. All of this is important for protecting Earth and space technology from the dangers of "space weather," of which the aurora is a part.
Are there auroras on other planets?
Yes! Auroras are also seen from planets with magnetic fields and atmospheres that differ greatly from Earth's.
While the solar wind is constant, the solar emission goes through an approximately 11-year cycle of activity. Sometimes there is a lull, but other times there are huge storms that bombard the Earth with enormous amounts of energy. This is when the northern lights are brightest and most common.
Lucky for aurora hunters, we're currently approaching the solar maximum, which is expected to peak between early 2024 and late 2025. Scientists can't pinpoint exactly when the solar maximum will occur, but we do know that it is on its way.
The best place to view the Northern Lights is any destination in the "Aurora Zone" — the area within a 2,500 km radius of the North Pole, according to the Geophysical Observatory in Tromsø, Norway. This is where the aurora most often occurs, although during particularly strong solar storms the phenomenon can extend further south. | BGNES
