What is a geomagnetic storm?

What is a geomagnetic storm?

What is a geomagnetic storm?

Answers to your questions about the news.
Oct. 24 2003 2:24 PM

Geomagnetic Storms

A strong geomagnetic storm is slated to hit Earth today, and experts warn that power grids and satellites could suffer. What's a geomagnetic storm?

Think of it as an electrical kick in the pants, courtesy of the sun. Geomagnetic storms like today's begin with an event called a coronal mass ejection, a geyser of solar gas. A CME can spout billions of tons of this ionized gas, also known as plasma, traveling at upwards of 3 million miles per hour. That discharge is carried the 93 million miles toward Earth by the solar wind, a constant stream of particles emitted by the sun.


Normally, when solar particles reach the Earth, they're deflected by the magnetosphere, the magnetic field produced by the planet. But in the wake of a major CME, the solar wind carries far too many ionized particles for the magnetosphere to handle. Charged particles slip through the defenses, so to speak, causing the magnetosphere to fluctuate. This produces an intensified ring current, an electrical current trapped within the magnetosphere. The intensity is so strong, in fact, that it can create electrical current in voltage transformers and other power-grid hardware. That's bad news for whomever manages those grids, as the resulting power surge can knock out service to millions of customers. Geomagnetic-storm watchers warily mention March 13, 1989, when 6 million customers of Hydro-Québec lost power for an extended time.

The good news is that geomagnetic storms can also produce brilliant light shows akin to the aurora borealis, or "northern lights." (Or, in the southern hemisphere, the aurora australis.) These lights are caused by milder, more common versions of today's storm and are visible in areas relatively close to the two magnetic poles. The abundance of charged particles that will be pounding the magnetosphere today should make for some great skywatching, at least for those lucky enough to live near the roof or the basement of the globe. However, the intensity of this particular storm may mean that people farther south may get a peek, too; the infamous 1989 storm was reportedly visible in Mexico.

Bonus Explainer: A few fringe scientists have speculated that there's a link between geomagnetic activity and mental health, arguing that psychiatric admissions increase during heavy storms. The mainstream dismisses this correlation as no more substantiated than reports that the full moon causes people to act strangely.

Explainer thanks the American Geophysical Union.