A solar rotation signature in cosmic dust observed in STEREO spacecraft data

Aims. Cosmic dust within the Solar System is subject to a range of forces that can modify its trajectory, including gravity, radiation pressure, and the Lorentz force. Lorentz force interactions between the solar wind and dust arise due to the motion of charged dust grains with respect to the solar wind plasma flow and the magnetic fields carried by that flow. For dust grains where the charge to mass ratio is sufficiently large, the Lorentz force can significantly modify the dust grain motion. At the same time, properties of the magnetic fields and plasma in the solar wind are modulated by solar periodicities, such as the 11-year solar cycle and the solar rotation period. These solar periodicities are therefore expected to be imparted onto the trajectories of dust moving within the Solar System via Lorentz force interactions. Methods. We examined nearly two decades of cosmic dust observations made by the twin STEREO spacecraft at 1 AU for periodicities in the dust flux. We created a two-dimensional toy model to examine whether it is reasonable to expect solar-rotation variability in solar wind magnetic field and plasma velocities to modify the trajectories of dust that reaches 1 AU. Results. Periodic modulations of the dust flux observed by STEREO at 1 AU are identified near the solar rotation period and its harmonics. The toy model suggests that solar-rotation variability of the solar wind can be sufficient to alter the trajectories of some dust within the Solar System.