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First observations of quasi‐periodic radar echoes from Stanford, California

We present first results from a search for quasi‐periodic (QP) radar echoes in the American sector. These echoes, which are produced by underdense backscatter from field‐aligned irregularities in nighttime midlatitude sporadic E (Es), have been observed in the Asian sector but never before at other longitudes. Using radar data collected during the summer in 1998 from Stanford, California, we show that QP echoes can indeed be detected in the American sector and that they resemble those found in central and southern Japan. We then show that the invariance of a feature in the pattern of QP echoes, which persisted for five hours on 3 August 1998, raises questions regarding the existing models for QP echoes.