When you hear the word “weather” you probably don’t think about streams of red-hot plasma swirling about in violent storms big enough to swallow a planet. In outer space, however, more than 99% of the mass of the ordinary matter in the universe exists as a red-hot ionized state of matter called a plasma. The body of plasma most important to our relatively cool, rocky Earth is the Sun. Space weather is created by the interplay of electrically conductive plasma and electrical and magnetic fields driven by the prodigious energy of the Sun.
The electricity we take for granted is distributed by enormous currents flowing in several-hundred-thousand miles of interconnected high-voltage wire that make up the power grid. Electricity in power plants is generated by rotating car-sized coils of wire in a magnetic field. The power grid includes huge loops of wire in the magnetic field of Earth and under certain circumstances the grid can act as its own generator. The magnetic field of Earth is relatively weak, but the area of a loop in the grid can be the size of a state or more. Anything that creates changes in the Earth’s magnetic field causes powerful surge currents to flow in the power grid. These surge currents can cause large-scale losses of electricity, or blackouts.
A spinning ball of conducting plasma, the Sun acts like a gigantic electromagnet.
Underneath the Sun’s “surface,” boiling motions tangle its magnetic fields and build up as much energy as trillions of atomic bombs in a single magnetic “knot.” When a “short circuit” releases the energy in one of these knots, gigatons of charged particles get blasted outward, such as in the video at right from NASA’s Solar Dynamics Observatory. Occasionally, a coronal mass ejection happens to point at Earth and some of those particles slam into our planet.
In 1989, a record-setting solar storm crippled the electrical grid in eastern Canada, leaving millions without power. To get advance warning of severe solar storms, NASA and the European Space Agency have several research spacecraft that constantly monitor the Sun. Someday this research will enable us to predict “space weather” just as we do ordinary weather.