Solar cycle variations of the thermospheric meridional wind over Japan derived from measurements of hmF(2)

This paper describes an analysis of the meridional equivalent neutral wind for geomagnetically quiet conditions as determined from data collected at t he Kokubunji ionosonde station (35.7N, 139.5B), Japan over one solar cycle (1981-1991). The wind is derived from the altitude of peak F-2 layer electr on density using the Field Line Interhemispheric Plasma (FLIP) model. For l ow and moderate solar activity the wind is poleward in the daytime and equa torward in the nighttime. For high solar activity the wind is weak and almo st always poleward throughout the day. In winter the local time of peak pol eward velocity occurs in the afternoon for low solar activity but in the ni ght for high solar activity. In summer the peak poleward wind occurs in the morning for all levels of solar activity. The diurnal amplitude decreases with increasing solar activity. It also reaches its maximum around the sols tices and its minimum around the equinoxes. The mean wind is larger at sola r maximum than solar minimum, except for the year 1984. The daily-mean wind is smallest in summer and largest in winter. Qualitatively, the meridional wind at Asian midlatitudes has characteristics similar to those seen in ot her sectors (such as Millstone Hill, Boulder, Wallops Island, King George I sland, and Saint-Santin), but the details in behavior are different and war rant further investigation.