In situ observations of instabilities in the mesopause region using foil chaff technique during the Waves in Airglow Structures Experiment (WAVE) campaigns

In order to investigate the dynamics of the mesopause region, foil chaff experiments were carried out successfully during the WAVE2000 and WAVE2004 campaigns at Kagoshima, Japan. In the WAVE2004 campaign, the height profiles of the horizontal and vertical wind speeds were obtained. The wind shear layers of >40 m/s/km were located around the altitudes of 89 and 95 km, and the profile of the Richardson number reveals the existence of dynamically unstable layers at about the same height region. Ripple observations using the all-sky imagers also support the possibility of dynamical instabilities. In the WAVE2000 campaign, a prominent small-scale feature around an altitude of 90.5 km appeared in both the horizontal and vertical chaff motions. These results demonstrate that the foil chaff technique is a valuable tool for in situ observation of small-scale turbulence features around the mesopause.