Northern lights over Calgary houses Andrew Seto
UCalgary physicist Eric Donovan explains the science behind the night-time illuminations amidst 2025 solar maximum
Last year, the night skies treated Calgarians to more auroral displays than usual. Space physicists say the best could be yet to come , with 2025 providing peak northern lights action thanks to the solar maximum in the sun’s 11 year cycle.
Dr. Eric Donovan , PhD, a University of Calgary physics professor and key researcher behind the discovery of the celestial phenomenon known as STEVE , unpacks that mystery and more in this Q and A.
How can I increase my chances of seeing the northern lights?
Part of it is lifestyle. I moved here 30 years ago and have seen the aurora 50 to 100 times, often after late nights as a junior faculty member. If you’re outside around 11 p.m. or midnight in the city’s north and spot green on the horizon, it’s likely the northern lights.
It’s good to go north, places like Yellowknife, Whitehorse or Churchill are best if it’s on your bucket list. When flying to Europe or Asia, I book a window seat on the left heading there or the right coming back. I’ve seen stunning auroral displays over Greenland and the North Atlantic.
Why are we seeing more northern lights in recent years?
The aurora forms when solar wind - ionized gas from the sun - interacts with Earth’s magnetic field, transferring energy that creates the northern lights.
Solar wind is stronger during the sun’s 11 year cycle peak, known as solar maximum. Since last year, this phase has brought three or four auroral displays that I’d call once-in-a-lifetime events.
When was the last solar maximum?
The last solar maximum was around 2014, as the solar cycle is approximately 11 years. Previous maxima were in 2003 and 1992. Each solar maximum varies in intensity, and this current cycle is particularly strong.
Do the northern lights make any sound?
The aurora has no known way to physically produce sound that reaches the ground, but about a third of people report hearing it. Strangely, their descriptions are similar worldwide. We haven’t been able to record anything, but maybe it could be explained by synesthesia, a blending of senses or static discharge affecting objects like pine needles.
Why are the northern lights more well-known than the southern lights (aurora australis)?
More people live near the northern aurora in Canada, Alaska and Northern Europe. The auroral oval in the Southern Hemisphere mostly covers Antarctica, where fewer people can see it. Northern countries also promote the northern lights culturally and through tourism.
What causes the different colours in the northern lights?
The colours are produced by particles from space colliding with atoms and molecules in the Earth’s atmosphere. Spectral lines of green and red come from varying transitions of atomic oxygen, while the violet along the bottom of auroral arcs comes from molecular transitions in nitrogen. The different colours are a consequence of the mechanical way the light is made. Early scientists used these colours to understand the composition of the upper atmosphere.
What is STEVE, and how is it different from the northern lights?
STEVE (Strong Thermal Emission Velocity Enhancement) appears as a mauve ribbon of light and is caused by a strong electric field driving fast-moving ionized gas. Unlike the northern lights, STEVE is not caused by particles from space hitting the atmosphere. Whether STEVE is considered aurora is still debated in the scientific community.
