Pulsar Scintillation Arcs. I. Frequency Dependence

Abstract

Dynamic spectra of pulsars often showlow-level crisscross patterns as well as isolated interference maximacalled scintles. Previously, we have shown that a power spectrumanalysis of the dynamic spectrum usually exhibits a parabolic arc witha well-determined curvature. A simple analysis predicts that thiscurvature should scale with observing frequency as nu -2. Wereport on multifrequency observations of three pulsars at the AreciboObservatory that are designed to test this prediction and explore thefrequency behavior of the power distribution. We find that the arccurvature scales as expected over more than a factor of 5 in observingfrequency (0.43-2.2 GHz). This allows us to compare arc curvature atdifferent frequencies obtained over a long time span. Furthermore, wefind that scintillation arcs are a broadband phenomenon: they arepresent contemporaneously, and with the same general appearance,over a wide frequency range. At higher frequencies (>~1 GHz) thearcs are more sharply defined, substructure is more prominent, andinverted subarcs often appear with vertices along the main parabola.