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| Titel |
Comparison between CNA and energetic electron precipitation: simultaneous observation by Poker Flat Imaging Riometer and NOAA satellite |
| VerfasserIn |
Y.-M. Tanaka, M. Ishii, Y. Murayama, M. Kubota, H. Mori, M.-Y. Yamamoto, A. Kadokura, D. Lummerzheim, J. Desrochers, D. S. Evans |
| 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 ; 23, no. 5 ; Nr. 23, no. 5 (2005-07-27), S.1555-1563 |
| Datensatznummer |
250015245
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| Publikation (Nr.) |
 copernicus.org/angeo-23-1555-2005.pdf |
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| Zusammenfassung |
| The cosmic noise absorption (CNA) is compared with the precipitating
electron flux for 19 events observed in the morning sector, using the
high-resolution data obtained during the conjugate observations with the
imaging riometer at Poker Flat Research Range (PFRR; 65.11° N,
147.42° W), Alaska, and the low-altitude satellite, NOAA 12. We
estimate the CNA, using the precipitating electron flux measured by NOAA 12,
based on a theoretical model assuming an isotropic pitch angle distribution,
and quantitatively compare them with the observed CNA. Focusing on the eight
events with a range of variation larger than 0.4dB, three events show high
correlation between the observed and estimated CNA (correlation coefficient
(r0)>0.7) and five events show low correlation (r0<0.5). The
estimated CNA is often smaller than the observed CNA (72% of all data for
19 events), which appears to be the main reason for the low-correlation
events. We examine the assumption of isotropic pitch angle distribution by
using the trapped electron flux measured at 80° zenith angle. It is
shown that the CNA estimated from the trapped electron flux, assuming an
isotropic pitch angle distribution, is highly correlated with the observed
CNA and is often overestimated (87% of all data). The underestimate
(overestimate) of CNA derived from the precipitating (trapped) electron flux
can be interpreted in terms of the anisotropic pitch angle distribution
similar to the loss cone distribution. These results indicate that the CNA
observed with the riometer may be quantitatively explained with a model
based on energetic electron precipitation, provided that the pitch angle
distribution and the loss cone angle of the electrons are taken into
account.
Keywords. Energetic particles, precipitating – Energetic
particles, trapped – Ionosphere-magnetosphere interactions |
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