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Ann. Geophys., 18, 1224-1230, 2000
www.ann-geophys.net/18/1224/2000/
© European Geosciences Union 2000
Frequency dependent power fluctuations: a feature of the ESR system or physical?
Y. Ogawa1, F. Forme2, and S. C. Buchert1
1Solar-Terrestrial Environment Laboratory, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan
2CETP-Universite Versailles St-Quentin en Yvelines 10-12, Av. de l'Europe, 78140 Velizy, France
Abstract. The k-dependence of the received power in
high signal-to-noise ratio (SNR) conditions, occurring for naturally enhanced
ion-acoustic lines (NEIALs) and for real satellites, is investigated by using
the EISCAT Svalbard Radar (ESR), where the data are recorded in eight separate
channels using different frequencies. For the real satellites we find large
variations of the relative powers from event to event, which is probably due to
a different number of pulses catching the satellite over the integration period.
However, the large power difference remains unexpected in one case. Over short
time scale (< 10 s) the relative power difference seems to be highly
stable. For most NEIAL events the differences between channels are within noise
level. In a few cases variations of the relative power well above both the
estimated and expected 1-sigma level occur over a signal preintegrated profile.
We thus suggest that the frequency dependence of the power in NEIAL events has
its origin in the scattering medium itself as the most plausible explanation.
Key words: Ionosphere (auroral ionosphere; plasma waves
and instabilities; instruments and techniques)
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