Comparative study of large‐scale auroral signatures of substorms, steady magnetospheric convection events, and sawtooth events. Issue 6 (27th June 2017)

• Record Type: Journal Article
• Authors: Walach, M.‐T.; Milan, S. E.; Murphy, K. R.; Carter, J. A.; Hubert, B. A.; Grocott, A.
• Is Part Of: Journal of geophysical research. Volume 122:Issue 6(2017)
• Page Start: 6357
• Page End: 6373
• Publication Date: 2017-06-27
• Subjects: magnetospheric modes -- aurora -- solar wind‐magnetospheric coupling -- substorms -- steady magnetospheric convection events -- sawtooth events; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1002/2017JA023991
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: This paper investigates the auroral evolution during different magnetospheric modes: substorms, steady magnetospheric convection, and sawtooth events. We undertake a superposed epoch analysis using data from the Imager for Magnetopause‐to‐Aurora Global Exploration Far Ultraviolet spectrographic imager and wideband imaging camera for each of these event types. We find that the auroral oval narrows and shows an equatorward movement prior to substorm onset. At substorm onset, the auroral oval brightens explosively near 23 magnetic local time (MLT). After this the aurorae expand poleward and the brightening stretches duskward and dawnward, with the duskward expansion being faster. Approximately 20 min after substorm onset, the aurorae begin to dim. Steady magnetospheric convection events with preceding substorms initially show the same signatures as substorms, but instead of the recovery after 20 min postonset, the aurorae stay bright for an extended period of time (at least 4 h after onset). Despite continued dayside driving of the system during steady magnetospheric convection events, we see a reconfiguration in the nightside auroral activity, taking place between 120 to 150 min after onset. Sawtooth events show very similar signatures to substorms, except for the auroral emission being much brighter, covering a wider MLT extent, and taking significantly less time to recover. The proton aurorae during substorms take ∼2–4 h to dim, during sawtooth events this process takes less than 1 h, despite enhanced reconnection rates. A similar effect is seen in the electron aurorae, albeit not as extreme. Key Points: We compare average nightside aurora of different magnetospheric modes (substorms, steady magnetospheric convection events, and sawtooth events) Steady magnetospheric convection events produce brighter aurora than substorms, but sawtooth events are the brightest overall Despite much higher magnetospheric driving of sawtooth events, the aurora takes half the time to dim than after substorms