Why do the Northern Lights have different colors?

Lately, The Earth was hit by the largest solar storm recorded since 2003. As in such explosions, a wave of particles energized by the Sun was sent into space. Once they reached our planet, people around the world began to observe aurorae in vivid colors, even in places where this phenomenon is not so common.

Although normally confined to polar skies, northern lights and astral lights caused by the recent solar storm have been detected at unusual latitudes, both as far south as Hawaii and as far north as Mackay on Australia’s east coast.

Anyone who misses this light show for whatever reason can rest assured that the Sun is near the peak of Solar Cycle 25, when sunspots occur on average every 11 years. More aurora are expected next year.

How do atoms produce northern lights and astral lights?

Subatomic particles (mostly electrons) carried by the Sun reach Earth every day, but they gradually lose their energy as they interact with atoms and molecules in our atmosphere.

According to quantum mechanics, electrons do not revolve around the atomic nucleus in fixed orbits, as we learn at a fundamental level. Instead they occupy orbitals and In the case of solar particles, they are in an excited state and drift towards a higher, more unstable energy level.

When they collide with the atmosphere they “relax”, i.e. It releases excess energy in the form of light.

Why are aurora lights colorful?

Timothy Schmidt, a chemistry professor at the University of New South Wales in Australia, said in an article published on The Conversation platform: draws an analogy between auroras and fireworks When they explode, they produce light of different colors depending on the atoms of the different elements from which they are produced.

“Copper atoms give off blue light, barium is green, and sodium atoms give off a yellow-orange color “You may have seen this in old street lamps,” explains Schmidt. Schmidt says these emissions are “allowed” by quantum mechanics, causing excited oxygen atoms to emit light very quickly.

Aurora borealis in green color

The green light most commonly seen in auroras is produced by oxygen atoms. when they relax from a higher energy state (¹S) to a lower energy state (¹D). Although we see this as instantaneous, Schmidt says this process is relatively slow, taking almost a second on average to occur.

Northern lights are red

In some cases, even after emitting a green photon, the oxygen atom remains in an excited state and quantum relaxation is “not allowed”. It then performs another “forbidden” transition, meaning in the ¹D state it takes even longer (about two minutes), until it finally relaxes and emits red light.

other colors

Although the most common colors in auroras are green and red, other colors also occur in less intensity. This is the case, for example, for ionized nitrogen molecules (N2?), which have a positive charge because they are missing an electron. In this case, blue and red lights are produced, resulting in magenta color at low altitudes.

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