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D.R. Stinebring, K.M. Becker, J.E. Espinoza Goodman, M.A. Kramer, J.L. Sheckard (Oberlin), J.M. Cordes, M.A. McLaughlin (Cornell)
We have made pulsar dynamic spectra observations with the upgraded Arecibo telescope and a new, high-resolution spectrometer (AOFTM). The combination of Arecibo's sensitivity and the 10~kHz resolution, 10~MHz bandwidth, and 0.1 ms time resolution of these observations have uncovered intriguing new phenomena. In one case we find a dynamic spectrum that lacks isolated regions of scintillation maxima and, instead, has a dense, intertwined pattern of maxima and minima. In several other cases we have found well-defined wisp-like patterns of fluctuation power in a power-spectrum analysis of the dynamic spectra. The narrowness of these features and their low power level (at least 30 dB below the main diffractive feature) are remarkable. We are employing a ray-tracing simulation to guide us in interpretation of these spectra. We are using this simulation to identify the scattering geometry needed to explain the observations. We will present results of the observations and the simulation at the meeting. This research was supported in part by the National Science Foundation through grant AST-9619493 and through its support of the National Astronomy and Ionosphere Center.
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