The world seems to have been transfixed these last two days by the magical displays of lights in the sky across the world. The aurora borealis and aurora australis, meaning “northern lights” and “southern lights” respectively, are two natural phenomena that are fairly rare, occurring only in a small slice of the sky near the poles. However, due to the ongoing solar storm that has been categorised as “extreme”, the auroras have been visible to observers in the UK, Europe, some US states, all the way to Tasmania in Australia.
On social media, photos of the auroras have created a buzz, as more people than ever before are able to enjoy this once-in-a-lifetime experience. In fact, solar storms appear periodically, roughly peaking around every 11 years. On top of that, this is the first extreme solar storm since 2003, making the auroras this year the first of their kind in the internet age.
So, what are these solar storms that cause the auroras? What is the science behind how they are formed?
A solar storm is an event where enormous clouds of electrically charged particles are spewed out into space from the sun’s surface. These are powerful ejections, and the particles can travel millions of miles in every direction, including towards our Earth.
When these particles do reach Earth, some of them are captured by the planet’s magnetic field, the poles of which are to the extreme north and south. While most of the solar particles are deflected away by the power of the magnetosphere, the captured particles heat up–or excite–the atmospheric particles in our skies and that is what makes them light up in different colours.
This also explains the beautiful patterns and curtain-sheet like effect that is observed in auroras. The Earth’s magnetic field can be imagined as a collection of countless lines drawn between the two poles, shooting straight up from one pole at first and then bowing around to shoot straight back into the other pole. The auroras follow these lines, as particles at specific altitudes light up in one colour to create mesmerising curtains of space lights.
The different colours in auroras are caused by the different gases that are prevalent in our atmosphere. The most common gas is nitrogen, which makes up over three quarters of air, and the excitation of nitrogen leads to blue, pink and purple auroras. Oxygen, on the other hand, is responsible for the green colour, possibly the most iconic colour for auroras.
The usual intensity with which solar flares take place only lead to displays of aurora in the poles, but the current extreme geomagnetic storm means a rare celestial event is taking place right now, and the aurora is visible in way more areas of the world than usual. Of course, an extreme geomagnetic storm has some risks too. The last time it happened in 2003, power outages were observed in countries in Northern Europe. This time around, international space observatories are on high alert to make sure that expensive and vital infrastructure like power stations, space stations, and satellites remain protected from an angry sun’s hot wrath.
