The field inside a random distribution of parallel dipoles
  We determine the probability distribution for the field inside a random uniform distribution of electric or magnetic dipoles.   For parallel dipoles, simulations and an analytical derivation show that although the average contribution from any spherical shell around the probe position vanishes, the Levy stable distribution of the field is symmetric around a non-vanishing field amplitude.   In addition we show how omission of contributions from a small volume around the probe leads to a field distribution with a vanishing mean, which, in the limit of vanishing excluded volume, converges to the shifted distribution. 
Janus H. Wesenberg and Klaus Molmer