Solar Flares and the Northern Lights: Understanding What's Actually Connected

Solar flares get a lot of attention in aurora coverage, and the association makes intuitive sense — a dramatic eruption on the sun ought to produce a dramatic display in the sky. The reality is more specific than that, and understanding the distinction between what a solar flare does and what it doesn't do will make you a better reader of space weather forecasts.

What a Solar Flare Is

A solar flare is a sudden, intense burst of electromagnetic radiation from the sun's surface, typically originating from active regions with complex sunspot groups. The energy released in a large flare is enormous — equivalent to billions of nuclear bombs — but it's expressed as radiation: X-rays, ultraviolet light, and radio waves, not as a cloud of plasma traveling through space.

What helped me keep this straight: think of a solar flare as the flash from a camera. It reaches you almost instantly — in the case of the sun, the radiation arrives at Earth in about eight minutes — and it's gone. A coronal mass ejection, by contrast, is more like someone throwing a bucket of water at you from across the room. It takes time to arrive, but when it does, it hits with sustained force. Flares and CMEs often happen together, but they are different phenomena with different effects.

For the broader picture of how these events fit into solar activity cycles, see our overview of solar cycles and the northern lights.

What Solar Flares Actually Do — and Don't Do — for Aurora

Here's the part that surprises many aurora travelers: solar flares do not directly cause aurora in the way that coronal mass ejections do. The electromagnetic radiation from a flare doesn't carry the charged particles needed to excite atmospheric gases and produce visible light in the way that CME-driven particle precipitation does.

What flares do is two things. First, they often signal that an active region on the sun is energetic enough to also produce a CME — so a large flare is worth paying attention to as a potential precursor. Second, the radiation from a major flare can ionize Earth's upper atmosphere on the sunlit side, temporarily disrupting radio communications and GPS signals. This is called a solar radiation storm and is a separate effect from aurora.

The aurora connection comes when a CME accompanies the flare — which is common but not guaranteed. When a CME follows a large flare and is directed toward Earth, the combination can produce significant geomagnetic activity 1 to 3 days later. That's the scenario aurora travelers and photographers are actually hoping for when they see a major flare reported in the news.

Being in the right place when that activity arrives is what our Northern Lights Tour in Fairbanks is built around — positioning guests beneath the auroral oval during the active season with guides monitoring conditions each night. For timing considerations, see our guide on the best time to see the northern lights in Alaska.

Solar Flare Classification

Flares are classified by their X-ray intensity on a lettered scale: A, B, C, M, and X, with X being the most intense. Within each class, a number refines the intensity — an X2 flare is twice as powerful as an X1. M-class flares are moderate; X-class flares are major events. The classification gives a rough sense of how energetic the source region is, which informs the probability that a significant CME accompanied the flare.

What Solar Flares Mean for Photographers

For aurora photographers, the immediate effect of a solar flare is minimal — the radiation arrives and dissipates within minutes, long before any associated geomagnetic activity develops. The more relevant signal is what a large flare implies about the next 1 to 3 days. An X-class flare from an Earth-facing active region is a credible reason to pay closer attention to CME forecasts and NOAA storm watches in the days that follow.

One indirect effect worth knowing: major solar radiation storms accompanying large flares can degrade GPS accuracy temporarily. For photographers relying on GPS for location tagging or navigation to remote shooting sites, this is a practical consideration during periods of intense solar activity — though it's rarely severe enough to cause significant problems for ground-based navigation.

The practical takeaway: when you see a report of a large solar flare, check whether a CME was also observed and whether it's Earth-directed. That follow-up question is the one that determines whether the flare is relevant to your aurora plans.

Return to the full Northern Lights Glossary to continue through the Solar Physics and Space Weather section.