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| Titel |
D-region electron density and effective recombination coefficients during twilight – experimental data and modelling during solar proton events |
| VerfasserIn |
A. Osepian, S. Kirkwood  , P. Dalin, V. Tereschenko |
| 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 ; 27, no. 10 ; Nr. 27, no. 10 (2009-10-02), S.3713-3724 |
| Datensatznummer |
250016663
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| Publikation (Nr.) |
 copernicus.org/angeo-27-3713-2009.pdf |
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| Zusammenfassung |
| Accurate measurements of electron density in the lower D-region (below 70 km
altitude) are rarely made. This applies both with regard to measurements by
ground-based facilities and by sounding rockets, and during both quiet
conditions and conditions of energetic electron precipitation. Deep
penetration into the atmosphere of high-energy solar proton fluxes (during
solar proton events, SPE) produces extra ionisation in the whole D-region,
including the lower altitudes, which gives favourable conditions for accurate
measurements using ground-based facilities. In this study we show that
electron densities measured with two ground-based facilities at almost the
same latitude but slightly different longitudes, provide a valuable tool for
validation of model computations. The two techniques used are incoherent
scatter of radio waves (by the EISCAT 224 MHz radar in Tromsø, Norway,
69.6° N, 19.3° E), and partial reflection of radio-waves (by
the 2.8 MHz radar near Murmansk, Russia, 69.0° N, 35.7° E).
Both radars give accurate electron density values during SPE, from heights
57–60 km and upward with the EISCAT radar and between 55–70 km with the
partial reflection technique. Near noon, there is little difference in the
solar zenith angle between the two locations and both methods give
approximately the same values of electron density at the overlapping heights.
During twilight, when the difference in solar zenith angles increases,
electron density values diverge. When both radars are in night conditions
(solar zenith angle >99°) electron densities at the overlapping
altitudes again become equal. We use the joint measurements to validate model
computations of the ionospheric parameters f+, λ, αeff
and their variations during solar proton events. These parameters are
important characteristics of the lower ionosphere structure which cannot be
determined by other methods. |
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