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Alexandra Witze, Earth in action

When solar storms pummel Earth, there’s usually no need to panic

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SN Prime April 9, 2012 | Vol. 2, No. 14

If you can’t stand the heat, get out of the solar system.

The sun is just getting warmed up. That big thermonuclear ball is powering toward the peak of its 11-year cycle of activity, which should occur late next year. Solar storms are already starting to barrel in this direction, like those in February and March that lit up space weather warning systems across the planet.

Usually your biggest worry about the sun is whether it will be out in time for your picnic. But every decade or so, headlines start flaring with more dire forecasts: Solar storms are headed this way! The lights could go out! Cell phones might die! Astronauts need to take shelter!

All these solar-disaster predictions are a bit like worries over the Mayan calendar’s ending in 2012. Yes, sun storms are happening. But no, they’re not going to bring Armageddon, or rapture, or the day after tomorrow.

It’s true that the sun roils with a power that could annihilate all life on Earth. Blame it on the nuclear reactions that fuse hydrogen atoms in its heart, releasing torrents of energy. Four centuries ago, astronomers realized that this internal fire could also leave marks on the sun’s outsides. Galileo spent the summer of 1612 projecting the sun’s image through his newly made tele­scope and sketching the dark blotches he saw marching across the solar disk. He had discovered that the sun changes over time.

Those blobs, soon named sunspots, are a sign that something powerful is going on. Just as a mole on someone’s cheek might indicate that a deeper melanoma lies below, sunspots are but a surface symptom. They hint that magnetic energy twists and churns deep within, just waiting for the chance to be released. When it is, that part of the sun brightens suddenly, in a flash known as a solar flare. When the sun is active, it can spit off as many as several solar flares in a day.

Where sunspots and solar flares are rumbling, so too may be the biggest, baddest solar monsters of all: coronal mass ejections, or CMEs. In these, the sun’s equivalent of a hurricane, supercharged bubbles of plasma come roaring off the solar surface and into nearby space at a million miles an hour. Within hours the CME can expand to be wider than the sun itself, then blast its way past Mercury, Venus, Earth and into the rest of the solar system.

If a CME happens to erupt in our direction, things can go south quickly. When the plasma reaches Earth, it revs up currents already flowing in the planet’s protective magnetic sheath, jolting it like a swig of Red Bull. The surge of extra energy can enter electrical power systems, causing fluctuations as it travels across the power grid. In March 1989, a CME sent so much energy flowing across North America that it shut down the grid in Quebec, blacking out much of the province and shuttering its biggest airport. No wonder people want to duck when they hear a solar storm is coming.

Tracking the sun is the job of space weather experts, who’ve assembled a jaw-dropping array of rating scales for measuring solar blasts. There’s the S scale for solar radiation storms, in which high-speed protons threaten to damage astronauts’ body tissues. There’s R, for high-frequency radio blackouts caused by X-rays that could doom sailors’ communications. And there’s G for geomagnetic storms, like the one that shut down Quebec.

All these ABCs can obscure the fact that scientists have a far better understanding than ever of the sun’s fickle nature. These days, Sol has more people watching him than the contestants in the Hunger Games. A fleet of satellites scrutinizes him from Earth orbit, taking detailed pictures of every magnetic pimple and burp. Other spacecraft hover around a gravitationally stable point in space about 1.5 million kilometers upstream from Earth, where they can get a head start on measuring energetic particles that wash over that spot on their way here.

That’s why researchers know what space weather is coming and how it might affect your cell phone, your picnic or your baseball game. Emergency officials can then batten down the hatches, by switching off key components on satellites or switching on backup systems to control fluctuations in the power grid. We live in an interconnected world, where space and things in space shape our daily lives. Checking for the chance of CMEs is as smart a daily move as checking for the chance of rain.

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