Description

STEVE is an atmospheric phenomenon that appears as a purple and green light ribbon in th night sky.   The phenomenon is caused by a 25 km wide ribbon of hot plasma at an altitude of 450 km, with a temperature of 3,000 C and flowing at a speed of 6 km/s.  The phenomenon is not rare but had not been investigated prior to 2016.

Cause and association with "Picket Fence" aurora

The STEVE phenomenon accompanies a subauroral ion drift (SAID), a fast moving steam of extremely hot particles, and is thought to be generated in the ionosphere. 

STEVE phenomena is usually observed above a green "picket fence" aurora. These phenomena appear in both hemispheres simultaneously. The phenomenon is unpredictable and is of relatively short duration, lasting from 20 minutes to one hour.

[Image of a STEVE phenomenon taken at the Little Bow resort, AB, Canada on 17 August 2015,by  Elfiehall. Source: Wikicommons] 

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