3 August 2010

Sun-storm to hit within 24 hours

by Kate Melville

Sky watchers might get to enjoy some spectacular Northern Lights tomorrow, thanks to a massive explosion on the surface of the Sun that blasted a huge quantity of plasma directly at the Earth.

The eruption, known as a coronal mass ejection, occurred early on Sunday morning and may herald a new period of instability for the Sun (the activity cycle of the Sun is about 11 years long on average). "This eruption is directed right at us, and is expected to get here early in the day on August 4th," said astronomer Leon Golub of the Harvard-Smithsonian Center for Astrophysics. "It's the first major Earth-directed eruption in quite some time."

The eruption was caught on camera by NASA's Solar Dynamics Observatory, launched in February. "We got a beautiful view of this eruption," said Golub. "And there might be more beautiful views to come, if it triggers aurorae."

When a coronal mass ejection reaches Earth, it interacts with our planet's magnetic field, potentially creating a geomagnetic storm. Solar particles stream down the field lines toward Earth's poles. Those particles collide with atoms of nitrogen and oxygen in the atmosphere, which then glow like miniature neon signs.

Aurorae normally are visible only at high latitudes, but during a geomagnetic storm they can light up the sky at lower latitudes. Sky watchers in the northern U.S. and other countries should look toward the north on the evening of August 3rd/4th for rippling "curtains" of green and red light.

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Source: Harvard-Smithsonian Center for Astrophysics