Over the weekend, Earth experienced a surge in auroral activity following a huge solar flare that released energetic particles into space. This event resulted in vivid aurora displays being visible in both the northern and southern hemispheres, with sightings as far south as Hawaii and as far north as Mackay. While this surge in activity may have subsided, the Sun is on track to reach the peak of its 11-year sunspot cycle, promising more intense aurora displays in the upcoming year.

The mesmerizing glow of the aurora is a result of charged subatomic particles, primarily electrons, colliding with Earth’s atmosphere. These particles are continuously emitted by the Sun, particularly during periods of heightened solar activity. Earth’s magnetic field typically shields the majority of our atmosphere from these charged particles, but near the poles, they can infiltrate and create havoc.

Our atmosphere consists of approximately 20% oxygen, 80% nitrogen, and trace amounts of other gases. When high-speed electrons collide with oxygen molecules in the upper atmosphere, they split the molecules into individual oxygen atoms. These oxygen atoms become excited due to the collision, causing their electrons to arrange in an unstable manner that can be stabilized by emitting light.

The diverse colors seen in an aurora are a result of various elements emitting light when energized. For instance, copper atoms produce a blue light, barium emits a green light, and sodium atoms create a yellow-orange hue. These emissions follow the principles of quantum mechanics, leading to rapid transitions in excited states.

The dominant green light in the aurora originates from oxygen atoms transitioning from the “¹S” state to the “¹D” state. This transition occurs relatively slowly, taking almost a second on average before emitting the green photon. The “forbidden” transition from the “¹D” state to the “³P” state results in the emission of red light, appearing predominantly at higher altitudes due to its slow occurrence and limited collisions with other molecules.

In addition to green and red, ionized nitrogen molecules can emit blue and red light, contributing to a magenta hue at lower altitudes. While these colors are visible to the naked eye during bright aurora displays, they appear more intense when captured by cameras due to longer exposure times and superior color sensing capabilities.

Despite the vibrant colors captured on camera, the naked eye can perceive the stunning array of hues during intense aurora events. Cameras benefit from extended exposure times, enabling them to capture dimly lit scenes that our eyes may struggle to discern. Moreover, the color sensors in our eyes are less effective in low-light conditions, often resulting in a black-and-white perception.

When the aurora reaches a sufficient intensity, the colors become distinctly visible even to the naked eye, offering viewers a firsthand experience of nature’s captivating light show.

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