Pulsar scintillations from corrugated reconnection sheets in the interstellar medium

Abstract

We show that surface waves along interstellar current sheets closely aligned with the line of sight lead to pulsar scintillation properties consistent with those observed. This mechanism naturally produces the length-scales and density scales of the interstellarmedium (ISM) scattering lenses that are required to explain the magnitude and dynamical spectrum of the scintillations. In this scenario, the parts of warm ionized ISM that are responsible for the scintillations are relatively quiescent, with scintillation and scattering resulting from weak waves propagating along magnetic domain boundary current sheets. These are expected from helicity conservation and have also been observed in numerical simulations. The model statistically predicts the spacing and amplitudes of inverted parabolic arcs seen in Fourier-transformed dynamical spectra of strongly scintillating pulsars with only three parameters. Multifrequency, multi-epoch low-frequency very long baseline interferometry observations can quantitatively test this. If successful, in addition to mapping the ISM, this might allow precise nanoarcsecond pulsar astrometry, distance measurements and emission studies using these 10-au interferometers in the sky. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.