The Northern Lights are universally recognized as one of the most important and spectacular sights of the far north. Observed by humans for generations, the Northern Lights set the sky ablaze in a panoply of brilliant colors. Traditionally the source of many myths and legends, the Northern Lights are now accessible to tourists around the world due to modern technology and travel. However, some tourists might ask the question: does the moon have any effect on the Northern Lights?
The answer is yes and no. While a full moon can drown out weaker auroras, strong auroras will still appear regardless of the moon’s brightness, and can indeed make the Northern Lights even more of a striking experience. Read on to learn how the full moon affects the Northern Lights.
The Northern Lights and the Full Moon
As a phenomenon, the Northern Lights can only be viewed at night. This is because the rays of the sun drown out the colors that create auroras in the first place. It is because of this that auroras are best viewed between the months of September and April, because this is the only time in the Arctic where there is sufficient darkness for them to form. Due to the Earth’s axial tilt, the Arctic experiences near-constant daylight during the summer and near-constant darkness in the winter, precluding the possibility of witnessing auroras during the former.
While the moon may appear bright in the night sky, the moon does not generate light of its own. “Moonlight” is in fact a reflection of light generated by the sun. This is why the moon cycle exists, with the moon going from full moons (where the entire moon is visible) to new moons (where the moon cannot be seen at all).
This cycle occurs because of the moon’s revolution around the Earth. Due to tidal locking, the same side of the moon is always visible from the Earth’s surface; the “dark side” of the moon can never be seen from the Earth. During a new moon, the moon and sun are in the same position relative to Earth, causing sunlight to fall on the far side of the moon and making the moon invisible to Earth-bound observers. During a full moon, the moon and sun are on opposite sides of Earth, making the sunlit side of the moon fully visible from Earth’s surface.
Because auroras are generated by solar wind (the scientific name for the streams of particles emitted by the sun), the moon has no effect on the occurrence of auroras themselves. When solar wind comes into contact with the Earth’s magnetosphere, it is dissipated and neutralized. Much of the magnetosphere is located in outer space, but because the magnetosphere is generated by the North and South Poles, the magnetosphere intersects with the atmosphere at those points. When solar wind enters the atmosphere, it causes a chemical reaction that is visible as the Northern Lights.
However, the large amounts of light the moon gives off can have an effect on the visibility of an aurora by drowning out the Northern Lights. The same effect is caused by light pollution from cities and other human settlements, which is why the best aurora viewing locations are in rural, isolated areas. In general, the weaker an aurora, the more likely it is to be drowned out by a full moon. Moonlight is capable of obscuring weaker stars from view, and it is also capable of dissipating aurora light from the point of view of observers on the ground.
However, stronger auroras are able to withstand the light generated by a full moon. Indeed, depending on the strength of the aurora, a full moon can actually make the Northern Lights look more spectacular. Because of this, some Arctic photographers actually prefer to photograph auroras during full moons, because the presence of the moon causes the sky to turn dark blue, instead of the normal black during a regular aurora.
The lunar cycle takes roughly one month to complete, with only one full moon during that time. Because of this, you are unlikely to witness an aurora during a full moon unless your trip is timed to occur during one, since the full moon only lasts for a single day. However, if you are lucky enough to view a strong aurora during a full moon, it can make your experience all the more memorable.
Despite what some say, the moon has no effect on auroras themselves. While the full moon is capable of drowning out weaker auroras, stronger auroras are able to withstand the sheer amounts of light given off by a full moon, and their presence can actually make auroras more beautiful. If you’re curious about the Northern Lights, with or without a full moon, book a trip and prepare for one of the most exciting trips of your life.