Modelling the variance of dispersion measures of radio pulsars

Abstract

On the basis of a highly simplified model for small scale structure in the electron density distribution in the Galaxy, we argue that the spread of expectation values for the dispersion measure at given distance is proportional to the square root of the dispersion measure as found from a smooth model for the electron distribution. We show that this simple method leads to appreciable improvement in the description of dispersion measures in a full population synthesis.