Editing Aurora (section)

=== Abnormal types ===

==== STEVE ====
In 2016, more than fifty [[citizen science]] observations described what was to them an unknown type of aurora which they named "[[Steve (atmospheric phenomenon)|STEVE]]", for "Strong Thermal Emission Velocity Enhancement". STEVE is not an aurora but is caused by a {{convert|25|km|mi|abbr=on}} wide ribbon of hot [[plasma (physics)|plasma]] at an altitude of {{convert|450|km|mi|abbr=on}}, with a temperature of {{convert|3000|C|K F|abbr=on}} and flowing at a speed of {{convert|6|km/s|mi/s|abbr=on}} (compared to {{convert|10|m/s|ft/s|abbr=on}} outside the ribbon).<ref>{{Cite news|url=https://phys.org/news/2018-08-kind-aurora.html|title=New kind of aurora is not an aurora at all|last=American Geophysical Union|date=20 August 2018|work=Phys.org|access-date=21 August 2018|archive-date=30 March 2022|archive-url=https://web.archive.org/web/20220330051224/https://phys.org/news/2018-08-kind-aurora.html|url-status=live}}</ref>

==== Picket-fence aurora ====

The processes that cause STEVE are also associated with a picket-fence aurora, although the latter can be seen without STEVE.<ref>{{cite web|last1=Andrews|first1=Robin George|title=Steve the odd 'aurora' revealed to be two sky shows in one|url=https://www.nationalgeographic.com/science/2019/05/odd-aurora-named-steve-revealed-to-be-two-different-sky-shows-in-one/|archive-url=https://web.archive.org/web/20190504000133/https://www.nationalgeographic.com/science/2019/05/odd-aurora-named-steve-revealed-to-be-two-different-sky-shows-in-one/|url-status=dead|archive-date=4 May 2019|website=National Geographic|access-date=4 May 2019|date=3 May 2019}}</ref><ref name="nishimura-2019">{{cite journal|last1=Nishimura|first1=Y.|last2=Gallardo-Lacourt|first2=B.|last3=Zou|first3=Y.|last4=Mishin|first4=E.|last5=Knudsen|first5=D. J.|last6=Donovan|first6=E. F.|last7=Angelopoulos|first7=V.|last8=Raybell|first8=R.|title=Magnetospheric signatures of STEVE: Implication for the magnetospheric energy source and inter-hemispheric conjugacy|journal=Geophysical Research Letters|volume=46|issue=11|pages=5637–5644|date=16 April 2019|doi=10.1029/2019GL082460|bibcode=2019GeoRL..46.5637N|doi-access=free }}</ref> It is an aurora because it is caused by the precipitation of electrons in the atmosphere but it appears outside the auroral oval,<ref>{{cite web|last1=Lipuma|first1=Lauren|title=Scientists discover what powers celestial phenomenon STEVE|url=https://news.agu.org/press-release/scientists-discover-what-powers-celestial-phenomenon-steve/|website=AGU News|publisher=American Geophysical Union|access-date=4 May 2019|archive-date=4 May 2019|archive-url=https://web.archive.org/web/20190504103127/https://news.agu.org/press-release/scientists-discover-what-powers-celestial-phenomenon-steve/|url-status=live}}</ref> closer to the [[equator]] than typical auroras.<ref>{{cite web|url=https://www.theguardian.com/science/shortcuts/2018/mar/19/steve-mystery-purple-aura-rivals-northern-lights-alberta-canada-nasa|title='Steve': the mystery purple aurora that rivals the northern lights|last=Saner|first=Emine|date=19 March 2018|website=The Guardian|language=en|access-date=22 March 2018|archive-date=22 March 2018|archive-url=https://web.archive.org/web/20180322013359/https://www.theguardian.com/science/shortcuts/2018/mar/19/steve-mystery-purple-aura-rivals-northern-lights-alberta-canada-nasa|url-status=live}}</ref> When the picket-fence aurora appears with STEVE, it is below.<ref name="nishimura-2019" />

==== Dune aurora ====

First reported in 2020,<ref>{{Cite journal|title=Citizen Scientists Discover a New Auroral Form: Dunes Provide Insight Into the Upper Atmosphere|url=https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019AV000133|journal=AGU Advances|year=2020|doi=10.1029/2019AV000133|last1=Palmroth|first1=M.|last2=Grandin|first2=M.|last3=Helin|first3=M.|last4=Koski|first4=P.|last5=Oksanen|first5=A.|last6=Glad|first6=M. A.|last7=Valonen|first7=R.|last8=Saari|first8=K.|last9=Bruus|first9=E.|last10=Norberg|first10=J.|last11=Viljanen|first11=A.|last12=Kauristie|first12=K.|last13=Verronen|first13=P. T.|volume=1|hdl=10138/322003|s2cid=213839228|hdl-access=free|access-date=22 May 2021|archive-date=22 May 2021|archive-url=https://web.archive.org/web/20210522031541/https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019AV000133|url-status=live}}</ref><ref>{{Cite journal|title=Citizen scientists discover a new form of the Northern Lights|url=https://phys.org/news/2020-01-citizen-scientists-northern.html|website=phys.org|access-date=22 May 2021|archive-date=22 May 2021|archive-url=https://web.archive.org/web/20210522031539/https://phys.org/news/2020-01-citizen-scientists-northern.html|url-status=live}}</ref> and confirmed in 2021,<ref name="grandin-2021">{{Cite journal|title=Large-Scale Dune Aurora Event Investigation Combining Citizen Scientists' Photographs and Spacecraft Observations|journal=AGU Advances|year=2021|doi=10.1029/2020AV000338|last1=Grandin|first1=Maxime|last2=Palmroth|first2=Minna|last3=Whipps|first3=Graeme|last4=Kalliokoski|first4=Milla|last5=Ferrier|first5=Mark|last6=Paxton|first6=Larry J.|last7=Mlynczak|first7=Martin G.|last8=Hilska|first8=Jukka|last9=Holmseth|first9=Knut|last10=Vinorum|first10=Kjetil|last11=Whenman|first11=Barry|volume=2|issue=2|pages=EGU21-5986|bibcode=2021EGUGA..23.5986G|doi-access=free}}</ref><ref>{{Cite news|title=Confirmation of an auroral phenomenon|url=https://phys.org/news/2021-05-auroral-phenomenon.html|website=phys.org|access-date=22 May 2021|archive-date=22 May 2021|archive-url=https://web.archive.org/web/20210522031540/https://phys.org/news/2021-05-auroral-phenomenon.html|url-status=live}}</ref> the dune aurora phenomenon was discovered<ref>{{cite web|url=http://blog.aurorasaurus.org/?p=1461|title=The discovery of the auroral dunes: How one thing led to another|website=Aurorasaurus|access-date=22 May 2021|archive-date=13 May 2021|archive-url=https://web.archive.org/web/20210513151346/http://blog.aurorasaurus.org/?p=1461|url-status=live}}</ref> by Finnish [[Citizen science|citizen scientists]]. It consists of regularly spaced, parallel stripes of brighter emission in the green diffuse aurora which gives the impression of sand dunes.<ref>{{cite web|url=https://www.youtube.com/watch?v=F6xM-XY6NYg| archive-url=https://ghostarchive.org/varchive/youtube/20211211/F6xM-XY6NYg| archive-date=11 December 2021| url-status=live|title=Revontulien 'dyynit', uusia löydöksiä – Aurora 'dunes' revisited|website=YouTube| date=4 May 2021}}{{cbignore}}</ref> The phenomenon is believed to be caused by the modulation of atomic oxygen density by a large-scale atmospheric wave travelling horizontally in a waveguide through an [[Inversion (meteorology)|inversion]] layer in the [[mesosphere]] in presence of [[electron precipitation]].<ref name="grandin-2021" />

==== Horse-collar aurora ====

Horse-collar auroras (HCA) are auroral features in which the auroral ellipse shifts poleward during the dawn and dusk portions and the polar cap becomes teardrop-shaped. They form during periods when the interplanetary magnetic field (IMF) is permanently northward, when the IMF clock angle is small. Their formation is associated with the closure of the magnetic flux at the top of the dayside magnetosphere by the double lobe reconnection (DLR). There are approximately 8 HCA events per month, with no seasonal dependence, and that the IMF must be within 30 degrees of northwards.<ref>{{Cite journal |last1=Bower |first1=G. E. |last2=Milan |first2=S. E. |last3=Paxton |first3=L. J. |last4=Anderson |first4=B. J. |date=May 2022 |title=Occurrence Statistics of Horse Collar Aurora |url=https://onlinelibrary.wiley.com/doi/10.1029/2022JA030385 |journal=Journal of Geophysical Research: Space Physics |language=en |volume=127 |issue=5 |doi=10.1029/2022JA030385 |bibcode=2022JGRA..12730385B |s2cid=248842161 |issn=2169-9380 |hdl=11250/3055028 |hdl-access=free |access-date=1 December 2022 |archive-date=12 May 2024 |archive-url=https://web.archive.org/web/20240512165217/https://agupubs.onlinelibrary.wiley.com/action/ajaxShowRecommended?widgetId=5cf4c79f-0ae9-4dc5-96ce-77f62de7ada9&ajax=true&doi=10.1029%2F2022JA030385&pbContext=%3BrequestedJournal%3Ajournal%3A21699402%3Bjournal%3Ajournal%3A21562202a%3Bpage%3Astring%3AArticle%2FChapter+View%3Bctype%3Astring%3AJournal+Content%3Bwebsite%3Awebsite%3Aagupubs%3Bissue%3Aissue%3Adoi%5C%3A10.1002%2Fjgra.v127.5%3Barticle%3Aarticle%3Adoi%5C%3A10.1029%2F2022JA030385%3Bwgroup%3Astring%3APublication+Websites%3BpageGroup%3Astring%3APublication+Pages%3BsubPage%3Astring%3AFull+Text&widgetKey=ux3-publicationContent-widget_5cf4c79f-0ae9-4dc5-96ce-77f62de7ada9_3067_144859_en&accordionHeadingWrapper=h2 |url-status=live }}</ref>

==== Conjugate auroras ====
Conjugate auroras are nearly exact mirror-image auroras found at [[conjugate points]] in the northern and southern hemispheres on the same geomagnetic field lines. These generally happen at the time of the [[equinox]]es, when there is little difference in the orientation of the north and south geomagnetic poles to the Sun. Attempts were made to image conjugate auroras by aircraft from Alaska and New Zealand in 1967, 1968, 1970, and 1971, with some success.<ref>{{cite book |title=The Aurora Watcher's Handbook |pages=117–124 |first=Neil |last=Davis |publisher=University of Alaska Press |date=1992 |isbn=0-912006-60-9 }}</ref>