  The coagulation of cosmic dust grains is a fundamental process which takes
place in astrophysical environments, such as presolar nebulae and circumstellar
and protoplanetary disks. Cosmic dust grains can become charged through
interaction with their plasma environment or other processes, and the resultant
electrostatic force between dust grains can strongly affect their coagulation
rate. Since ions and electrons are collected on the surface of the dust grain
at random time intervals, the electrical charge of a dust grain experiences
stochastic fluctuations. In this study, a set of stochastic differential
equations is developed to model these fluctuations over the surface of an
irregularly-shaped aggregate. Then, employing the data produced, the influence
of the charge fluctuations on the coagulation process and the physical
characteristics of the aggregates formed is examined. It is shown that dust
with small charges (due to the small size of the dust grains or a tenuous
plasma environment) are affected most strongly.
