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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

  05 Aug 2020

05 Aug 2020

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This preprint is currently under review for the journal ANGEO.

Fragmented Aurora-like Emissions (FAEs) as a new type of aurora-like phenomenon

Joshua Dreyer1,2, Noora Partamies3,4, Daniel Whiter5, Pål G. Ellingsen6, Lisa Baddeley3,4, and Stephan S. Buchert1 Joshua Dreyer et al.
  • 1IRF Swedish Institute for Space Physics, Space Plasma Physics group, Uppsala, Sweden
  • 2Uppsala University, Department of Physics and Astronomy, Uppsala, Sweden
  • 3The University Centre in Svalbard, Longyearbyen, Norway
  • 4Birkeland Centre for Space Science, Bergen, Norway
  • 5University of Southampton, Southampton, UK
  • 6UiT The Arctic University of Norway, Department of Electrical Engineering, Narvik, Norway

Abstract. This study analyses the observations of a new type of small-scale aurora-like feature, which is further referred to as Fragmented Aurora-like Emission(s) (FAEs). An all-sky camera captured these FAEs on three separate occasions in 2015 and 2017 at the Kjell-Henriksen Observatory near the arctic town of Longyearyben, Svalbard. A total of 305 FAE candidates were identified with varying degrees of certainty. They seem to appear in two categories – randomly occurring individual FAEs and wave-like structures with regular spacing between FAEs alongside auroral arcs. FAEs show horizontal sizes typically below 20 km, a lack of field-aligned emission extent and short lifetimes of less than a minute. Emissions were observed at the 557.7 nm line of atomic oxygen and at 673.0 nm (N2, first positive band system), but not at the 427.8 nm emission of N2+ or the 777.4 nm line of atomic oxygen. This suggests a limit to the energy of the generating mechanism. Their lack of field-aligned extent indicates a different generation mechanism than for aurora, which is caused by particle precipitation. Instead, these FAEs could be the result of excitation by thermal ionospheric electrons. FAE observations are seemingly accompanied by elevated electron temperatures between 110–120 km and increased ion temperatures at F-region altitudes. One possible explanation for this are Farley-Buneman instabilities of strong local currents. We provide an overview of the observations and discuss them as well as potential generation mechanisms in the present study.

Joshua Dreyer et al.

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Joshua Dreyer et al.

Video supplement

Auroral Structure and Kinetics video observations from Longyearbyen, Svalbard, 2015/12/07, 18:23UT Daniel Whiter

Joshua Dreyer et al.


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Latest update: 27 Sep 2020
Publications Copernicus
Short summary
We present observations of a new type of small-scale aurora-like feature, which we name Fragmented Aurora-like Emissions (FAEs). Whereas aurora is caused by particle precipitation, FAEs seem to be locally generated in the ionosphere, hence the term aurora-like. We analyse data from multiple instruments located near Longyearbyen on Svalbard to derive the main characteristics of FAEs. They seem to occur as two types within a narrow altitude region – individually or in regularly spaced groups.
We present observations of a new type of small-scale aurora-like feature, which we name...