auratransient

Auratransient refers to a brief, localized auroral-like emission in Earth's upper atmosphere. The term describes luminous events that brighten and fade within seconds to minutes and are smaller in area than typical auroral displays. These transients may appear as isolated patches, short arcs, or moving points embedded within a broader auroral structure. The name combines aurora with transient to emphasize their fleeting character.

Observational characteristics: Auratransients are most often detected during periods of enhanced geomagnetic activity and substorm growth. They can occur at high latitudes and sometimes at mid-latitudes during strong storms. They are typically observed with ground-based all-sky cameras, narrow-field imagers, spectrographs, and satellites; their short duration requires high-cadence observations. Color composition commonly includes green light from atomic oxygen and, less often, red or blue signatures depending on altitude and atmospheric composition.

Causes and mechanisms: The prevailing interpretation is transient enhancements in magnetosphere-to-ionosphere energy input, including brief bursts of energetic electron precipitation or field-aligned current reconfigurations. Such episodes can create localized increases in excitation of atmospheric constituents, yielding rapid brightening that propagates or flickers before fading.

Relation to other phenomena: Auratransients are distinct from persistent auroras by duration and spatial scale; they may be related to small-scale auroral arcs, patches, or discrete events within substorm dynamics. They are also unrelated to sprites or blue jets, which originate in different atmospheric layers and mechanisms.

See also: aurora, airglow, geomagnetic activity.