Sine Wave

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A RARE SINE WAVE IN THE MAGNETOSPHERE: Imagine you're at a hard rock concert. Waves of heavy metal crash against your eardrums, you can barely hear a thing, when, suddenly, the delicate trill of a flute cuts through the cacophony.

Something like that happened to Stuart Green of Lancashire UK during the severe geomagnetic storm of Oct. 10, 2024. "My backyard magnetogram was a riot," says Green. "But when I took a closer look, there was a delicate wave riding on top of the 'noise.'"

Green detected a rare "pulsation continuous"--or "Pc wave" for short. This is research jargon meaning, essentially, a pure sine wave in the magnetosphere. Pc waves are classified into 5 types depending on their frequency. Green's specimens are Pc1 and Pc2.

Usually, Pc waves are recorded only during periods of extreme quiet. They are delicate and hard to detect. Capturing one during riotous geomagnetic activity is extremely unusual. It is a testament to the sensitivity of Green's research-grade (albeit homemade) magnetometer--and the degree to which every mode of the magnetosphere was simultaneously activated by the Oct. 10th storm.

Zooming into Green's data shows the 7-to-8 second regularity of the waves

So what? These particular waves matter because they can help satellites survive severe space storms. Fast Pc1 and Pc2 waves scatter "killer electrons" out of the Van Allen radiation belts, making the region safer for satellites that orbit through the belts when they are supercharged by solar activity.

Would you like to monitor the magnetosphere for rare waves? Stuart Green's backyard magnetometer is a great DIY project. Here are his instructions.