Observations Of Small-scale Thermospheric Neutral Winds Associated With Auroral Activity

Details Observations Of Small-scale Thermospheric Neutral Winds Associated With Auroral Activity Observations Of Small-scale Thermospheric Neutral Winds Associated With Auroral Activity

Dec 2003

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003agufmsa22a0099s&link_type=abstract

American Geophysical Union, Fall Meeting 2003, abstract #SA22A-0099

Computer Science

Sound

0358 Thermosphere: Energy Deposition, 2407 Auroral Ionosphere (2704), 2427 Ionosphere/Atmosphere Interactions (0335), 2704 Auroral Phenomena (2407), 3369 Thermospheric Dynamics (0358)

Scientific paper

Many researchers reported that strong thermospheric vertical winds (10-150 m/s) would occur associated with auroral activity. However, the generation processes of vertical winds and its relationship to atmospheric gravity waves (AGWs) are not understood well. To clarify the characteristics of neutral winds associated with auroral emission, we have examined vertical and horizontal winds estimated from OI 557.7 nm and OI 630 nm data obtained by a Fabry-Perot Doppler at Syowa station, Antarctica (66.4 deg. MLAT). In this paper, we present case studies of vertical winds obtained on 20 nights during the period from July to October in 1996, and in addition, the quasi-periodic oscillation of neutral winds observed on September 12, 1996. The characteristics of vertical winds are summarized as follows. 1) In 5 cases out of 8 breakup events, strong ( ˜20 m/s) and temporal upward winds existed in the E region poleward of breakup aurora. 2) Downward winds ( ˜ - 40 m/s) were generally seen in the E region within bright auroras. 3) Oscillations of vertical winds with a period of a few hours were observed in the F region on 4 cases when the aurora oval appeared in the poleward region of Syowa. On the case on September 12, 1996, it is found from 557.7 nm data that quasi-periodic wind oscillations occurred poleward of Syowa, while a stable discrete aurora appeared in the ˜350 km equatorward of Syowa. The amplitudes of neutral wind variations were considerably large ( ˜600 m/s), and the typical period was ˜8 minutes which is almost equal to the local Brunt-Visala period estimated from the MSISE-90 model. It is concluded that we could not attribute these periodic winds to AGWs since the apparent phase velocity was ˜930 m/s which is much greater than the local sound speed ( ˜410 m/s), and, therefore, it is difficult to apply a simple dispersion relation of AGWs to the observed wind variations.

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