Modeling Torque Induced Alignment in Dusty Plasma System

Dusty plasmas, composed of micron-sized particles that become charged and interact with their plasma environment, provide a unique setting to explore the dynamics of strongly coupled systems. In this work, we investigate how irregular dust aggregates rotate and align when exposed to streaming ions and an external electric field. Since natural dust grains are often asymmetric, their shape significantly affects how they interact with electric and drag forces. Reproducing these complex shapes in laboratory conditions is challenging, so we model them as rigid aggregates made of spherical monomers, a simplified but effective approach that preserves essential physical features. These aggregates experience a combination of torques, originating from electric forces, ion flow, neutral drag, and thermal motion, that drive their rotational dynamics and determine their eventual orientation relative to the plasma environment.

In our study, we simulate dust aggregates with different shapes, from elongated to nearly spherical under a range of external electric field strengths. We analyze the torques acting on them, including those from the electric field, ion flow, neutral drag, and thermal fluctuations, to identify which ones play the leading role in determining their final orientation. As the system evolves, we track how the angular velocity changes over time until the aggregates reach a stable rotational state. Once this equilibrium is achieved, we examine how the electric dipole moment aligns with the external field and calculate the interaction energy as a function of the dipole’s orientation. This allows us to map out the potential landscape and how stable each orientation is. By comparing results across different field strengths and aggregate shapes, we gain a clearer picture of the mechanisms that drive alignment and stability in these systems. These insights are not only relevant for laboratory experiments, but also for understanding the behavior of charged grains in space, such as in planetary rings or interstellar clouds.