The recent surge in solar activity, including powerful solar flares and coronal mass ejections (CMEs), has increased the chances of witnessing spectacular auroras, known as the northern lights (aurora borealis) and southern lights (aurora australis), in both hemispheres. What is amazing, is the colours are creating some visibly stunning variations and visible over wider areas during May 2024. This is likely due to the ongoing intense solar storms elevated geomagnetic activity associated with the approaching solar maximum.
While solar flares themselves do not directly impact Earth’s energy infrastructure, their associated effects, such as geomagnetic storms and ionospheric disturbances, can have significant consequences for power grids, communication systems, and various energy-related technologies. Monitoring and preparing for space weather events is crucial for mitigating potential disruptions to Earth’s energy systems.
What Causes the Aurora?
Auroras are created when charged particles from the Sun, carried by solar wind and CMEs (Coronal mass ejection is a massive burst of solar wind and magnetic fields rising up from the solar corona into space), interact with Earth’s magnetic field. These particles are funnelled towards the polar regions, where they collide with gases in the upper atmosphere, causing them to emit colourful lights. The colours depend on the types of gases and their altitudes, with oxygen producing green and red hues, and nitrogen creating blues and purples. Clear dark skies, away from light pollution, are crucial for optimal aurora viewing.
The Current Solar Maximum
The Sun follows an approximately 11-year cycle of activity, with the current cycle (Solar Cycle 25) expected to reach its peak, known as solar maximum, in mid to late 2024. This period is characterised by an increased number of sunspots and more frequent and intense solar flares and CMEs. The most recent solar flare was recorded as an X4.5 class flare. While very powerful, it was not the strongest ever recorded. The largest solar flare ever recorded was an X28+ class flare that occurred on November 4, 2003, during the famous Halloween solar storms of 2003 hurling a CME’s towards Earth.
Nature’s Masterpiece
As the Sun continuously expels a stream of charged particles called the solar wind, along with occasional bursts of high-energy particles during solar flares and coronal mass ejections, the release photons of light in colourful displays known as the aurora borealis. When these charged particles reach Earth, some are funnelled towards the polar regions by our planet’s magnetic field lines. As they enter the upper atmosphere around 100-300 km in altitude near the poles, these particles collide with oxygen and nitrogen atoms and molecules, transferring their energy. This energy transfer excites the atmospheric gases, causing them to release photons of light in colourful displays known as the aurora borealis. Oxygen produces green and red auroral hues, while nitrogen emits blues and purples, with the colours varying based on altitude. The auroral lights often manifest as arcs, curtains, rays, or coronas, following the shape of Earth’s magnetic field lines concentrated over the polar regions. In essence, the breathtaking aurora borealis results from the interaction between charged solar particles and gases in our upper atmosphere, guided by our planet’s magnetic field near the poles.
Witnessing Nature’s Grandest Light Show
Auroras, also known as the northern lights (aurora borealis) and southern lights (aurora australis), can be seen in high-latitude regions near the polar circles of both hemispheres. The colours observed in these celestial displays depend on the gases present in the Earth’s atmosphere and the altitudes at which the charged particles from the Sun interact with them. But what do we know about the colours?
Green Auroras
Green is the most commonly observed colour in auroral displays. It is produced when energetic particles from the Sun collide with oxygen molecules at altitudes between 100 to 300 km (60 to 185 miles) above the Earth’s surface. The green hue is the result of the excited oxygen molecules emitting photons of green light as they return to their normal state.
Red Auroras
Red auroras are less frequent and typically associated with intense solar activity. They occur when the charged particles interact with oxygen atoms at higher altitudes, generally between 300 to 400 km (185 to 250 miles). At these altitudes, the lower density of oxygen atoms causes them to emit red light when excited by the solar particles.
Blue and Purple Auroras
Blue and purple auroras are relatively rare and tend to appear during periods of high solar activity. These colours are produced when the solar particles collide with nitrogen molecules at lower altitudes, usually below 100 km (60 miles). The blue and purple hues result from the excited nitrogen molecules emitting photons in those wavelengths.
Pink and Yellow Auroras
Pink and yellow auroras are even rarer and are typically a combination of other auroral colours. Pink often appears as a mixture of red and green or blue auroras, while yellow is a blend of red and green.
While auroras provide a breathtaking celestial display, increased solar activity can also disrupt communication systems, GPS, and power grids on Earth. However, space weather forecasters at organisations like NOAA’s Space Weather Prediction Center closely monitor solar activity to provide timely alerts and warnings.
In the coming years, leading up to and around the solar maximum later in 2024, we can expect more frequent and intense auroras visible across wider regions of the globe. This presents an exciting opportunity for aurora chasers and stargazers to witness the mesmerising dance of lights in the night sky, while also highlighting the importance of understanding and preparing for the potential impacts of space weather on our technology and infrastructure.
