The Sun threw a tantrum today, and Earth felt it almost instantly.
An X-class solar flare, the most powerful category of solar eruption on the books, fired off from the Sun’s surface and sent a furious wave of electromagnetic radiation hurtling toward Earth at the speed of light. The result: a strong radio blackout across the sunlit side of our planet.
WHAT IS AN X-CLASS SOLAR FLARE?
Think of the Sun as a pressure cooker. Now and then, tangled magnetic fields near dark patches on its surface, called sunspots, snap and release enormous bursts of energy. These are solar flares.
Scientists classify them from weakest to strongest: A, B, C, M, and X. Each step up the ladder is 10 times more powerful than the one before it. An X-class flare sits right at the top.
WHY DID THE RADIO GO SILENT?
Here is where it gets fascinating. The Sun’s flare did not just release light, it blasted out X-rays and extreme ultraviolet radiation, which travelled to Earth in roughly eight minutes.
When they arrived, they slammed into a specific layer of Earth’s upper atmosphere called the ionosphere, which is a vast shell of electrically charged particles that wraps around the planet between 60 and 1,000 kilometres above the surface.
Normally, high-frequency radio waves bounce off the ionosphere’s upper layers and travel great distances, much like how you can skip a stone across water.
This is how pilots, sailors, emergency services, and amateur radio operators communicate over vast stretches of the globe.
But during an X-class flare, something goes wrong. The radiation supercharges a lower, denser portion of the ionosphere called the D-layer.
Electrons in this layer begin colliding so frequently and violently that any radio wave passing through simply loses all its energy.
The signal does not bounce but gets swallowed. The result is a blackout.
HOW LONG DOES THE BLACKOUT LAST?
Typically anywhere from minutes to an hour, depending on the flare’s intensity. Only the sunlit side of Earth is affected, since the D-layer is charged by sunlight.
X-class flares sometimes also launch a coronal mass ejection, or CME, which is a colossal bubble of magnetised plasma that travels through space more slowly, arriving at Earth one to three days after the flare.
If one is on its way, geomagnetic storms could follow, potentially disrupting satellites, GPS systems, and even power grids.
For now, the lights are on, but your shortwave radio may have taken a brief, spectacular hit from the nearest star.
