Abstract
<strong class="journal-contentHeaderColor">Abstract.</strong> 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 (<u><</u> 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.<br><br><b>Key words: </b>Ionosphere (auroral ionosphere; plasma waves and instabilities; instruments and techniques)
Highlights
Incoherent scatter (IS) radar signals sometimes show spectra which cannot be explained by the IS theory
In the following we investigate whether these power dierence are related to the occurrence of high signal-to-noise ratio (SNR) or perhaps an inherent feature of naturally enhanced ion-acoustic lines (NEIALs)
Thin points are from normal IS signals, and thick ones at the high SNR are from ranges with power enhancements from NEIALs
Summary
Incoherent scatter (IS) radar signals sometimes show spectra which cannot be explained by the IS theory. These spectra have enhanced power at the ion acoustic frequency, they are called naturally enhanced ion-acoustic lines (NEIALs). Rietveld et al (1991) presented a systematic study of NEIALs received by the EISCAT UHF system. Several models to explain NEIALs have been proposed such as the current driven
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