  In order to explain rapid light curve variability without invoking a variable
source, several authors have proposed "minijets" that move relativistically
relative to the main flow of the jet. Here we consider the possibility that
these minijets, instead of being isotropically distributed in the comoving
frame of the jet, form primarily perpendicular to the direction of the flow, as
the jet dissipates its energy at a large emission radius. This yields two
robust features. First, the emission is significantly delayed compared with the
isotropic case. This delay allows for the peak of the afterglow emission to
appear while the source is still active, in contrast to the simplest isotropic
model. Secondly, the flux decline after the source turns off is steeper than
the isotropic case. We find that these two features are realized in gamma-ray
bursts (GRBs): 1. The peak of most GeV light curves (ascribed to the external
shock) appears during the prompt emission phase. 2. Many X-ray light curves
exhibit a period of steep decay, which is faster than that predicted by the
standard isotropic case. The gamma-ray generation mechanism in GRBs, and
possibly in other relativistic flows, may therefore be anisotropic.
