Rayleigh-Taylor type instability in auroral patches

摘要

Based on observations by a high-resolution narrow field-of-view CCD camera, wefound small-scale (5-25 km) finger-like structures at the western boundary of auroralpatches in images obtained at Gillam (geomagnetic latitude: 65.5°N), Canada, in January2008. Since shear motion was not observed along the boundary of the patches, wesuggest that these structures are formed by macroscopic Rayleigh-Taylor type plasmainstability arising in the magnetospheric equatorial plane from the force balancing of the(eastward) magnetic tension force and the (westward) pressure gradient force.