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| Titel |
TID characterised using joint effort of incoherent scatter radar and GPS |
| VerfasserIn |
M. van de Kamp, D. Pokhotelov, K. Kauristie |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 32, no. 12 ; Nr. 32, no. 12 (2014-12-17), S.1511-1532 |
| Datensatznummer |
250121140
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| Publikation (Nr.) |
 copernicus.org/angeo-32-1511-2014.pdf |
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| Zusammenfassung |
Travelling Ionospheric Disturbances (TIDs), which are caused by Atmospheric
Gravity Waves (AGWs), are detected and characterised by a joint analysis of
the results of two measurement techniques: incoherent scatter radar and
multiple-receiver GPS measurements. Both techniques to measure TIDs are
already well known, but are developed further in this study, and the
strengths of the two are combined, in order to obtain semi-automatic tools
for objective TID detection. The incoherent scatter radar provides a good
vertical range and resolution and the GPS measurements provide a good
horizontal range and resolution, while both have a good temporal resolution.
Using the combination of the methods, the following parameters of the TID
can be determined: the time of day when the TID occurs at one location, the
period length (or frequency), the vertical phase velocity, the amplitude
spectral density, the vertical wavelength, the azimuth angle of horizontal
orientation, the horizontal wavelength, and the horizontal phase velocity.
This technique will allow a systematic characterisation of AGW-TIDs, which
can be useful, among other things, for statistical analyses.
The presented technique is demonstrated on data of 20 January 2010 using
data from the EISCAT incoherent scatter radar in Tromsø and from the
SWEPOS GPS network in Sweden. On this day around 07:00–12:00 UT, a
medium-scale TID was observed from both data sets simultaneously. The TID had
a period length of around 2 h, and its wave propagated southeastward with a
horizontal phase velocity of about 67 m s−1 and a wavelength of about 500 km.
The TID had its maximum amplitude in Tromsø at 10:00 UT. The period
length detected from the GPS results was twice the main period length
detected from the radar, indicating a different harmonic of the same wave.
The horizontal wavelength and phase velocity are also estimated from the
radar results using Hines' theory, using the WKB approximation to account
for inhomogeneity of the atmosphere. The results of this estimate are higher
than those detected from the GPS data. The most likely explanation for this
is that Hines' theory overestimated the values, because the atmosphere was
too inhomogeneous even for the WKB approximation to be valid. |
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