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| Titel |
Classification of X-ray solar flares regarding their effects on the lower ionosphere electron density profile |
| VerfasserIn |
D. P. Grubor, D. M. Šulić, V. Žigman |
| 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 ; 26, no. 7 ; Nr. 26, no. 7 (2008-06-18), S.1731-1740 |
| Datensatznummer |
250016140
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| Publikation (Nr.) |
 copernicus.org/angeo-26-1731-2008.pdf |
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| Zusammenfassung |
The classification of X-ray solar flares is performed
regarding their effects on the Very Low Frequency (VLF) wave propagation
along the Earth-ionosphere waveguide. The changes in propagation are
detected from an observed VLF signal phase and amplitude perturbations, taking
place during X-ray solar flares. All flare effects chosen for the analysis
are recorded by the Absolute Phase and Amplitude Logger (AbsPal), during
the summer months of 2004–2007, on the single trace, Skelton (54.72 N,
2.88 W) to Belgrade (44.85 N, 20.38 E) with a distance along the Great Circle Path
(GCP) D≈2000 km in length.
The observed VLF amplitude and phase perturbations are simulated by the
computer program Long-Wavelength Propagation Capability (LWPC), using Wait's
model of the lower ionosphere, as determined by two parameters: the
sharpness (β in 1/km) and reflection height (H' in km). By varying the
values of β and H' so as to match the observed amplitude and phase
perturbations, the variation of the D-region electron density height profile
Ne(z) was reconstructed, throughout flare duration. The procedure is
illustrated as applied to a series of flares, from class C to M5
(5×10−5 W/m2 at 0.1–0.8 nm), each giving rise to a different time
development of signal perturbation.
The corresponding change in electron density from the unperturbed value at
the unperturbed reflection height, i.e. Ne(74 km)=2.16×108 m−3
to the value induced by an M5 class flare, up to Ne(74
km)=4×1010 m−3 is obtained. The β parameter is
found to range from 0.30–0.49 1/km and the reflection height H' to vary
from 74–63 km. The changes in Ne(z) during the flares, within height
range z=60 to 90 km are determined, as well. |
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