  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 and density scales
of the ISM scattering lenses that are required to explain the magnitude and
dynamical spectrum of the scintillations. In this picture, the parts of warm
ionized interstellar medium that are responsible for the scintillations are
relatively quiescent, with scintillation and scattering resulting from weak
waves propagating along magnetic domain boundary current sheets, which are both
expected from helicity conservation and have 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 3 parameters. Multi-frequency,
multi-epoch low frequency VLBI observations can quantitatively test this
picture. If successful, in addition to mapping the ISM, this may open the door
to precise nanoarcsecond pulsar astrometry, distance measurements, and emission
studies using these 10AU interferometers in the sky.
