This winter is one of the best times to see polar lights. The next best time is in about 10 years, so you better catch them now. To stand a good chance of a polar light sighting, you need to be in the right place at the right time. An understanding of how Aurorae work and forecasts can help. This article provides the resources for both.
What Is An Aurora?
An Aurora, also known as polar lights, is a natural phenomenon caused by electrically charged particles from the sun that enter Earth’s atmosphere. Aurorae are best visible close to the planet’s magnetic poles; on Earth, as well as other planets, should you ever visit one. The Aurora Borealis or northern lights can be seen close to the North Pole, while its southern counterpart is known as Aurora Australis or southern lights.
What Causes Aurorae?
Aurorae originate at the sun, which continuously ejects matter and electromagnetic radiation into space. When the charged particles reach Earth’s magnetosphere, it re-directs some of them to its polar regions.
The particles flowing towards the poles are energentically boosted in Earth’s upper atmosphere. When they finally collide with oxygen and nitrogen atoms in the atmosphere, they can produce a spectacle of light in the sky, known as Aurora.
The following video beautifully explains how an Aurora is formed, and it concludes with breathtaking images.
When & Where Can I Best See Aurorae?
This depends on several factors.
While the sun continuously releases soloar particles, some ejections are stronger than others. Naturally, the particles take some time to reach the Earth. An ejection strong enough to cause Aurorae will be visible on Earth two to three days later.
Since Aurorae depend on the release of solar particles, they tend to be most frequent and strongest during high solar sunspot activity, which follows an 11 year cycle. We are currently in cycle 24, which reached its maximum in summer 2013. Aurorae are strongest for around 3 years around the solar cycle’s peak.
Apart from solar particle eruptions and the solar cycle, the visibility of Aurorae depends on your geographical location, as well as the local weather and light pollution.
To summarize, the best conditions for Aurora viewings are:
- high solar activity,
- during night time,
- high latitude,
- clear sky,
- little surrounding light from a city or the moon.
How Can I Predict My Chances Of Seeing An Aurora?
The level of geomagnetic activity can give a clue as to how good your chances are, depending on your magnetic latitude. The geomagnetic activity for a 3-hour period is given using the Kp index, which ranges from 0 (no activity) to 9 (maximum activity). The number reveals at which magnetic latitude you have a chance of seeing an Aurora.
For example with a Kp of 6, polar lights are potentially visible at latitudes of up to 54.2, which includes Minneapolis (55.1) or Stockholm (56) in the northern hemisphere.
For more details on how this works and to find the magnetic latitude of your city, please visit the NOAA / Space Weather Prediction Center. They also have clickable maps; in case your city is not listed, you can simply click your location to get your magnetic latitude.
Where Can I Find Out About The Current Geomagnetic Activity?
Several websites and mobile apps can inform you about and alert you to good viewing conditions in your area.
This website translates the current data into a chance of seeing Auroral activity at high, middle, and low latitude. The site also features maps for different parts of the world.
This page also offers a nice summary of spacecraft and NOAA solar data.
Aurora Notifier (Android)
This app shows the current Kp-index and you can enable notifications to alert you when a specific Kp-index is reached. Get the Aurora Notifier+ add-on to limit notifications to when it’s dark.
Aurora Forecast (Android)
Aurora Forecast provides a summary of the space weather data from NOAA, you can view recent plots, and see a forecast for the next couple of days. Alerts are a $1.99 premium feature.
When Will You See Your Next Aurora?
As you see, catching an Aurora can be a science of its own. Have you ever been lucky enough to see one? Where was it and did you plan to see it?