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

Characteristics of vertical winds in the polar thermospheric region were ex amined using data sets generated with two types of Fabry-Perot interferomet ers at Poker Flat, Alaska (65.11 degreesN, 147.42 degreesW). The Communicat ions Research Laboratory Fabry-Perot Interferometer (CRLFPI) simultaneously observed the O I 557.7 nm and O I 630.0 nm emissions, whereas the Geophysi cal 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 emi ssions were 100-140 and 200-240 km, respectively. The data were obtained fr om October 1998 to February 1999, and our findings were as follows: (1) Obs ervations of the O I 630.0 nm emission showed that upward (downward) vertic al winds were often present when bright aurora existed equatorward (polewar d) of the observatory. This is consistent with previous studies [Crickmore et al., 1991; Innis et al., 1996, 1997]. (2) Comparison of vertical winds e stimated from two different wavelengths (557.7 and 630.0 nm) showed that ve rtical winds were often observed simultaneously at both wavelengths, as rep orted by Price ct al. [1995]. However, the vertical winds observed at diffe rent heights sometimes had different features when thin but bright aurora p assed over the observatory. A similar observation was reported by Ishii et al. [1999]. (3) Vertical winds were often observed along with divergence an d rotation of the horizontal wind field. Some vertical winds not associated with active aurora may be driven by the divergence in the horizontal wind.