Detachment of auroral arcs from the equatorward boundary of the auroral oval during substorm recovery phase

Abstract:

Formation of auroral arcs and their motion are manifestation of plasma dynamics in the magnetosphere. In this presentation, we show a common feature of auroral arc detachment from the equatorward boundary of the auroral oval, which occur mainly during substorm recovery phase. After the expansion onset of auroral substorms, the equatorward boundary of the auroral oval expands to lower latitudes. Around the beginning of the substorm recovery phase, the equatorward boundary of the oval start to retrieve back to higher latitudes. At this timing, equatorward detachments of weak auroral arcs are often seen in both 630.0-nm and 557.7-nm images and north-south keograms at subauroral latitudes. The detached arc can later become Stable Auroral Red (SAR) arcs [e.g., Shiokawa et al., AIP, 2009; EPS, 2017; Takagi et al., GRL, 2018] and/or STEVE [e.g., Gallardo-Lacourt et al., JGR, 2018]. We will discuss possible mechanisms that can create this auroral arc detachment from the auroral oval in the context of magnetospheric plasma processes.

Gallardo-Lacourt et al. (JGR, 2018) https://doi.org/10.1029/2018JA025368

Shiokawa et al. (AIP Conf. Proc., 2009) https://doi.org/10.1063/1.3169292

Shiokawa et al. (EPS, 2017) https://doi.org/10.1186/s40623-017-0745-9

Takagi et al. (GRL, 2018) https://doi.org/10.1029/2018GL079615