aurora-, -aurora +

An aurora, or northern dawn, that occurs in the northern regions, or the North Pole, of the earth.

1. An operator controlled gating (turning a switch or transistor on and off) to eliminate undesirable radar returns from the aurora.
2. The use of digital or electrical methods in radar to eliminate or reject the target signals from all targets that are outside certain range limits.

The auroral emissions of the Northern Hemisphere or the Southern Hemisplhere which occur at higher than normal altitudes.

1. An atmospheric phenomenon consisting of bands of light caused by charged solar particles following the Earth's magnetic lines of force: An aurora is the most intense of the several luminous atmospheric lights appearing sometimes at night as streamers or bands of light that occur in the upper atmosphere over the middle and high latitudes and seen most often in the Artic and Antarctic regions.

An aurora is thought to be caused by charged particles from the sun entering the earth's magnetic field and stimulating molecules in the atmosphere.
2. When capitalized, it means the goddess of the dawn, or the first light of day: In Roman mythology, Aurora was the goddess of the dawn, however in Greek her name was Eos.

1. A reference to or characteristic of the dawn or the period of dusk before sunrise: "When we woke up in the morning, we could see a dim auroral glow in the sky."
2. Pertaining to or referring to the Aurora Borealis or the Aurora Australis.

A large increase of electric and radio wave density in the D-level of the atmosphere caused by electron-bombardment of the atmosphere during an aurora or a geomagnetic storm.

1. The polar regions within the auroral zones.
2. The areas surrounding the auroral poles which are lying between the poles and the auroral zones.

A strong current of electricity which flows through the auroral zone during a polar substorm.

A geomagnetic perturbation (confusion or disorder) lasting one to two hours, which tends to occur during a local post-midnight time.

The magnitude of the substorm is largest in the auroral zone and corresponds to an injection of charged particles from the magnetotail into the auroral oval.

Any of the various shapes of auroral emissions:

• Arcs, bands of arching light extending across the sky.
• Rays, beams of light, appearing singularly or in bundles.
• Draperies, sheets of light spreading across the sky.
• Crowns, rays which seem to emanate from a common point.
• Diffuse aurora, scattered cloud-like surfaces.

The percentage of nights on which an aurora is seen at a given location or place on earth, or on which one would be seen if clouds don't interfere.

An imaginary line which connects areas of equal auroral intensity or frequency that can be observed and averaged over a number of years.

A prominent green or red line which can be seen in the spectra of auroras which corresponds to certain forbidden transitions of the neutral oxygen atom.

An oval-shaped or a rounded-like-an-egg region, centered on the Northern magnetic pole or the Southern magnetic pole, within which auroral emissions take place.

The sites or points on the earth's surface at which the auroral isochasms are centered or coincide with the magnetic-axis poles of the geomagnetic field.

Isochasms are lines on a map or chart connecting points where auroras are observed with equal frequency.

A magnetic pole is either one of the two variable points on the earth's surface towards which a compass needle points.

The propagation or chain reaction of radio waves which are reflected from the aurora in the presence of unusual solar activity.