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Magnetic storms are caused by solar flares and coronal mass ejections, and can disrupt communication and navigation systems, cause power outages, and damage satellites. Severe storms occur once a decade and can be dangerous to unshielded astronauts. The largest storm on record occurred in 1859, and a more recent storm in 1989 caused significant damage to infrastructure.
A magnetic storm is a disturbance in the Earth’s magnetic field caused by coronal mass ejections (CMEs) or solar flares from the Sun. It usually begins between 24 and 36 hours after the solar event, when a solar reaches the earth’s ionosphere. The storm typically lasts 24 to 48 hours, although some can last up to days. The effects of such a storm include disruption of communications and navigation systems, intense auroras, damage to satellites and during the most extreme storms, induced currents in power lines and pipelines causing power outages, and corrosion.
Severe magnetic storms occur about once every decade, with the most severe occurring once every century. They occur when energetic particles from a solar storm collide with the ionosphere and magnetosphere, creating a cascade of energetic particles and disturbing the atmosphere’s magnetic and electrical currents. There have been two strong magnetic storms in the past two centuries, including a storm from August 28 to September 2, 1859, which is the largest on record, and another on March 13, 1989.
During the magnetic storm of August 28 – September 2, 1859, auroras were seen as far south as Mexico, Cuba, Hawaii, and Italy. Telegraph wires in Europe and North America shorted, some causing fires. Active sunspots were observed on the Sun just 18 hours before the shock wave arrived, which triggered the geomagnetic storm. This is one of the first times a geomagnetic storm has been predicted in advance. The event became known as the solar superstorm of 1859.
A more recent magnetic storm, which occurred on March 13, 1989, was more damaging to the world’s infrastructure due to its greater infrastructure overall, as well as greater reliance on sensitive electronics, including satellites. The storm caused Hydro-Québec’s power grid to collapse in seconds, as induced currents in the wires detonated transformer cores and fried protective devices, causing a chain reaction that resulted in a loss of power for six million people for nine hours and substantial economic damage. The Toronto Stock Exchange had to be temporarily closed due to computer damage sustained by the magnetic storm. Several satellites in orbit were damaged at a cost of several tens of millions of dollars.
A magnetic storm could be particularly dangerous to unshielded astronauts, not because of the current induced in Earth’s magnetic field, but because of energetic particles coming directly from the sun itself. An astronaut in a conventional space suit on the surface of the Moon during a severe storm could receive 7,000 rem of radiation, a lethal dose. If the astronaut could be warned and take cover under the lunar soil, however, the effect would be minimal.
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