ALTITUDE INTEGRATION EFFECTS IN THE SKEWNESS OF TYPE-2 COHERENT ECHOES

Possible effects of signal reception from different electrojet heights in a skewness of auroral coherent spectra are studied assuming that t he ''inherent'' spectral line due to plasma turbulence is of type-2 an d symmetrical. For reasonable ionospheric parameters, the altitude int egrated spectra are expected to be skewed negatively for positive mean Doppler shift, in agreement with radar observations at small aspect a ngles. However, the spectra could be skewed positively if the turbulen t layer or the electron density profile is shifted to high altitudes o f similar to 120 km. This change of spectral shape will not be observe d experimentally if, at the same time, either the electron collision f requency is enhanced or the ''inherent'' spectral width is increased. Observational results are discussed in view of the predictions given.