Publication Date:
2015-08-25
Description:
Ion drag is known to play an important role in driving neutral thermosphere circulation at auroral latitudes, especially during the main phase of geomagnetic storms. During the recovery phase, the neutrals are known to drive the ions and generate ionospheric electric fields and currents via the disturbance dynamo mechanism. At mid-latitudes, the precise interplay between ions and neutrals is less understood largely because of the paucity of measurements that have been available. In this work, weinvestigate ion-neutral coupling at middle latitudes using co-located ion drift velocity measurements obtained from SuperDARN radars and neutral wind velocity and temperature measurements obtained from the NATION Fabry-Perot interferometers. We examine one recent storm period on October 2-3, 2013 during both the main phase and late recovery phase. By using ion-neutral momentum exchange theory and a time-lagged correlation analysis, we analyze the coupling timescales and dominant driving mechanisms. We observe that during the main phase the neutrals respond to the ion convection on a timescale of ∼ 84 minutes which is significantly faster than what would be expected from local ion-drag momentum forcing alone. This suggests other storm time influences are important for driving the neutrals during the main phase, such as Joule heating. During the late recovery phase, the neutrals are observed to drive the ion convection without any significant time delay, consistent with the so-called “neutral fly wheel effect" or disturbance dynamo persisting well into the late recovery phase.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
Permalink
