Scale size‐dependent characteristics of the nightside aurora. Issue 2 (17th February 2017)

• Record Type: Journal Article
• Authors: Humberset, B. K.; Gjerloev, J. W.; Samara, M.; Michell, R. G.
• Is Part Of: Journal of geophysical research. Volume 122:Issue 2(2017)
• Page Start: 2455
• Page End: 2466
• Publication Date: 2017-02-17
• Subjects: auroral characteristics -- spatiotemporal -- multipoint -- magnetosphere‐ionosphere coupling -- aurora -- scale size; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1002/2016JA023695
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: We have determined the spatiotemporal characteristics of the magnetosphere‐ionosphere (M‐I) coupling using auroral imaging. Observations at fixed positions for an extended period of time are provided by a ground‐based all‐sky imager measuring the 557.7 nm auroral emissions. We report on a single event of nightside aurora (∼22 magnetic local time) preceding a substorm onset. To determine the spatiotemporal characteristics, we perform an innovative analysis of an all‐sky imager movie (19 min duration, images at 3.31 Hz) that combines a two‐dimensional spatial fast Fourier transform with a temporal correlation. We find a scale size‐dependent variability where the largest scale sizes are stable on timescales of minutes while the small scale sizes are more variable. When comparing two smaller time intervals of different types of auroral displays, we find a variation in their characteristics. The characteristics averaged over the event are in remarkable agreement with the spatiotemporal characteristics of the nightside field‐aligned currents during moderately disturbed times. Thus, two different electrodynamical parameters of the M‐I coupling show similar behavior. This gives independent support to the claim of a system behavior that uses repeatable solutions to transfer energy and momentum from the magnetosphere to the ionosphere. Key Points: An innovative 2‐D analysis of all‐sky images revealing the characteristics of the magnetosphere‐ionosphere coupling The largest auroral scale sizes are stable on timescales of minutes while the small scale sizes are more variable The characteristics of the nightside aurora and field‐aligned currents are in remarkable agreement