Relationship between thermospheric vertical wind and the location of ionospheric current in the polar region

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We have been observing vertical winds in the polar thermosphere with a Fabry-Perot interferometer (FPI) installed at Poker Flat Research Range, Alaska. To introduce a new method to understand thermospheric wind system in the polar region, the vertical wind variations are compared with the peak location of ionospheric current deduced from magnetic field measurements on the ground in a case observed on December 5, 1999. The magnetometer data were obtained at Kaktovik, Fort Yukon, Poker Flat, and Gakona. The method of estimating ionospheric current was obtained from H. Luhr et al. (J. Atmos. Terr. Phys., 56, 81, 1994). The eastward current dominant interval was clearly separated from the westward current dominant one at 1130 UT (〜0030 MLT) in this case. The relation between the vertical wind and the location of the ionospheric current was clearly different before and after the boundary. Namely, the downward (upward) vertical wind was found to be dominant equatorward (poleward) of the ionospheric current after 1130 UT, which is consistent with results obtained in many previous works. However, this relation was found to be opposite before 1130 UT: the upward (downward) vertical wind was seen to be equatorward (poleward) of current.
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