Vertical wind observations with two Fabry‐Perot interferometers at Poker Flat, Alaska

Abstract

Characteristics of vertical winds in the polar thermospheric region were examined using data sets generated with two types of Fabry‐Perot interferometers at Poker Flat, Alaska (65.11°N, 147.42°W). The Communications Research Laboratory Fabry‐Perot Interferometer (CRLFPI) simultaneously observed the O I 557.7 nm and O I 630.0 nm emissions, whereas the Geophysical Institute Scanning Doppler‐Imaging Interferometer (GI‐SDI) observed the O I 630.0 nm emission. The height of the O I 557.7 nm and O I 630.0 nm emissions were 100–140 and 200–240 km, respectively. The data were obtained from October 1998 to February 1999, and our findings were as follows: (1) Observations of the O I 630.0 nm emission showed that upward (downward) vertical winds were often present when bright aurora existed equatorward (poleward) of the observatory. This is consistent with previous studies [Crickmore et al., 1991; Innis et al., 1996, 1997]. (2) Comparison of vertical winds estimated from two different wavelengths (557.7 and 630.0 nm) showed that vertical winds were often observed simultaneously at both wavelengths, as reported by Price et al. [1995]. However, the vertical winds observed at different heights sometimes had different features when thin but bright aurora passed over the observatory. A similar observation was reported by Ishii et al. [1999]. (3) Vertical winds were often observed along with divergence and rotation of the horizontal wind field. Some vertical winds not associated with active aurora may be driven by the divergence in the horizontal wind.