What are the Northern Lights or Aurora Borealis?
All of us have seen the magnificent pictures of the iridescent skies and the elusive phenomenon that is Aurora Borealis – better known to us as Northern Lights. This incredible light show is still a subject of research in recent times and scientists take great interest in them. So what are the Northern Lights?
Formally referred to as the aurora borealis, the northern lights represent a scientific phenomenon, occurring in the atmosphere, where oscillating waves of green, purple, and red lights gracefully move across the skies. This event materializes when streams of energized solar particles known as solar wind relentlessly collide with our planet’s atmosphere.
Benefiting from the shielding effect of Earth’s magnetic field, we remain safeguarded from these impacts on the terrestrial surface. These particles journey along the magnetic lines of force toward the poles of the globe, instigating an energetic interchange that gives rise to the vivid luminescence seen in the sky.
While the northern lights manifest in the northern hemisphere, an analogous phenomenon in the southern hemisphere is formally termed the aurora australis, though colloquially referred to as the southern lights. It is interesting to note that, the northern and southern lights, or aurora australis, occur simultaneously but the inverse seasons imply they generally aren’t visible at the same time.
Read more: The Science behind Auroras
What causes the Northern Lights?
An article published in the journal Nature Communications in 2021, by Schroeder et. al. described the science behind the occurrence of the natural light show – aurora borealis.
This paper described that the phenomenon of the northern lights takes place as a result of disruptions in the sun influencing Earth’s magnetic field. This interaction gives rise to cosmic undulations referred to as Alfvén waves, which propel electrons at elevated velocities into Earth’s upper atmosphere, where they instigate the creation of the aurora.
The scientists further go on to elaborate on how this interaction between the sun and the Earth’s magnetic field works. The sun’s volatile nature can lead to violent events like geomagnetic storms that have far-reaching effects.
These disturbances can tug on Earth’s magnetic field, causing it to stretch and then snap back, generating powerful Alfvén waves roughly 80,000 miles above the surface. These waves accelerate as they approach Earth due to its magnetic influence, and electrons occasionally catch a ride on these waves, achieving speeds of up to 45 million miles per hour as they descend.
Schroeder explains this with the analogy of surfing, “In order to surf, you need to paddle up to the right speed for an ocean wave to pick you up and accelerate you, and we found that electrons were surfing. If they were moving with the right speed relative to the wave, they would get picked up and accelerated.”
Upon reaching the Earth’s thin upper atmosphere, the electrons engage in collisions with molecules of nitrogen and oxygen, inducing these molecules to become energetically aroused. As time progresses, these stimulated electrons gradually settle and emit light, constituting the visual spectacle known as the aurora.
When heated, various gasses emit distinct colors, a phenomenon observed in the aurora as well. Oxygen and nitrogen are the dominant gasses in Earth’s atmosphere, generating green hues from oxygen and shades like purple, blue, or pink from nitrogen in auroras. Additionally, scarlet red tones occur at times due to high-altitude oxygen reacting with solar particles, a phenomenon seen during particularly energetic aurora displays.
When is the best time of year to see the northern lights?
The northern lights, or the aurora borealis, have the potential to be best observed in the night sky from late August to mid-April, especially when the sky is clear and devoid of clouds. The northern lights forecast is based on the logic that although they manifest throughout the year, their luminosity is lesser than that of sunlight, resulting in their invisibility from May to July and a significant portion of August.
In actuality, the northern lights don’t occur more often during any particular season. The frequency and intensity of these lights is driven by the behavior of the Sun.
Observational space physicist Jodie Ream from MIT explains that the seasonal changes observed on Earth are a result of the regions where darkness is sufficient for these phenomena to be visible.
The polar areas, where particles are concentrated, experience extended periods of darkness during winter, creating optimal conditions for viewing the aurora. Enhanced solar activity causes the lights to travel deeper into the atmosphere from the north pole, potentially allowing residents in Arctic regions and nearby areas to witness them.
Scientists note that heightened solar activity leads to more intense northern lights, potentially appearing at lower latitudes as well.
The northern lights forecast also explains that during the summer, high-latitude places have prolonged daylight hours known as the midnight sun, leaving fall, winter, or spring as the suitable seasons to witness the northern lights. The optimal times to catch this natural spectacle are during the fall and spring equinoxes, around September and March, when solar activity is at its peak.
However, the northern lights can still be observed anytime between these months throughout the winter. When it comes to the time of the day, consider these points:
- The most intense auroras are typically observed from 9 pm to 2 am, with prime viewing times falling between 11 pm and midnight.
- The period between 4 am and 5 pm usually offers too much daylight for aurora sightings, except during the darkest months and in high latitudes like Svalbard, where continuous darkness occurs from mid-November to the end of January.
Where can you observe the Aurora Borealis?
To have a successful northern light forecast in terms of places to best observe them, let us understand what the auroral zone is. The geographic area beneath the auroral oval, is the region of the northern hemisphere within an approximately 1,500-mile radius of the magnetic north pole. That encompasses most destinations within the Arctic Circle (anything north of the latitude 66°33’N – or broadly between 60 and 75 degrees), and includes Iceland, northern parts of Sweden, Finland, Norway, Russia, Canada and Alaska as well as southern Greenland.
Based on the above stated logic, multiple sources publish their northern lights forecast for the best places to observe the aurora borealis from, every year.