How to Predict Auroral Events in the Northwest Territories
Forecasting the aurora above communities in southern Canada and the United States can be tricky, but in the North it is actually much easier to predict the aurora than it is to predict the weather. Amateur space weather enthusiasts in the North can quickly learn how to make a prediction simply by monitoring a few key websites, and by adjusting global predictions with the actual observations made above or near your community.
First, let’s start with the basics. There are many contributing factors that determine the brightness and duration of auroral events. And while there is no exact method to determine exactly when an aurora will appear in the sky, there are many ways to predict the intensity and the duration of auroral events in the North, and, subsequently, predict the potential for a powerful surge of auroras to appear in southern Canada and the United States.
An excellent starting point for making an auroral prediction is by researching the current and forecasted space weather conditions, which are monitored by the National Oceanic and Atmospheric Administration (NOAA), the same organization that monitors hurricane activity in the United States (among other things, of course). There are two very important NOAA space weather websites to assist you, the Space Weather Prediction Center, and the 3-Day Report on Solar and Geophysical Activity. The other very important website for viewing up-to-the minute news and information on solar and geomagnetic activity is the “NASA Space Weather Bureau” website, spaceweather.com.
Next, it is important to learn about the proximity of your community to the aurora oval, a ring of geomagnetic activity that is best described as Earth’s auroral mailbox – when a package of charged particles arrives from the Sun, those communities that are beneath the oval will be getting a colourful message from above. As the night progresses, communities further south and further north may also receive a similar message. (TIP: The most likely place to look for auroras is along the outer edge of the oval, which is constantly expanding and contracting based on the arrival of incoming particles).
A great way to determine if you are in the Polar, Auroral, or Sub-Auroral zone is to visit the Space Weather Canada website. A three zone forecast is calculated based on the relative position of the auroral oval and the potential for geomagnetic activity that will result from current space weather conditions.
Generally, those communities located between 60-64°N latitude will spend a majority of each night positioned directly beneath the auroral oval. Communities further south (55-59°N latitude) often can see the glow of auroras when they look north, and can expect that a moderate increase in solar activity will actually cause the oval to expand southward (much like a rubber band, the oval expands and contracts frequently) and therefore change the position of the auroras from the horizon to overhead.
Communities that are even further south require signifcant geomagnetic events to spark auroras in their skies, but as the Sun becomes active, the possibility of major auroral events increases. On average this means communities in southern Canada and the United States can expect to see auroras a few times every year.
There are other some other factors to consider when formulating a northern sky aurora forecast. As an example, though the sun is often the most significant source of auroras in the South, communities between 60-64°N latitude will still see auroras almost every dark night, even when the Sun and space weather conditions are calm. To try and explain why this is occurring, scientists focus on the particles trapped in an area of Earth’s magnetic field known as the plasma sheet (see “An avalanche model of magnetospheric substorms…” for an example of the work being done at the University of Calgary). The Earth itself is also believed to be a source of charged particles, and dynamic and energetic reconnections that occur in Earth’s magnetic field (in particular the magnetotail) are a major contributor to auroral events that are not directly linked to solar events.
Roughly translated, this means in the North it is very rare that you will see NOTHING in the sky over the course of 24 hours. In Yellowknife, located at 62° North, the only way that there will be no auroras in your future is if you choose not to look up.
So, in order to become an aurora forecaster for your community, start by monitoring the Sun, the space weather environment and the global aurora forecast. Next, go outside and watch the sky. With enough observation and prediction practice, your forecast will reflect your knowledge of the potential for auroras at your latitude, and will demonstrate you have a strong understanding of your local sky.
Yellowknife Aurora Forecast 101
The Yellowknife Aurora Forecast predicts the intensity and frequency of auroras above Yellowknife from dusk until dawn, and categorizes the full night of auroras using a 10-point Activity Level system.
To make a prediction, four important variables are considered – variables that are known to influence auroras on Earth:
1. The intensity of incoming solar wind (0-3);
2. The density of the incoming solar wind (0-3);
3. The anticipated magnetic field flux when solar wind reaches Earth (0-3); and
4. The atmospheric conditions above Yellowknife (0-1)
In order to research each variable, the forecaster requires access to the latest space weather data. A variety of websites are used that provide both real time access to activity on the Sun, as well as the latest magnetic field and solar wind monitoring information.
Predicting the intensity of the aurora estimates how bright the aurora will be when the solar particles collide with gases in Earth’s atmosphere. The faster the solar wind, the more intense each peak of activity will be. Frequency forecasting estimates if the aurora will appear in the sky all night, most of the night, some of the night, or not at all.
• The Yellowknife Aurora Forecast was launched by volunteers in 2005 by Astronomy North to give families living between 60-64° North latitude advanced notice of auroral activity, much like announcing an upcoming fireworks show.
• The forecast was also designed to provide visitors with information about the skies in advance of their trip to the Northwest Territories. Auroras above Yellowknife attract thousands of tourists and millions of dollars to the Northwest Territories every year, making the capital one of only a few communities on Earth where the sky has an impact on the economy.
• Astronomy North’s aurora forecast was the first community specific aurora forecast in the world. Most forecasts provide a global aurora forecast, or a northern hemisphere forecast. New community-specific forecasts are emerging in locations where the auroras are not as common, such as Edmonton.
• Yellowknife is the largest Canadian community found directly beneath the aurora oval, a location where geomagnetic activity is as common as rainfall in Vancouver, snowfall in Iqaluit, fog in St. John’s, or sunshine in Florida.
• A prediction made for Yellowknife is also applicable to any community located between 60-64° North latitude.
