Tracking Northern Lights: How to Read Aurora Borealis Forecast

Learn to read an Aurora Borealis forecast. We explain the best websites for tracking Northern Lights and demystify the scientific language, to help you work out when & where to see the lights.

To read an aurora forecast and track northern lights, it is essential to understand what causes the aurora and how they are formed. This way you will understand why certain parameters are used in tracking northern lights and forecasting tools, and what difference their values make in your ability to see the northern lights.

In this article we will give you a quick overview of the science. We then explain in detail how to read an aurora forecast, plus recommended websites for northern lights tracking and forecasts.

By the end of this article you’ll have a good idea of how to read an aurora borealis forecast, and know how to use northern lights tracker websites to predict aurora visibility. And most importantly, you can wow your friends with your newfound geek status as an aurora tracker. Let’s dive in.

Article Contents:

• What Causes the Aurora? The Science
• How to Read Northern Lights Tracking & Forecast Tools
• Websites for Forecasting & Tracking Northern Lights

What Causes the Aurora? The Science

Auroras occur in the upper levels of the atmosphere, and are caused by the interaction of cosmic radiation with the planet’s poles.

We get this radiation as a result of solar flares (coronal mass ejections). These are in effect explosions on the surface of the sun, which release billions of tons of hot plasma into space. This radioactive material travels from the sun to the Earth at a rate of more than 2 million mph. As these particles interact with the magnetic field of our planet, they create ionization in the atmosphere. This interaction causes glowing atmospheric lights to appear in the sky around the poles, which we call the aurora borealis (northern lights) and aurora australis (southern lights).

After a solar flare has been seen on the surface of the sun, it takes a total of two days for those particles to travel the distance from the sun to the planet. However, there have been several noted occasions in which these particles arrive in as little as 18 hours. The speed at which the charged particles reach the planet, and interact with the earth’s magnetosphere, determines the overall strength of the aurora borealis and aurora australis.

We cover this topic in greater detail in our article on the science of the aurora, so head over there if you want to learn more about the science. Next, we explain what the auroral oval is and why latitude matters for aurora visibility, and how geomagnetic storms affect aurora visibility.

Understanding the Auroral Oval and Latitude

The main thing that you need to know is that the auroral oval (aka auroral zone) is the location in which the vast majority of the northern lights (and southern lights) will appear around the globe.

The auroral oval itself is only about 3 to 6 degrees wide, occurring at latitudes near 70 degrees (north and south). The further away from the magnetic poles, you are, the harder it will be to view the aurora. Due to Earth’s tilt, and the way in which the solar winds blow around the planet, the auroral zone is stretched out along the leeward side of the winds forming an oval rather than a ring.

Polar Cap Zone vs Auroral Zone vs Sub-Auroral Zone

When it comes to the aurora borealis and the aurora australis, the atmosphere is broken down into 3 distinct zones commonly referred to as the polar cap zone, the auroral zone, and the sub-auroral zone. Most of the auroral activity can be viewed from within the auroral zone, also known as the auroral oval.

According to Space Weather Canada, the three regions are defined as follows:

• POLAR CAP ZONE (77-90° latitude): The polar cap zone extends from the magnetic pole, which is located at 90 degrees, to about 77 degrees of latitude.
• AURORAL ZONE (63-77° latitude): The auroral zone is generally situated from 77 to 63 degrees of latitude away from the magnetic poles. This is considered the prime aurora viewing area.
• SUB-AURORAL ZONE (49-63° latitude): The sub-auroral zone stretches out past 63 degrees and extends down to 49 degrees, and represents the weakest geomagnetic activity.

When we look at maps, we generally want to seek out areas in the auroral zone/oval (63-77° latitude) for viewing the lights, which we discuss further in our article on how to choose the best place to see the northern lights.

It is important to mention that with regard to latitude, there are actually two types of latitude: geographic latitude and geomagnetic latitude. Across this website we mostly use geographic latitude, because it is most straightforward for non-scientists to understand. Geomagnetic latitude moves over time, and is slightly different from geographic latitude. Geomagnetic latitude (aka magnetic latitude) is technically more correct for aurora forecasting, so you might see this term used. Unfortunately, there is no easy way to convert from geographic latitude to geomagnetic latitude, and vice versa (we’ve searched the internet up and down for simple calculators, but we haven’t found any, sorry).

Geomagnetic Storms and Aurora Visibility

The number one cause of auroras is geomagnetic storms.

These storms are a disturbance in the magnetosphere that surrounds the planet and is caused by the planet’s interaction with the highly charged solar winds. Whenever the conditions of the solar winds change in any way, they affect the earth’s magnetosphere causing storms that can last anywhere from several hours to several days. During this time period, the energy contained within the solar winds is transferred to the earth’s magnetosphere, resulting in the formation of the auroras.

The sun is known to follow a cycle of geomagnetic storms that peak every 11 years or so. While geomagnetic storms occur any time of the year, and at any point during a solar cycle, they are most active and frequent on peak years. When the cycle is at its peak, the amount of solar flares produced on a regular basis is at its greatest. As a result, more radiation is sent barreling out into space, which results in more auroras being created in our skies. Basically, this means that more auroras are visible during these solar cycle peak years.

How to Read Northern Lights Tracking & Forecast Tools

The vast majority of aurora forecasts are expressed using the Kp index. This index is used to identify disturbances in the Earth’s magnetic potential and is, therefore, a perfect way of determining the probability of the appearance of the auroras. As the Kp index increases, the potential for geomagnetic activity also increases. The higher the number, the further away from the poles the auroras can be seen.

Aurora Visibility Table based on Kp Index

*Source: https://www.swpc.noaa.gov/sites/default/files/images/u2/TheK-index.pdf

**The latitude at which aurora can be seen. Please be aware that the magnetic latitude is different from the geographic latitude, and there is no easy way to convert between the two. Figures rounded to closest whole number. Source: https://www.swpc.noaa.gov/content/tips-viewing-aurora

Technical Terms used in Forecasting & Tracking Northern Lights

When visiting an aurora forecasting site, the technical jargon can be quite overwhelming. However, there are only a few important things that the average person needs to know in order to understand how the appearance of the lights is forecasted.

Kp Index

The Kp index is the most important number to take into consideration when forecasting the auroras. This number ranges from zero and goes all the way up to nine, and represents the amount of disturbance in the Earth’s magnetosphere. As the turbulence in the solar winds increases, the disturbance within the Earth’s magnetic field also increases, thus bringing up the Kp index.

Not only does this number identify how powerful the auroras can be, but also helps to identify just how far away from the poles the auroras can be seen. Simply put, for those who are in the auroral oval, the auroras can appear with a Kp index of zero to one. However, as the index increases towards nine, the further away from the auroral oval that the northern lights can be viewed.

A Kp index of 9 can be seen as far as 45 degrees from the poles. During the peak of the last solar cycle, the aurora borealis was visible as far south as the 40th latitude, which meant that people as far south as Oregon, Idaho, Wyoming, Nebraska, Iowa, and even Missouri were able to view the elusive lights.

HPI

The term HPI comes up quite often on Aurora forecasting websites. HPI stands for “hemispherical power unit”, which is a measurement of the particle precipitation along the center of the auroral oval. On most forecasting websites, this number is actually indicated by either a green or red color, which does not mean that the auroras are visible, rather it refers to the potential of viewing them. When that green color forecasting turns red, there is a higher chance of viewing the elusive lights.

Near the map, you will usually find a chart that starts and stops at the solar terminators, which represent sunset and sunrise. This will allow you to determine roughly what time of night the potential for viewing the elusive lights is the highest. As a general rule of thumb, you will want to see an HPI of at least 90%.

Forecast Lead Time

Forecast lead time is an important factor when it comes to identifying the perfect locations to view the northern lights and southern lights. This lead time is based on a model referred to as OVATION, which is able to provide a 30-minute to 90-minute forecast, depending on the location. This lead time is specifically calculated based on the actual time it takes for the solar winds to travel to earth from the L1 observation point. Situated at this L1 observation point is the Solar and Heliospheric Observatory satellite, which is better known by the acronym SOHO. It is the nearest point from the planet that provides an on obstructed view of the sun.

Energy Deposition

It’s not uncommon when visiting an aurora forecasting website to hear references about energy deposition. But most sites offer very little explanation of what exactly this means. Energy deposition is the depositing of particles from the solar winds into the magnetosphere.

In order for the auroras to exist, there must be some form of a storm on the surface of the sun. This storm results in the creation of solar flares that fire highly energized particles out into space. These particles form the solar wind and eventually reach the planet’s atmosphere. It is the interaction of the earth’s atmosphere with these particles which create the plasma that we know as the auroras. The permeation of the upper atmosphere by the solar winds is what is most commonly referred to as energy deposition.

Websites for Forecasting & Tracking Northern Lights

National Oceanic and Atmospheric Administration

Website: https://www.swpc.noaa.gov/products/aurora-30-minute-forecast

Where: Worldwide

The National Oceanic and Atmospheric Administration is the scientific and regulatory division of the United States government that is responsible for monitoring the weather, oceans, and other natural phenomena including the aurora borealis. Not only do they provide a 30-minute forecast of the aurora borealis, but they also provide a forecast for the aurora australis.

University of Alaska

Website: https://www.gi.alaska.edu/monitors/aurora-forecast

Where: Alaska

The University of Alaska-Fairbanks is the de facto University responsible for monitoring and forecasting the appearance of the aurora borealis overtop of the state. They provide an excellent 30-minute forecast for anyone who is visiting Alaska in order to view the elusive lights.

University of Alberta

Website: https://www.aurorawatch.ca/

Where: Canada

If you are planning on visiting Canada in order to view the northern lights, then the University of Alberta’s Aurora Watch is the perfect destination for receiving up-to-date forecasts of the auroras. They provide a regularly updated 30-minute forecast for anyone seeking more information about the northern lights.

Icelandic Meteorology Office

Website: https://en.vedur.is/weather/forecasts/aurora/

Where: Iceland

When it comes to visiting Iceland, the best place to go for up-to-date information regarding the forecast of aurora over the country is the Icelandic Meteorology Office. The Icelandic Meteorology Office is responsible for monitoring the weather, oceans, and other natural phenomena around the country. They offer an excellent 30-minute forecast for the northern lights.

Norwegian Center for Space Weather

Website: https://site.uit.no/spaceweather

Where: Norway

The Norwegian Center for Space Weather is the de facto institution in Norway when it comes to monitoring the elusive Northern lights. As the government agency responsible for monitoring the weather over Norwegian skies, their forecast is updated regularly.

Bureau of Meteorology

Website: https://www.sws.bom.gov.au/Aurora

Where: Australia, Southern Hemisphere (Aurora Australis)

The Bureau of Meteorology is an Australian government entity that is responsible for monitoring the skies over the country. They are also the de facto authority to provide accurate forecasting of the appearance of the elusive aurora australis.

Parsec VZW – Belgium

Website: https://www.spaceweatherlive.com/en/auroral-activity/aurora-forecast.html

Where: Worldwide

Space Weather Live is a privately funded Aurora forecasting website that is based out of Belgium. Their forecasts are regularly updated, and provide information for the best viewing locations around the globe.

Aurora Labs

Website: https://www.auroralabsnorway.com/aurora-forecast.html

Where: Norway, Worldwide

The Aurora Labs is a popular, privately owned entity that provides regularly updated aurora forecasts for those visiting Norway as well as other popular destinations around the world. Their 30-minute forecast is very simple to read.

Final Thoughts on Aurora Borealis Forecast

This wraps up our guide to reading aurora borealis forecast and northern lights tracking guide. With this comprehensive guide, you should now have a very good idea of how to read an aurora forecast, to predict when and where to see the northern lights or southern lights.

Generally, the most popular website for checking the aurora borealis forecast in the northern hemisphere is National Oceanic and Atmospheric Administration (NOAA). In the southern hemisphere, head to the Bureau of Meteorology (BOM).

The most important value when reading the forecast is the Kp Index. If you want to spend the least possible time on learning the basics of reading an aurora forecast, focus your time on learning about Kp index and what it means, and you should be pretty good to go.

Happy aurora chasing!