Sustained Vertical Thermospheric Winds in the Auroral Zone

Bulk vertical motion in the thermosphere is of keen interest since it results in mass and thermal transport, disrupts local stratification and can change local composition, all of which can force complicated dynamics. In order to understand how the aurora might create vertical winds, we fielded a narrow-field Fabry-Perot interferometer in 2008, filtered for the 630.0 nm emission, at Poker Flat Research range. The instrument was run in a vertical observing mode with nine 90-second images followed by dark and laser calibration, producing a high time cadence record of vertical motion in thermosphere. During the spring of 2010 (when solar activity recovered to produce regular aurora displays) we found multiple examples of sustained vertical winds well correlated with the increase in 630.0 nm emission intensification due to auroral precipitation. The events last from 1 to >6 hours, with a typical duration of 4 hours, and typical speeds are 20 m/s, with some excursion to 60 m/s and greater. There is very little increase in the observed temperature during the same periods, typically less than 100 K, and in fact decreases of 50 K are often seen. We will describe the sustained vertical wind measurements in the context of several proposed mechanisms to produce vertical winds, especially in regard to ion-neutral coupling, and in conjunction with supporting measurements from PFISR, SuperDARN as well as other ground based instrumentation. In addition, we will compare the vertical wind measurements with simulation results from the Global Ionosphere Thermosphere Model.