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| Titel |
Ionospheric Scintillation at Low Frequencies: Broadband Spectra and Phase Measurements from Natural Radio Sources |
| VerfasserIn |
Richard A. Fallows, Biagio Forte, William A. Coles |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250127181
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| Publikation (Nr.) |
 EGU/EGU2016-7024.pdf |
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| Zusammenfassung |
| Observations of strong natural radio sources such as Cassiopeia A taken using the Low
Frequency Array (LOFAR) centred on the Netherlands, and the Kilpisjärvi Atmospheric
Imaging Receiver Array (KAIRA) in arctic Finland, over the frequency range 10-250 MHz
show almost continual ionospheric scintillation. Dynamic spectra of these observations show
scintillation varying from weak to strong scattering and the effects of refraction due
to large-scale structure in the ionosphere can also be visible. Recent efforts have
also attempted to measure phase scintillation in addition to the regular intensity
measurements, using simultaneous low-resolution all-sky imaging, to confirm when strong
refraction is seen. Delay-Doppler spectra (the two-dimensional power spectrum of a
dynamic spectrum) sometimes show an arc structure, similar to the “scintillation arcs”
reported from observations of interstellar scintillation, which can be used to model
parameters such as the distance to the scattering “scree” and the velocity of the
scattering medium transverse to the line of sight. These two parameters are inherently
linked in modelling which means that one needs to be known before the other can
be established accurately. The dense core of the LOFAR array has been used to
take temporal cross-correlations between station pairs to establish a picture of the
velocity field in the ionosphere; with KAIRA other supporting instrumentation can be
used to estimate ionospheric velocities in nearby regions. These velocities are used
to attempt to establish the altitudes dominating scattering due to the ionosphere. |
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