3:30 PM - 3:45 PM
[PEM28-09] Lower-thermospheric wind variations in auroral patches at the substorm recovery phase
Keywords:aurora, substorm, Fabry-Perot interferometer, ionosphere, thermosphere, polar region
Our researching activity is the first detailed investigation regarding the magnetosphere-ionosphere-thermosphere coupled system at the substorm recovery phase using comprehensive data sets of solar wind, geomagnetic field, auroral pattern, and FPI-derived wind. This study selected five events between November 2010 and January 2012, particularly focusing on the wind-variation signatures in the auroral morphology, and detected three clear evidences in all of the events: (1) wind fluctuations were isolated at the edge and/or in the darker area of the auroral patch, and the largest vertical amplitude and the longest oscillation period were about 20 m/s and about 10 minutes, respectively, (2) the convection electric field was smaller than 15 mV/m, and (3) wind fluctuations accompanied the pulsating aurora. These characteristics suggest that the energy dissipation to produce the wind fluctuations is localized in the auroral pattern. Joule heating and Lorentz force are not the principal mechanism because of small electric field. That is a notable characteristics different from the mechanism at the substorm growth and expansion phases. Particle heating must be a minor component in the energy dissipation because of the isolated wind fluctuation in the darker area. Some other mechanisms should play a principal role at the substorm recovery phase; but unknown yet.