Subauroral ion drift

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A subauroral ion drift (SAID), also known as a polarisation jet, is an

STEVE discovery paper[3] suggested the first link between this optical emission’s occurrence and that of an extremely fast and hot SAID event.[4]

SAIDs are observed equatorward of the auroral zone, at subauroral latitudes, typically in the local time sector between 18:00 hours and 22:00 hours.[1] They can occur individually, or as multiple events. SAIDs are characterised by a reduced density of ions, a strong westward flow, and an increased temperature. They can last between 30 minutes and 3 hours.[5] The exact characteristics of SAID events appear to have solar cycle, seasonal, and diurnal dependences.[6]

Although studied for decades, prior to the formal discovery of STEVE, SAIDs had never been associated with an optical emission.[7] STEVE was associated with a particularly extreme SAID, with a velocity over twice the norm and 100 K hotter.[7] STEVE has presented a new way for scientists, including citizen scientists, to study SAIDs.[8]

References

  1. ^
    doi:10.1029/GL006i008p00657
    .
  2. ^ Galperin, Y. I.; Ponomarov, Y. N.; Zosinova, A. G. (1973). "Direct measurements of ion drift velocity in the upper ionosphere during a magnetic storm". Cosmicheskie Issled. 11: 273.
  3. PMID 29546244
    .
  4. ^ Patel, Kasha (14 March 2018). "Mystery of Purple Lights in Sky Solved With Citizen Scientists' Help". NASA. Retrieved 17 May 2019.
  5. doi:10.1029/90JA02651
    .
  6. doi:10.1002/2014JA019807
    .
  7. ^ a b McRae, Mike. "Everyone, Meet 'Steve' – A Weird Type of Aurora We've Never Seen Before". ScienceAlert. Retrieved 17 May 2019.
  8. ^ Skibba, Ramin (15 March 2018). "Meet 'Steve,' a Totally New Kind of Aurora". National Geographic. National Geographic. Retrieved 17 May 2019.
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