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14 1. INTRODUCTION
lines at altitudes of about 130 and 240 km, respectively. Significant upwelling events were
measured on the poleward side of the auroral oval during geomagnetically active conditions,
and a schematic model was used to describe an event from which the horizontal scale of the
upwelling region is estimated to be less than 320 km in the lower thermosphere and less than
800 km in the upper thermosphere.
1.5 Purpose of this thesis
In order to investigate the Earth's thermosphere in which a variety of dynamical and
chemical processes take place in response to the variations of energy input, we have made an
overall improvement of the prototype Fabry-Perot Doppler imaging system (FPDIS) which
had been developed by the Tohoku University optical group in 1989 [Nakajima et al., 1995].
The FPDIS measures the Doppler shifts and widths of aurora and/or airglow emission lines
of 01557.7 nm and 01630.0 nm over a wide field of. view (165°) to obtain two-dimensional
distributions of winds and temperatures in the E- and F-region.
We installed the improved FPDIS at Syowa station (69.00°S, 39.58°E, 66° INV, L —6.1)
in February 1994, and carried out observations of thermospheric neutral winds for 57 nights
covering various auroral conditions in the austral winter period from March to September
in 1994. Since Syowa station is located just in the auroral zone, the site is quite suitable to
observe the variations of thermospheric winds directly associated with auroral disturbances.
Syowa station has also enough facilities to observe auroral, magnetic and ionospheric dis-
turbances; an SIT all-sky camera for auroral observations, fiuxgate and search coil mag-
netometer for geomagnetic field observations, an ionosonde and a multi-beam riometer for
ionosphere observations. Further, Syowa station has a satellite tracking and data acquisi-
tion system which acquires in-situ measurement data from the Akebono (EXOS-D) satellite
passing above the site.
The main purpose of this study is to understand the response of thermospheric neu-
tral winds in the high-latitude E- and F-region to auroral disturbances by the Fabry-Perot
Doppler imaging observations characterized by high temporal and spatial resolution in the
thermospheric wind measurement. The maximum time resolution of the FPDIS measure-
ment is I min for the 01557.7 nm emission and 3 min for the 01630.0 nm emission, while
its typical spatial resolution is about 50 km for the 01557.7 nm emission and about 100
km for the 01630.0 nm emission. Several characteristic variations of the therrnospheric neu-
tral winds associated with auroral disturbances are examined in detail. The principle and