  Recent advances in early detection and detailed monitoring of GRB afterglows
have revealed variability in some afterglow light curves. One of the leading
models for this behavior is the patchy shell model. This model attributes the
variability to random angular fluctuations in the relativistic jet energy.
These an-axisymmetric fluctuations should also impose variations in the degree
and angle of polarization that are correlated to the light curve variability.
In this letter we present a solution of the light curve and polarization
resulting from a given spectrum of energy fluctuations. We compare light curves
produced using this solution to the variable light curve of GRB 021004 and we
show that the main features in both the light curve and the polarization
fluctuations are very well reproduced by this model. We use our results to draw
constraints on the characteristics of the energy fluctuations that might have
been present in GRB 021004.
