Northeastward motion of nighttime medium-scale traveling ionospheric disturbances at middle latitudes observed by an airglow imager

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Nighttime medium-scale traveling ionospheric disturbances (MSTIDs) observed
in 630-nm airglow images at middle latitudes are known to have a predominantly
northwest-southeast phase surface and to move southwestward in the Northern
Hemisphere of Earth. However, the mechanisms of MSTID generation and their
systematic southwestward motion have not been clarified. In this paper, we report the
‘‘northeastward’’ motion of the MSTIDs observed at Paratunka, Far East Russia (52.97°N,
158.25°E), using an all-sky 630-nm airglow imager at 2000–2300 LT on 19 August 2007.
The MSTIDs moved first southwestward but then back northeastward in the northern
part of the images. The northeastward motion of the MSTIDs took place coincident with a
F layer height decrease observed by an ionosonde at Paratunka. The F layer height
decrease was also confirmed by an enhancement of the 630-nm airglow intensity, which
seemed to propagate from northeast to southwest. This fact suggests that the F layer
height decrease was caused by poleward wind enhancement rather than westward electric
field. These observations imply that the F layer height decrease or the poleward
thermospheric wind has some role in the northeastward turning of the MSTID propagation
direction.

Shiokawa K., Otsuka Y., Nishitani N., Ogawa T., Tsugawa T., Maruyama T., Smirnov S.E., Bychkov V.V., Shevtsov B.M. Northearstward motion of nighttime medium-scale traveling ionosferic disturbances at middle latitudes observed by an airglow imager // Journal of Geophysical Research. 2008. T. 113. № 12.