Assimilated observations of thermospheric winds, the aurora, and ionospheric currents over Alaska

Abstract

We present simultaneous measurements of thermospheric winds, auroral emissions, and ionospheric currents over Alaska, obtained from four separate instruments. Thermospheric (F region) wind maps were recorded by an all‐sky imaging Fabry‐Perot spectrometer located at Poker Flat and observing at λ630.0 nm. Auroral images at λ557.7 nm were obtained from the low‐resolution visible imager on board the Polar satellite. White‐light all‐sky auroral images were recorded by ground‐based all‐sky cameras located in Alaska at Poker Flat (65° 07′N, 212° 34′E) and at Kaktovik (70° 06′N, 217° 24′E). Finally, the east‐west component of the ionospheric F region plasma convection was inferred using the Alaskan meridian chain of magnetometers. Montage images of these four data sets are presented, projected onto a geographic map of the Alaskan region. We examine a 10‐hour period during the Alaskan local nighttime of February 10, 1997. These montages illustrate a close relationship between spatial structures occurring in the aurora, in the ionospheric plasma convection, and in the F region wind field. Latitudinal shear of the geomagnetic zonal wind, often observed in the premidnight time sector, was seen to be associated with both the equatorward and poleward boundaries of the discrete aurora. We focus particularly on a period commencing just after 0900 UT, when a strong shear in the zonal wind was observed to sweep southward across Alaska. After magnetic midnight the wind field was dominated by the emergence of the “cross‐polar jet” from the polar cap. This overwhelmed any wind features associated with local auroral processes.