http://hdl.handle.net/10037/568 2012-02-12T06:30:02Z http://hdl.handle.net/10037/3559 Hall, Chris; Manson, Alan; Meek, Chris; Nozawa, Satonori<br /> 2006-12-31T23:00:00Z Hall, Chris Manson, Alan Meek, Chris Nozawa, Satonori http://hdl.handle.net/10037/3298 Hall, Chris; Xu, X; Manson, A. H.; Meek, Chris; Chshyolkova, Tatyana; Drummond, J. R.; Riggin, D.; Hibbins, RE<br /> 2008-12-31T23:00:00Z Hall, Chris Xu, X Manson, A. H. Meek, Chris Chshyolkova, Tatyana Drummond, J. R. Riggin, D. Hibbins, RE http://hdl.handle.net/10037/3297 Hall, Chris; Chshyolkova, Tatyana; Manson, Alan; Meek, Chris; Aso, Takehiko; Avery, S. K.; Hocking, W. K.; Igarashi, K.; Jacobi, C.; Makarov, N.; Mitchell, Nick; Murayama, Y.; Singer, Werner; Thorsen, D.; Tsutsumi, Masaki<br /> 2006-12-31T23:00:00Z Hall, Chris Chshyolkova, Tatyana Manson, Alan Meek, Chris Aso, Takehiko Avery, S. K. Hocking, W. K. Igarashi, K. Jacobi, C. Makarov, N. Mitchell, Nick Murayama, Y. Singer, Werner Thorsen, D. Tsutsumi, Masaki http://hdl.handle.net/10037/3295 Hall, Chris; Xu, X; Manson, Alan; Meek, Chris; Chshyolkova, Tatyana; Drummond, J. R.; Jacobi, Ch.; Riggin, D.; Hibbins, R.E.; Tsutsumi, Masaki; Hocking, W. K.; Ward, W.<br /> 2008-12-31T23:00:00Z Hall, Chris Xu, X Manson, Alan Meek, Chris Chshyolkova, Tatyana Drummond, J. R. Jacobi, Ch. Riggin, D. Hibbins, R.E. Tsutsumi, Masaki Hocking, W. K. Ward, W. http://hdl.handle.net/10037/3294 Hall, Chris; Manson, Alan; Meek, Chris; Chshyolkova, Tatyana; Xu, X.; Aso, Takehiko; Drummond, J. R.; Hocking, Wayne; Jacobi, Ch.; Tsutsumi, Masaki; Ward, W.<br /> 2008-12-31T23:00:00Z Hall, Chris Manson, Alan Meek, Chris Chshyolkova, Tatyana Xu, X. Aso, Takehiko Drummond, J. R. Hocking, Wayne Jacobi, Ch. Tsutsumi, Masaki Ward, W. http://hdl.handle.net/10037/2411 Hall, Chris; Husøy, Bjørn Ove<br /> Although the Tromsø Medium Frequency Radar situated at Ramfjordmoen, Norway (69°N, 19°E) has been operating for over a quarter of a century, no definitive altitude calibration has ever been documented using independent measurements of the same atmosphere. Here we perform calibrations using the recently installed (November 2003) Nippon/Norway Tromsø Meteor Radar by identifying wind features in the same volume. We also perform an independent check using oscilloscope measurements supplemented by an acoustic delay line.<br /> This publication is the inaugural report in the series Tromsø Geophysical Observatory Reports.<br /> 2003-12-31T23:00:00Z Hall, Chris Husøy, Bjørn Ove http://hdl.handle.net/10037/2392 Aspaas, Per Pippin; Hansen, Truls Lynne<br /> In the years 1768-1770 an expedition lead by the Austrian/Hungarian astronomer and Jesuit Father Maximilian Hell travelled to Vardø in the northernmost part of Norway. The main objective of the expedition was to observe the transit of Venus in June 1769. However, scientific investigations in several other fields were also performed, among them observations of the magnetic declination. From the original Latin manuscripts a two months series of declinations in Vardø as well as a number of observations carried out on the return voyage from Vardø, have been extracted. Methods of observations are described. The manuscripts on which the work is based are reproduced in the report.<br /> 2004-12-31T23:00:00Z Aspaas, Per Pippin Hansen, Truls Lynne http://hdl.handle.net/10037/2385 Cannon, P. S.; Hall, Chris; Brekke, Asgeir<br /> We have examined the long time series of observations of E-region virtual height (1948–2006) and critical frequency (1935-2006) hitherto made by the Tromsø ionosonde at 70 degrees N, 19 degrees E. Combining a simplistic trend analysis with a rigorous treatment of errors we identify a negative trend in critical frequency. While a similar analysis of the virtual height h'E also suggests a negative trend, a closer examination reveals a possible weak positive trend prior to ~1975 and a strong negative trend from ~1975 to present. These two metrics of essentially the same feature of the ionosphere do not exhibit the same signature since critical frequency is controlled by photochemistry within the E-layer while height is controlled by pressure level. We further find that the trend in critical frequency is a daylight/summer phenomenon, no significant trend being evident in the winter subset of the data. On the other hand, the trends in virtual height are independent of season/daylight.<br /> This is the publishers version/PDF (published in Annales Geophysicae, an open access journal of the European Geosciences Union)<br /> 2007-11-28T23:00:00Z Cannon, P. S. Hall, Chris Brekke, Asgeir http://hdl.handle.net/10037/579 Nozawa, S.; Hall, Chris; Manson, A.H.; Meek, C.E.<br /> We search for the presence of tidal signatures in high latitude mesospheric turbulence as parameterized by turbulent energy dissipation rate estimated using a medium frequency radar, quantifying our findings with the aid of correlation analyses. A diurnal periodicity is not particularly evident during the winter and spring months but is a striking feature of the summer mesopause. While semidiurnal variation is present to some degree all year round, it is particularly pronounced in winter. We find that the maximum in the summer 24-h variation corresponds to that of the westward phase of the diurnal tide, and that the maximum in the winter 12 h variation corresponds to that of the southward phase of the semidiurnal tide. This information is used to infer the horizontal propagation direction of gravity waves: during the summer the eastward direction is consistent with closure of the summer vortex, while in winter the inferred directions require more complex arguments.<br /> 2005-12-31T23:00:00Z Nozawa, S. Hall, Chris Manson, A.H. Meek, C.E. http://hdl.handle.net/10037/578 Aso, T.; Hall, Chris; Tsutsumi, M.; Nozawa, S.; Manson, A.H.; Meek, C.E.<br /> Fading times of radar echoes from underdense meteor trails in the upper mesosphere/lower thermosphere are commonly used to determine ambipolar diffusivities and hence ambient temperature. Diffusivities are generally expected to increase exponentially with height through the region from which the meteor trail echoes are obtained, viz., typically 70-110km altitude for a ~30-MHz radar. In practice, however, this is more the exception: unexpectedly large diffusivities are obtained in the lower part of the regime, and unexpectedly low values are obtained in the upper part; only in the few kilometres on either side of the maximum in echo occurrence (viz., 90km for a 30-MHz radar) does the diffusivity profile behave as expected. Hall (2002) hypothesised that neutral turbulence might be enhancing expansion of the meteor trail in the lower part of the regime. In this communication, due to results only available since the publication of Hall's suggestion, we are able to refute the hypothesis.<br /> 2005-03-29T22:00:00Z Aso, T. Hall, Chris Tsutsumi, M. Nozawa, S. Manson, A.H. Meek, C.E.