HR: 17:30h
AN: SM54A-07    [Abstracts]
TI: Meso-scale and small-scale conjugacy of discrete and pulsating auroras observed with TV cameras
AU: * Sato, N
EM: nsato@nipr.ac.jp
AF: National Institute of Polar Research, 1-9-10, Kaga, Itabashi-ku, Tokyo, 173-8515 Japan
AU: Kadokura, A
EM: kadokura@nipr.ac.jp
AF: National Institute of Polar Research, 1-9-10, Kaga, Itabashi-ku, Tokyo, 173-8515 Japan
AU: Ebihara, Y
EM: ebihara@nipr.ac.jp
AF: National Institute of Polar Research, 1-9-10, Kaga, Itabashi-ku, Tokyo, 173-8515 Japan
AU: Saemundsson, T
EM: halo@raunvis.hi.is
AF: University of Iceland, Dunhaga 5, Reykjavik, IS-107 Iceland
AB: Syowa Station in Antarctica and Japanese stations in Iceland provide an ideal set of observatories to study geomagnetically conjugate optical auroras. A campaign of auroral conjugate observations using all-sky TV cameras has been carried out since 1984 during the equinox periods when simultaneous optical observations are possible under enough darkness in both hemispheres. In this paper we will focus on conjugacy studies of meso-scale and small-scale discrete and pulsating auroras. On 26 September 2003, a fine conjugate auroral substorm was observed at the conjugate-pair observatories Syowa and Tjornes. The observations covered the whole event, from the growth phase through the expansion phase to the recovery phase. Auroral breakup occurred at relatively low latitudes, after which the active auroral region expanded rapidly poleward. Subsequently, north-south structured auroral forms appeared from higher latitudes and extended to lower latitudes several times. During this event, meso-scale discrete auroras, including both east-west and north-south structured auroral forms, showed quite good conjugacy in shape, movement, and luminosity variations. This made it possible to trace the conjugate point with high time- and spatial resolution. On the other hand, small-scale discrete auroras gave no indication of conjugacy. For example, the rotation speed of vortices of curl-type aurora was higher in the southern hemisphere than in the northern hemisphere. Furthermore, pulsating auroras, which occurred during the recovery phase of the auroral substorm, showed good conjugacy in their meso-scale structure and shape, but the pulsation ON/OFF signature of the small-scale aurora appeared independent in the two hemispheres. This failure in conjugacy suggests that the generation region is not located in the equatorial region of the magnetosphere. We will discuss these meso-scale and small-scale auroral features in order to clarify how the IMF parameters and/or ionosphere-magnetosphere coupling processes control the conjugacy of the aurora.
DE: 2451 Particle acceleration
DE: 2704 Auroral phenomena (2407)
DE: 2736 Magnetosphere/ionosphere interactions
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting