AN ALTERNATIVE INTERPRETATION OF THE DOUBLE-RIDGE STRUCTURE IN THEHIGH-FREQUENCY TIME-DISTANCE AUTOCORRELATION FUNCTION?

摘要

It has been reported by Jefferies et al (1997, ApJ 485,rnL49) that the time-distance autocorrelation function, ob-servedrnat frequencies above the atmospheric cut-off fre-quency,rnexhibits a double-ridge structure. They interpretrnthis structure as evidence for chromospheric reflection ofrnhigh-frequency acoustic waves. A closer examination hasrnrevealed, however, that the double ridges may have beenrncaused by interference between wave components abovernand below the acoustic cut-off frequencies, introduced byrna frequency filter that is slightly too broad to keep the lat-terrnout of the analysis. We discuss the implication of thisrnfinding on the interpretation of the double-ridge structure.