Aurora refers to several different phenomena that occur in the Earth’s atmosphere and are characterized by the appearance of colourful lights in the sky. The most well-known type of aurora is the aurora borealis, also known as the northern lights, which are visible in the northern hemisphere. The counterpart in the southern hemisphere is called the aurora australis or the southern lights.
Auroras are caused by the interaction of the Earth’s magnetic field with charged particles from the Sun. The Sun constantly emits a stream of charged particles called the solar wind. When these particles reach the Earth, they are deflected by the planet’s magnetic field and become trapped in the magnetosphere, a region around the Earth where the magnetic field dominates.
As the charged particles become trapped in the magnetosphere, they collide with atoms and molecules in the upper atmosphere, primarily oxygen and nitrogen. These collisions excite the atoms and molecules, causing them to release energy in the form of light. The different colours observed in an aurora are determined by the type of gas and the altitude at which the collisions occur.
The most common colours of an aurora are green, red, and yellow, which are produced by excited oxygen molecules at different altitudes. Oxygen atoms at lower altitudes emit a greenish-yellow light, while oxygen atoms at higher altitudes emit a red light. Occasionally, blue and purple hues can also be observed, which result from nitrogen molecules.
Auroras are most commonly seen in polar regions, closer to the Earth’s magnetic poles, due to the shape of the magnetic field lines. However, during periods of high solar activity, such as solar flares or coronal mass ejections, auroras can be visible at lower latitudes as well.
The phenomenon of aurora has fascinated people throughout history, leading to numerous cultural and mythological interpretations. Today, they continue to be a popular tourist attraction, with many people traveling to regions like Alaska, Canada, Scandinavia, and Antarctica to witness the breathtaking display of lights in the night sky.