Poleward moving auroral arcs observed at the South Pole Station and the interpretation by field line resonances

摘要

We investigate the characteristics of poleward moving auroral arcs (PMAAs) observed with the all-sky monochromatic imager at the South Pole Station (74.3°CGLAT) in the interval 08:00-11:00 MLT on July 8, 2004. During this period, Pc 5 geomagnetic pulsations are also observed as well as quasi-stationary auroral patches (QSAPs), which keep their forms, luminosities, and locations for up to several hours. It is demonstrated that the PMAAs, Pc 5 pulsations in the north-south component, and oscillations in the drift of the QSAPs in the east-west direction have similar dominant periods and are well correlated with each other. The oscillatory ionospheric plasma drifts accompanying the PMAAs are extracted from the horizontal motion of the QSAPs and are found to propagate poleward with the PMAAs. The phase relations of the PMAAs and Pc 5 pulsations in the northward component with respect to the westward drift velocity of the QSAPs are close to anti-phase and in-phase, respectively. To examine whether these phenomena can be interpreted by field line resonances (FLRs), we perform a numerical simulation using a horizontally two-dimensional model that consists of the auroral acceleration region and the ionosphere with time-evolution conductivity. The results indicate that the observed data can be well explained by the FLR model with realistic physical parameters, except for the phase relation of the PMAAs with respect to the Pc 5 pulsations and the QSAPs.