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| Titel |
A quantitative analysis of the diurnal evolution of Ionospheric Alfvén resonator magnetic resonance features and calculation of changing IAR parameters |
| VerfasserIn |
S. R. Hebden, T. R. Robinson, D. M. Wright, T. Yeoman, T. Raita, T. Bösinger |
| 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 (2005-07-28), S.1711-1721 |
| Datensatznummer |
250015259
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| Publikation (Nr.) |
 copernicus.org/angeo-23-1711-2005.pdf |
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| Zusammenfassung |
| Resonance features of the Ionospheric Alfvén Resonator (IAR) can be
observed in pulsation magnetometer data from Sodankylä, Finland using
dynamic spectra visualizations. IAR resonance features were identified on 13
of 30 days in October 1998, with resonance structures lasting for 3 or more
hours over 10 intervals. The diurnal evolution of the harmonic features was
quantified for these 10 intervals using a manual cursor-clicking technique.
The resonance features displayed strong linear relationships between
harmonic frequency and harmonic number for all of the time intervals
studied, enabling a homogeneous cavity model for the IAR to be adopted to
interpret the data. This enabled the diurnal variation of the effective size
of the IAR to be obtained for each of the 10 time intervals. The average
effective size was found to be 530 km, and to have an average variation of
32% over each time interval: small compared to the average variation in
Alfvén velocity of 61%. Thus the diurnal variation of the harmonics
is chiefly caused by the changing plasma density within the IAR due to
changing insolation. This study confirms Odzimek (2004) that the dominating
factor affecting the IAR eigenfrequencies is the variation in the Alfvén
velocity at the F-layer ion-density peak, with the changing IAR size
affecting the IAR eigenfrequencies to a smaller extent. Another IAR
parameter was derived from the analysis of the IAR resonance features
associated with the phase matching structure of the standing waves in the
IAR. This parameter varied over the time intervals studied by 20% on
average, possibly due to changing ionospheric conductivity.
Keywords. Ionosphere (Auroral ionosphere;Wave propagation)
– Radio science (Electromagnetic noise and interference) |
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