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Northern Lights are often difficult to predict
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Northern Lights are often difficult to predict

There are a lot of predictions floating around about the Northern Lights this coming weekend and there is indeed a better than normal chance that we will see them in parts of New England.

But even with a higher-than-average level of confidence in seeing these spectacular displays of shimmering light, aurorae are still notoriously difficult to predict. To understand why there is so much uncertainty, it is important to understand the mechanisms behind what causes the aurora borealis.

The Earth is surrounded by a magnetic field known as the magnetosphere. This field protects our atmosphere from the solar wind that continually bombards Earth at an average speed of 1 million miles per hour – sometimes faster, sometimes slower, but often steady. This solar wind consists of plasma that comes from the sun and travels through our solar system and even beyond Pluto.

The solar wind itself is not consistent, and as the sun goes through periods of high and low activity (a solar cycle), the solar wind varies approximately every eleven years.

Sometimes the sun spews out a lot of energy in a solar storm known as coronal mass ejection, or CME. When these occur, the solar wind rushes toward Earth with more energy. That energy then interacts with the Earth’s magnetic field, disrupting and reconfiguring its regularity. Cracks in the field open and close as the Sun’s and Earth’s magnetic fields connect.

As the various elements in Earth’s atmosphere fluoresce, they produce a dazzling display of colors green, red, purple, pink and even blue, known as the Northern Lights, or aurora borealis (the Southern Lights or aurora australis in the Southern Hemisphere). . NASA’s Magnetospheric Multiscale Mission was launched nearly a decade ago to observe the reconnections of electrons in the magnetosphere and help us better understand and predict this space weather.

The relationship between the sun and Earth’s atmosphere is complex.NASA

With this in mind, let’s get back to this weekend’s aurora forecast. During a storm, when winds are forecast to be gusty, gusts are sometimes stronger or weaker than predicted. These gusts will occur at relatively random intervals during a storm.

For example, no one can predict that there will be gusts of wind during a storm at 11:07 am. We often say that the strongest gusts are likely to occur within a certain time frame, but it is still a random thing. After a CME has occurred, space weather forecasters use various tools to predict when these solar wind gusts are likely to interact with the magnetosphere, but which part of the magnetosphere is most charged and the intensity and placement of geomagnetic storms and substorms are often difficult to distinguish. .

The Northern Lights flash in the sky above a farm in Brunswick, Maine, on May 10, 2024. Robert F. Bukaty/Associated Press

Additionally, a storm could occur over another part of the planet while we are in daylight, or cloud cover could obscure the view of a storm overhead.

I first saw the Northern Lights in the summer of 1981 in Maine. It’s a sight I’ve had the pleasure of observing several times since and it never disappoints. Keep an eye on social media this weekend and look up. If you’re lucky, you might witness one of nature’s grandest scenes.

But of course no promises.