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Module 1 of 6 · 6 min

The Sun has weather

The Sun doesn't just shine. It erupts, throwing billion-ton clouds of magnetized plasma into space. Those clouds are coronal mass ejections, and this is today's real catalog of them.

LiveToday's Sun. Every wedge is a real CME from the last 90 days.
Click any wedge to select it. The newest launched most recently, so it sits closest to the Sun.
1

The idea

A CME is matter. It takes one to three days to cross to Earth, and that travel time is the whole reason storms can be forecast. Its cousin the solar flare is light: here in eight minutes, no outrunning it. And most CMEs miss us entirely, because the Sun fires in every direction and Earth is a small target.

2

Your call

Click the newest CME on the map. Then read its label in the result below: how fast is it, and is it aimed at us?

Waiting for a click…

Check yourself · Module 1

1. A big solar flare and a CME erupt together. Which reaches Earth first?
The flare is radiation at light speed; the CME is matter that takes one to three days. That gap is the whole basis of storm forecasting.
2. Why can geomagnetic storms be forecast days ahead at all?
Coronagraphs see the eruption on day one; the plasma needs one to three days to arrive. The travel time is the warning time.
3. A fast CME launches pointed away from us. What happens at Earth?
Most CMEs miss. That's why the catalog marks each one Earth-directed or not: speed only matters if the aim is right.
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