GLOSSARY

Aurora Australis - the southern aurora, which forms in an oval centered on the south magnetic pole in Antarctica.

Aurora borealis - the northern aurora, which forms in an oval centered on the north magnetic pole in the artic.

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.

ionosphere - an upper layer of the atmosphere where many atoms lose one or more electrons, or are "ionized" by energy from sunlight each day.

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.

magnetosphere - the area surrounding the Earth containing the Earth's magnetic field, shaped by the interaction between the field and the solar wind

magnetotail - long, wake-like structure on the anti-sunward side of the Earth's magnetic field. The solar wind "drags" the Earth's field out for a distance many times earth's-radius into space.

plasma - a gas composed of energetic electrons and positive ions

positive ion - Any atom missing one or more of its electrons. In the case of a hydrogen atom, which has only one electron, the ion is simply a proton.

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.

solar wind - continuous outflow of solar magnetic field and subatomic particles from the solar atmosphere (corona) into the solar system

spectrum - the unique set of colors of light emitted by an atom or a compound when it absorbs energy, such as from light, heat, or electricity.

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.