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Polar vortex evolution during Northern Hemispheric winter 2004/05
(Journal article; Tidsskriftartikkel; Peer reviewed, 2007)
The 16-day planetary waves: multi-MF radar observations from the arctic to equator and comparisons with the HRDI measurements and the GSWM modelling results
(Journal article; Peer reviewed; Tidsskriftartikkel, 2002)
The mesospheric and lower thermospheric (MLT) winds (60–100 km) obtained by multiple MF radars, located from the arctic to equator at Tromsø (70° N, 19° E), Saskatoon (52° N, 107° W), London (43° N, 81° W), Hawaii (21° N, ...
On the possibility of ion-drag to induce dynamic instability in the lower thermosphere neutral gas
(Journal article; Peer reviewed; Tidsskriftartikkel, 2000)
Strong wind shears may result in dynamic instability, often characterised by the Richardson number lying between zero and 0.25. The extent to which electric-field driven ion flow may induce such neutral wind shears is ...
Periodicities in energy dissipation rates in the auroral mesosphere/lower thermosphere
(Journal article; Peer reviewed; Tidsskriftartikkel, 2003)
It is possible for medium-frequency (MF) radar systems to estimate kinetic energy dissipation rates by measuring signal fading times. Here, we present approximately 5 years of such results from Tromsø (69° N, 19° E) and ...
An analogy to the Reynolds number for the neutral gas component of a weak plasma
(Journal article; Peer reviewed; Tidsskriftartikkel, 2001)
The Reynolds number Re is used as a metric to assess whether or not a flow may contain turbulence. In a weakly ionised gas with an external electric field imposed, ions exert a drag on the neutral particles. Thus, a component ...
Testing the hypothesis of the influence of neutral turbulence on the deduction of ambipolar diffusivities from meteor trail expansion
(Journal article; Peer reviewed; Tidsskriftartikkel, 2005-03-30)
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 ...
Spectral characteristics of high latitude raw 40MHz cosmic noise signals
(Journal article; Tidsskriftartikkel; Peer reviewed, 2015-07-07)
Cosmic noise at 40 MHz is measured at Ny-Ålesund (79◦ N, 12◦ E) using a relative ionospheric opacity meter (“riometer”). A riometer is normally used to determine the degree to which cosmic noise is absorbed by the ...
Isolated lower mesospheric echoes seen by medium frequency radar at 70º N, 19º E
(Journal article; Peer reviewed; Tidsskriftartikkel, 2006-11-23)
We have noted sporadic instances of strong isolated reflections of medium frequency (MF) radar waves from the mesosphere from as low as 50 km altitude and have devised a set of criteria for isolating these apparently ...
Altitude calibration of the Tromsø medium frequency radar
(Research report; Forskningsrapport, 2004)
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 ...
Climatic trends in E-region critical frequency and virtual height above Tromsø (70 degrees N, 10 degrees E)
(Journal article; Tidsskriftartikkel; Peer reviewed, 2007-11-29)
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 ...