An unusual mesospheric bore event observed at high latitudes over Antarctica

Abstract

All‐sky CCD observations of short‐period mesospheric gravity waves have been made from Halley Station, Antarctica (76°S, 27°W). On 27 May, 2001, an unusual wave event exhibiting several features characteristic of a “bore” was observed in the OH, Na, and O2 nightglow emissions. Mesospheric bores are rare wave events that have previously been observed at mid‐ and low‐latitudes. This event was particular interesting as: (1) it initially appeared as a single, high contrast, linear front, accompanied by a sharp enhancement in intensity in all three emissions, (2) a number of trailing wave crests were observed to form with a measured growth rate of 6.6 waves/hr, and (3) the wave pattern exhibited unusual dynamics with significant variability in the observed phase speed and a reduction in the horizontal wavelength by ∼50% over a 1‐hr period. The location of Halley and the observed propagation suggests a ducted wave consistent with current bore models.