A phenomenon consisting of luminous colorful arcs, rays, and streamers that appear in a planet's upper atmosphere during the night with the greatest frequency in the northern and southern polar magnet
ic zones. This non-thermal radiation is caused by the emission of light from atoms excited by electrons accelerated along the planet's magnetic field lines at the magnetic poles. Fluorescent emission from atomic oxygen at 5557 Å results in a greenish glow, and there is a weaker effect from the red line at 6300 Å. Blue and purple colors are emitted by atomic and molecular nitrogen.
usually refers to visible aurora and the particles that create them, but may also refer to electrical currents that flow in the auroral region. One measure of auroral activity is hemispheric power
Characterized by more or less continuous lower border. They appear like a ribbon or sheet of luminosity, inclined in the direction of the magnetic field. They may be homogeneous, rayed, or striated, a
nd can be single or multiple.
An elliptical band around each geomagnetic pole ranging from about 75 degrees magnetic latitude at local noon to about 67 degrees magnetic latitude at midnight under average conditions. Those location
s experience the maximum occurrence of aurorae. The aurora widens to both higher and lower latitudes during the expansion phase of a magnetic substorm.
An oval-shaped distribution of the aurora. The oval is asymmetrical, but generally around the region of the Arctic and Antarctic. The oval increases in intensity and size when auroral activity is more
intense.
A form of the aurora consisting of rays or shafts of luminosity aligned in the direction of the geomagnetic field. It can consist of a single ray, a small bundle of rays, or many scattered rays.