Multiple Scintillation Arcs in Six Pulsars

Abstract

Low-intensity scattering in discrete screens gives rise to parabolic scintillation arcs in pulsar secondary spectra. The curvature of the arc boundary is uniquely determined by the location of the screen along the line of sight, the distance to the pulsar, and the relative velocity of pulsar and Earth (assuming the transverse screen velocity to be small). This information is usually available for the strong pulsars needed to exhibit clear scintillation arcs. Early studies reported single arcs along most lines of sight. This seemed puzzling given the variety of distances and sight lines being probed. We report new, higher sensitivity observations that show up to four scintillation arcs for a particular sight line.