Airglow Patches in the Polar Cap Region: A Review
Polar cap airglow patches have been known as regions of enhanced 630.0 nm airglow detected by ground-based all-sky imagers at the polar cap latitudes well inside the main auroral oval. Although they were already recognized almost four decades ago as counterparts of polar cap (plasma density) patches, such airglow observations had not been utilized extensively for the studies of ionospheric structures and/or magnetosphere-ionosphere coupling processes in the polar cap. In the last two decades, following the development of highly-sensitive airglow imagers equipped with cooled CCD (Charge Coupled Device) cameras, it has become possible to visualize the dynamical temporal evolution and complicated spatial structure of airglow patches with improved signal-to-noise ratio. Such a progress has enabled us not only to use airglow patches as tracers for plasma convection in the polar cap but also to understand the generation of small-scale plasma irregularities in the ionospheric F region. In addition, recent observations demonstrated a case in which an airglow patch was accompanied by an intense flow channel and corresponding field-aligned current structure along its edges. This implies that airglow patches can signify magnetosphere-ionosphere coupling process in the region of open field lines at the polar cap latitudes, serving as a remote sensing tool just like auroras do. Further studies showed an association of airglow patches with the intensification of aurora on the nightside (Poleward Boundary Intensification: PBI and/or streamer) leading to the expansion phase onset of substorms. This paper reviews such recent progresses in the researches of airglow patches obtained by combining data from all-sky airglow imagers, radars and low-altitude satellite observations in the polar cap.
KeywordsAirglow Polar cap Ionospheric convection Substorm Field-aligned currents
K.H. is supported by JSPS Kakenhi (26302006). Y.Z. is supported by UCAR’s Cooperative Programs for the Advancement of Earth System Science (Jack Eddy Postdoctoral Fellowship), and by National Science Foundation (AGS-1664885). Y.N. is supported by NASA grant NNX17AL22G and 80NSSC18K0657, NSF grants PLR-1341359, AGS-1737823, and AFOSR FA9559-16-1-0364.
- H.C. Carlson, A voyage of discovery into the polar cap and Svalbard, in Proceedings of the Egeland Symposium on Auroral and Atmospheric Research, Dep. of Phys., Univ. of Oslo, Norway, ed. by J. Moen, J.A. Holtet (2003), pp. 33–54. ISBN 82-91853-09-6 Google Scholar
- G. Crowley, Critical review of ionospheric patches and blobs, in The Review of Radio Science 1992–1996, ed. by W. Ross Stone (Oxford University Press, Oxford, 1996) Google Scholar
- H. Dahlgren, J.L. Semeter, K. Hosokawa, M.J. Nicolls, T.W. Butler, M.G. Johnsen, K. Shiokawa, C. Heinselman, Direct three-dimensional imaging of polar ionospheric structures with the Resolute Bay Incoherent Scatter Radar. Geophys. Res. Lett. 39, L05104 (2012a). https://doi.org/10.1029/2012GL050895 ADSCrossRefGoogle Scholar
- H. Dahlgren, G.W. Perry, J.L. Semeter, J.-P. St-Maurice, K. Hosokawa, M.J. Nicolls, M. Greffen, K. Shiokawa, C. Heinselman, Space-time variability of polar cap patches: direct evidence for internal plasma structuring. J. Geophys. Res. 117, A09312 (2012b). https://doi.org/10.1029/2012JA017961 ADSCrossRefGoogle Scholar
- L.V. Goodwin, B. Iserhienrhien, D.M. Miles, S. Patra, C. van der Meeren, S.C. Buchert, J.K. Burchill, L.B.N. Clausen, D.J. Knudsen, K.A. McWilliams, J. Moen, Swarm in situ observations of F region polar cap patches created by cusp precipitation. Geophys. Res. Lett. 42, 996–1003 (2015). https://doi.org/10.1002/2014GL062610 ADSCrossRefGoogle Scholar
- K. Hosokawa, K. Shiokawa, Y. Otsuka, T. Ogawa, J.-P. St-Maurice, G.J. Sofko, D.A. Andre, Relationship between polar cap patches and field-aligned irregularities as observed with an all-sky airglow imager at Resolute Bay and the PolarDARN radar at Rankin Inlet. J. Geophys. Res. 114, A03306 (2009a). https://doi.org/10.1029/2008JA013707 ADSCrossRefGoogle Scholar
- L.R. Lyons, Y. Nishimura, H.-J. Kim, E. Donovan, V. Angelopoulos, G. Sofko, M. Nicolls, C. Heinselman, J.M. Ruohoniemi, N. Nishitani, Possible connection of polar cap flows to pre- and post-substorm onset PBIs and streamers. J. Geophys. Res. 116, A12225 (2011). https://doi.org/10.1029/2011JA016850 ADSCrossRefGoogle Scholar
- Y. Nishimura, Y. Zou, Studying the Auroras and What Makes Them Shine (Scientia, Bristol, 2017) Google Scholar
- T. Sato, Morphology of ionospheric F2 disturbances in the polar regions. Rep. Ionos. Space Res. Jpn. 131, 91 (1959) Google Scholar
- C. Van der Meeren, K. Oksavik, D.A. Lorentzen, M.T. Rietveld, L.B.N. Clausen, Severe and localized GNSS scintillation at the poleward edge of the nightside auroral oval during intense substorm aurora. J. Geophys. Res. Space Phys. 120, 10,607–10,621 (2015). https://doi.org/10.1002/2015JA021819 CrossRefGoogle Scholar
- B. Wang, Y. Nishimura, L.R. Lyons, Y. Zou, H.C. Carlson, H.U. Frey, S.B. Mende, Analysis of close conjunctions between dayside polar cap airglow patches and flow channels by all-sky imager and DMSP. Earth Planets Space 68(1), 150 (2016). https://doi.org/10.1186/s40623-016-0524-z ADSCrossRefGoogle Scholar
- Y. Zou, Y. Nishimura, L.R. Lyons, K. Shiokawa, E.F. Donovan, J.M. Ruohoniemi, K.A. McWilliams, N. Nishitani, Localized polar cap flow enhancement tracing using airglow patches: statistical properties, IMF dependence, and contribution to polar cap convection. J. Geophys. Res. Space Phys. 120, 4064–4078 (2015). https://doi.org/10.1002/2014JA020946 ADSCrossRefGoogle Scholar