What causes the Northern Lights?
The aurora, a breathtaking phenomenon, graces the skies near the Earth’s poles, known as the aurora borealis in the north and the aurora australis in the south. These celestial displays have captivated humanity for centuries and continue to inspire awe, fear, and wonder. Today, photographers endeavor to capture the beauty of these events, showcasing their remarkable images at exhibitions like the Astronomy Photographer of the Year.
What Triggers the Aurora Borealis or ‘Northern Lights’?
The mesmerizing lights we witness in the night sky originate from activity on the surface of the Sun. Solar storms release vast clouds of electrically charged particles, some of which travel millions of miles and may collide with Earth. While most of these particles are deflected away, some become trapped in the Earth’s magnetic field, funneling down towards the poles. Upon entering the atmosphere, these particles collide with atoms and molecules, heating them and causing them to glow—a process akin to heating a gas. The distinctive wavy patterns and ‘curtains’ of light in the aurora are shaped by the Earth’s magnetic field lines.
Understanding the Colors of the Aurora
Different gases emit different colors when heated, a phenomenon mirrored in the aurora. Nitrogen and oxygen, the primary gases in Earth’s atmosphere, produce varying hues during these displays. Oxygen contributes to the green hue, while nitrogen can manifest as purple, blue, or pink. Occasionally, high-altitude oxygen interactions with solar particles produce a scarlet red color, particularly during energetic auroras.
Can You Witness the Aurora Borealis in the UK?
Although the aurora borealis is typically visible in polar regions, it can occasionally be seen in the UK, particularly in the north. Regions further north, such as Cornwall and Kent, have also witnessed this awe-inspiring spectacle. Tools like Lancaster University’s AuroraWatch UK website provide estimates of aurora visibility based on geomagnetic activity, offering enthusiasts a chance to witness this natural wonder.
Exploring Auroras Beyond Earth
Auroras are not exclusive to Earth; planets with atmospheres and magnetic fields also boast these captivating displays. Scientists have observed auroras on Jupiter, Saturn, Uranus, and Neptune, each with its unique characteristics. Even Mars, lacking a global magnetic field, exhibits auroras, albeit in a more widespread manner.
Solar Flares and Geomagnetic Storms: Catalysts of Auroral Displays
Solar flares, immense explosions on the Sun’s surface, expel streams of charged particles into space, eventually reaching Earth and sparking auroral activity. Geomagnetic storms, triggered by colossal solar explosions called coronal mass ejections, unleash clouds of hot plasma that interact with Earth’s magnetic field, intensifying auroral phenomena.
The Dynamic Solar Cycle and Auroral Occurrence
Solar activity ebbs and flows in an approximately 11-year cycle, with peaks in solar flares and auroral displays. Although solar activity has recently declined, auroras can still manifest at any time, reminding us of the Sun’s profound influence on our planet and the universe beyond.
