Articles | Volume 39, issue 6
https://doi.org/10.5194/angeo-39-975-2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/angeo-39-975-2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Regular paper
| 
25 Nov 2021
Regular paper |
| 25 Nov 2021
| 25 Nov 2021
Fine-scale dynamics of fragmented aurora-like emissions
Physics and Astronomy, University of Southampton, Southampton, United Kingdom
Hanna Sundberg
Swedish Defence Research Agency (FOI), Stockholm, Sweden
Betty S. Lanchester
Physics and Astronomy, University of Southampton, Southampton, United Kingdom
Joshua Dreyer
Swedish Institute of Space Physics (IRF), Uppsala, Sweden
Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden
Noora Partamies
University Centre in Svalbard (UNIS), Longyearbyen, Norway
Birkeland Centre for Space Science, Bergen, Norway
Nickolay Ivchenko
School of Electrical Engineering and Computer Science, Royal Institute of Technology (KTH), Stockholm, Sweden
Marco Zaccaria Di Fraia
citizen scientist
Rosie Oliver
citizen scientist
Amanda Serpell-Stevens
citizen scientist
Tiffany Shaw-Diaz
citizen scientist
Thomas Braunersreuther
citizen scientist
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Ann. Geophys., 39, 189–237, https://doi.org/10.5194/angeo-39-189-2021, https://doi.org/10.5194/angeo-39-189-2021, 2021
Short summary
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This is a review paper that summarises the current understanding of the lower thermosphere–ionosphere (LTI) in terms of measurements and modelling. The LTI is the transition region between space and the atmosphere and as such of tremendous importance to both the domains of space and atmosphere. The paper also serves as the background for European Space Agency Earth Explorer 10 candidate mission Daedalus.
Cited articles
Aikio, A. T., Opgenoorth, H. J., Persson, M. A. L., and Kaila, K. U.:
Ground-based measurements of an arc-associated electric field, J. Atmos.
Terr. Phys., 55, 797–808, https://doi.org/10.1016/0021-9169(93)90021-P, 1993. a
Archer, W. E., Gallardo-Lacourt, B., Perry, G. W., St.-Maurice, J. P., Buchert,
S. C., and Donovan, E.: Steve: The Optical Signature of Intense Subauroral
Ion Drifts, Geophys. Res. Lett., 46, 6279–6286, https://doi.org/10.1029/2019GL082687,
2019. a
Ashrafi, M., Lanchester, B. S., Lummerzheim, D., Ivchenko, N., and Jokiaho, O.: Modelling of N21P emission rates in aurora using various cross sections for excitation, Ann. Geophys., 27, 2545–2553, https://doi.org/10.5194/angeo-27-2545-2009, 2009. a
Bahcivan, H.: Plasma wave heating during extreme electric fields in the
high-latitude E region, Geophys. Res. Lett., 34, L15106, https://doi.org/10.1029/2006GL029236,
2006. a
Buchert, S. C., Tsuda, T., Fujii, R., and Nozawa, S.: The Pedersen current carried by electrons: a non-linear response of the ionosphere to magnetospheric forcing, Ann. Geophys., 26, 2837–2844, https://doi.org/10.5194/angeo-26-2837-2008, 2008. a, b
Carlson, H. C., Oksavik, K., and Moen, J. I.: Thermally excited 630.0 nm
O(1D) emission in the cusp: A frequent high-altitude transient signature,
J. Geophys. Res., 118, 5842–5852, https://doi.org/10.1002/jgra.50516, 2013. a
Codrescu, M. V., Fuller-Rowell, T. J., and Foster, J. C.: On the importance of
E-field variability for Joule heating in the high-latitude thermosphere,
Geophys. Res. Lett., 22, 2393–2396, https://doi.org/10.1029/95GL01909, 1995. a
Dahlgren, H., Gustavsson, B., Lanchester, B. S., Ivchenko, N., Brändström, U., Whiter, D. K., Sergienko, T., Sandahl, I., and Marklund, G.: Energy and flux variations across thin auroral arcs, Ann. Geophys., 29, 1699–1712, https://doi.org/10.5194/angeo-29-1699-2011, 2011. a
Dahlgren, H., Ivchenko, N., and Lanchester, B. S.: Monoenergetic high-energy
electron precipitation in thin auroral filaments, Geophys. Res. Lett., 39,
L20101, https://doi.org/10.1029/2012GL053466, 2012. a
D'Angelo, N.: Type III spectra of the radar aurora, J. Geophys. Res., 78,
3987–3990, https://doi.org/10.1029/JA078i019p03987, 1973. a
EISCAT Scientific Association: Madrigal Database at EISCAT, available at: http://portal.eiscat.se/madrigal/, last access: 17 November 2021. a
Erdman, P. W. and Zipf, E. C.: Excitation of the OI
(3s5S0–3p5P; λ7774 Å) multiplet by electron impact on
O2, J. Chem. Phys., 87, 4540, https://doi.org/10.1063/1.453696, 1987. a
Fejer, B. G., Reed, R. W., Farley, D. T., Swartz, W. E., and Kelley, M. C.: Ion
cyclotron waves as a possible source of resonant auroral radar echoes, J.
Geophys. Res., 89, 187–194, https://doi.org/10.1029/JA089iA01p00187, 1984. a
Gallardo-Lacourt, B., Liang, J., Nishimura, Y., and Donovan, E.: On the Origin
of STEVE: Particle Precipitation or Ionospheric Skyglow?, Geophys. Res.
Lett., 45, 7968–7973, https://doi.org/10.1029/2018GL078509, 2018. a
Gillies, D. M., Donovan, E., Hampton, D., Liang, J., Connors, M., Nishimura,
Y., Gallardo-Lacourt, B., and Spanswick, E.: First Observations From the
TREx Spectrograph: The Optical Spectrum of STEVE and the Picket Fence
Phenomena, Geophys. Res. Lett., 46, 7207–7213, https://doi.org/10.1029/2019GL083272,
2019. a, b
Hedin, A. E.: Extension of the MSIS thermosphere model into the middle and
lower atmosphere, J. Geophys. Res., 96, 1159–1172, https://doi.org/10.1029/90JA02125,
1991. a, b
Itikawa, Y.: Cross sections for electron collisions with nitrogen molecules, J.
Phys. Chem. Ref. Data, 35, 31–53, https://doi.org/10.1063/1.1937426, 2005. a
Ivchenko, N., Blixt, E. M., and Lanchester, B. S.: Multispectral observations
of auroral rays and curls, Geophys. Res. Lett., 32, L18106,
https://doi.org/10.1029/2005GL022650, 2005. a
Julienne, P. S. and Davis, J.: Cascade and Radiation Trapping Effects on
Atmospheric Atomic Oxygen Emission Excited by Electron Impact, J. Geophys.
Res., 81, 1397–1403, https://doi.org/10.1029/JA081i007p01397, 1976. a
Kirkwood, S. and Nilsson, H.: High-latitude sporadic-E and other thin layers
– the role of magnetospheric electric fields, Space Sci. Rev., 91, 579–613,
https://doi.org/10.1023/A:1005241931650, 2000. a
Kwagala, N. K., Oksavik, K., Lorentzen, D. A., and Johnsen, M. G.: How Often Do
Thermally Excited 630.0 nm Emissions Occur in the Polar Ionosphere?, J.
Geophys. Res., 123, 698–710, https://doi.org/10.1002/2017JA024744, 2017. a
Lanchester, B. and Gustavsson, B.: Imaging of Aurora to Estimate the Energy and
Flux of Electron Precipitation, vol. 197 of Geophysical Monograph
Series, 171–182, American Geophysical Union (AGU),
https://doi.org/10.1029/2011GM001161, 2012. a
Lanchester, B. S., Kaila, K., and McCrea, I. W.: Relationship between large
horizontal electric fields and auroral arc elements, J. Geophys. Res., 101,
5075–5084, https://doi.org/10.1029/95JA02055, 1996. a, b
Lanchester, B. S., Rees, M. H., Lummerzheim, D., Otto, A.,
Sedgemore-Schulthess, K. J. F., Zhu, H., and McCrea, I. W.: Ohmic heating as
evidence for strong field-aligned currents in filamentary aurora, J. Geophys.
Res., 106, 1785–1794, https://doi.org/10.1029/1999JA000292, 2001. a, b
Lanchester, B. S., Ashrafi, M., and Ivchenko, N.: Simultaneous imaging of aurora on small scale in OI (777.4 nm) and N21P to estimate energy and flux of precipitation, Ann. Geophys., 27, 2881–2891, https://doi.org/10.5194/angeo-27-2881-2009, 2009. a, b, c
Litt, S. K., Smolyakov, A. I., Hassan, E., and Horton, W.: Ion thermal and
dispersion effects in Farley-Buneman instabilities, Phys. Plasmas,
22, 082112, https://doi.org/10.1063/1.4928387, 2015. a, b
Lummerzheim, D. and Lilensten, J.: Electron transport and energy degradation in the ionosphere: evaluation of the numerical solution, comparison with laboratory experiments and auroral observations, Ann. Geophys., 12, 1039–1051, https://doi.org/10.1007/s00585-994-1039-7, 1994. a
MacDonald, E. A., Donovan, E., Nishimura, Y., Case, N. A., Gillies, D. M.,
Gallardo-Lacourt, B., Archer, W. E., Spanswick, E. L., Bourassa, N., Connors,
M., Heavner, M., Jackel, B., Kosar, B., Knudsen, D. J., Ratzlaff, C., and
Schofield, I.: New science in plain sight: Citizen scientists lead to the
discovery of optical structure in the upper atmosphere, Sci. Adv., 4,
eaaq0030, https://doi.org/10.1126/sciadv.aaq0030, 2018. a
Marklund, G., Blomberg, L., Fälthammar, C.-G., and Lindqvist, P.-A.: On
intense diverging electric fields associated with black aurora, Geophys. Res.
Lett., 21, 1859–1862, https://doi.org/10.1029/94GL00194, 1994. a
Mende, S. B., Harding, B. J., and Turner, C.: Subauroral Green STEVE Arcs:
Evidence for Low-Energy Excitation, Geophys. Res. Lett., 46,
14256–14262, https://doi.org/10.1029/2019GL086145, 2019. a
Nygrén, T., Jalonen, L., Oksman, J., and Turunen, T.: The role of electric
field and neutral wind direction in the formation of sporadic E-layers, J.
Atmos. Terr. Phys., 46, 373–381, https://doi.org/10.1016/0021-9169(84)90122-3, 1984. a
Opgenoorth, H. J., Hägström, I., Williams, P. J. S., and Jones, G.
O. L.: Regions of strongly enhanced perpendicular electric fields adjacent to
auroral arcs, J. Atmos. Terr. Phys., 52, 449–458,
https://doi.org/10.1016/0021-9169(90)90044-N, 1990. a
Palmroth, M., Grandin, M., Helin, M., Koski, P., Oksanen, A., Glad, M. A.,
Valonen, R., Saari, K., Bruus, E., Norberg, J., Viljanen, A., Kauristie, K.,
and Verronen, P. T.: Citizen Scientists Discover a New Auroral Form: Dunes
Provide Insight Into the Upper Atmosphere, AGU Advances, 1,
e2019AV000133, https://doi.org/10.1029/2019AV000133, 2020. a
Price, D. J., Whiter, D. K., Chadney, J. M., and Lanchester, B. S.: High
resolution optical observations of neutral heating associated with the
electrodynamics of an auroral arc, J. Geophys. Res., 124, 9577–9591,
https://doi.org/10.1029/2019JA027345, 2019. a, b, c
Prikryl, P., Koehler, J. A., Sofko, G. J., McEwen, D. J., and Steele, D.:
Ionospheric ion cyclotron wave generation inferred from coordinated doppler
radar, optical, and magnetic observations, J. Geophys. Res., 92, 3315–3331,
https://doi.org/10.1029/JA092iA04p03315, 1987. a
Robinson, T. R. and Honary, F.: Adiabatic and isothermal ion-acoustic speeds of
stabilized Farley-Buneman waves in the auroral E-region, J. Atmos.
Terr. Phys., 55, 65–77, https://doi.org/10.1016/0021-9169(93)90155-R, 1993. a, b
Sahr, J. D., Farley, D. T., Swartz, W. E., and Providakes, J. F.: The altitude
of type 3 auroral irregularities: Radar interferometer observations and
implications, J. Geophys. Res., 96, 17805–17811,
https://doi.org/10.1029/91JA01544, 1991. a
Saito, S., Buchert, S. C., Nozawa, S., and Fujii, R.: Observation of isotropic electron temperature in the turbulent E region, Ann. Geophys., 19, 11–15, https://doi.org/10.5194/angeo-19-11-2001, 2001. a, b
Schlatter, N. M., Ivchenko, N., Sergienko, T., Gustavsson, B., and Brändström, B. U. E.: Enhanced EISCAT UHF backscatter during high-energy auroral electron precipitation, Ann. Geophys., 31, 1681–1687, https://doi.org/10.5194/angeo-31-1681-2013, 2013. a
Schunk, R. W. and Nagy, A. F.: Ionospheres, Atmospheric and Space Science
Series, Cambridge University Press, Cambridge, United Kingdom, 2000. a
Semeter, J., Hunnekuhl, M., MacDonald, E., Hirsch, M., Zeller, N., Chernenkoff,
A., and Wang, J.: The Mysterious Green Streaks Below STEVE, AGU Advances,
1, e2020AV000183, https://doi.org/10.1029/2020AV000183, 2020. a, b, c
Tuttle, S., Lanchester, B., Gustavsson, B., Whiter, D., Ivchenko, N., Fear, R., and Lester, M.: Horizontal electric fields from flow of auroral O+(2P) ions at sub-second temporal resolution, Ann. Geophys., 38, 845–859, https://doi.org/10.5194/angeo-38-845-2020, 2020. a, b
Whiter, D. K.: Dataset for Fine Scale Dynamics of Fragmented Aurora-Like
Emission, University of Southampton [data set], https://doi.org/10.5258/SOTON/D1928,
2021a. a
Whiter, D. K.: Auroral Structure and Kinetics (ASK) video observations
of Fragmented Aurora-like Emissions (FAEs), 2013/12/04 19:04 UT,
University of Southampton [data set], https://doi.org/10.5258/SOTON/D1930, 2021b. a
Whiter, D. K.: Auroral Structure and Kinetics (ASK) video observations
of Fragmented Aurora-like Emissions (FAEs), 2014/12/22 06:27 UT,
University of Southampton [data set], https://doi.org/10.5258/SOTON/D1929, 2021c. a
Whiter, D. K., Lanchester, B. S., Gustavsson, B., Ivchenko, N., and Dahlgren,
H.: Using multispectral optical observations to identify the acceleration
mechanism responsible for flickering aurora, J. Geophys. Res., 115, A12315,
https://doi.org/10.1029/2010JA015805, 2010.
a
Zhu, H., Otto, A., Lummerzheim, D., Rees, M. H., and Lanchester, B. S.:
Ionosphere-magnetosphere simulation of small-scale structure and dynamics, J.
Geophys. Res., 106, 1795–1806, https://doi.org/10.1029/1999JA000291, 2001. a
Short summary
This paper presents an analysis of high-resolution optical and radar observations of a phenomenon called fragmented aurora-like emissions (FAEs) observed close to aurora in the high Arctic. The observations suggest that FAEs are not caused by high-energy electrons or protons entering the atmosphere along Earth's magnetic field and are, therefore, not aurora. The speeds of the FAEs and their internal dynamics were measured and used to evaluate theories for how the FAEs are produced.
This paper presents an analysis of high-resolution optical and radar observations of a...
