auroral oval - the oval, centered on a magnetic pole, where auroral activity takes place. At any time, the limits of the ring depend on conditions such as the number and energy of electrons in the aurora.
coronal mass ejection (CME) - violent eruption of a large bubble in the Sun's outer corona, which sends huge amounts of ionized gas (particles) into the solar wind. An average CME releases a mass of particles equivalent to a mountain.
geomagnetic substorm - disruption in the Earth's inner magnetosphere caused by the impact of intense solar winds, such as those caused by flares and CME's. Storms can cause power outages, interfere with radio communications, and pose a health hazard to astronauts working in space.
magnetic poles - two spots on the northern and southern hemispheres that are situated over the magnetic poles of the Earth's core. A compass needle points to the north magnetic pole. In contrast, the geographic poles are surface points located on the Earth's axis of rotation.
solar flare - a sudden outburst of energy and matter from the Sun. Flares can release more energy than billions of tons of TNT (hydrogen bombs are measured in megatons: millions of tons!) in a matter of seconds or minutes.
sunspots - areas of concentrated magnetic field on the surface of the sun, which appear dark in visible light images. These regions are really the "footprints" of magnetic field lines that can erupt into flares or coronal mass ejections.