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Ann. Geophys., 25, 1269-1278, 2007
www.ann-geophys.net/25/1269/2007/
© European Geosciences Union 2007
High time resolution measurements of the thermosphere from Fabry-Perot Interferometer measurements of atomic oxygen
E. A. K. Ford1,2, A. L. Aruliah1, E. M. Griffin1, and I. McWhirter1
1Atmospheric Physics Laboratory, Department of Physics and Astronomy, University College London, Gower Street, London, WC1E 6BT, UK
2British Antarctic Survey, High Cross, Madingley Road, Cambridge, CB3 0ET, UK
Abstract. Recent advances in the performance of CCD detectors have enabled a high time
resolution study of the high latitude upper thermosphere with Fabry-Perot
Interferometers (FPIs) to be performed. 10-s integration times were
used during a campaign in April 2004 on an FPI located in northern Sweden in
the auroral oval. The FPI is used to study the thermosphere by measuring the
oxygen red line emission at 630.0 nm, which emits at an altitude of
approximately 240 km. Previous time resolutions have been 4 min at best,
due to the cycle of look directions normally observed. By using 10 s
rather than 40 s integration times, and by limiting the number of full
cycles in a night, high resolution measurements down to 15 s were
achievable. This has allowed the maximum variability of the thermospheric
winds and temperatures, and 630.0 nm emission intensities, at approximately
240 km, to be determined as a few minutes. This is a significantly greater
variability than the often assumed value of 1 h or more. A Lomb-Scargle
analysis of this data has shown evidence of gravity wave activity with waves
with short periods. Gravity waves are an important feature of mesosphere-lower
thermosphere (MLT) dynamics, observed using many techniques and
providing an important mechanism for energy transfer between atmospheric
regions. At high latitudes gravity waves may be generated in-situ by
localised auroral activity. Short period waves were detected in all four
clear nights when this experiment was performed, in 630.0 nm intensities and
thermospheric winds and temperatures. Waves with many periodicities were
observed, from periods of several hours, down to 14 min. These waves
were seen in all parameters over several nights, implying that this
variability is a typical property of the thermosphere.
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