2D fluid simulations and characterization of ion acoustic solitons

The generation and propagation of solitary ion acoustic waves, or solitons, in the ambient plasma in low Earth orbit (LEO) by charged debris may provide a mechanism for the detection of sub-centimeter scale debris. A two-dimensional (2D) fluid model is used to simulate soliton generation under various plasma parameters and debris characteristics. Both ions and electrons are modeled using a five moment model, coupled through Poisson's equation. The debris is modeled as a charge density source that corresponds to a Gaussian debris potential, traveling at a constant speed through the background plasma. The results show that solitons generated in 2D have lower amplitudes when compared to 1D fluid simulations and 1D solutions to the Korteweg–de Vries equation. While all conditions show the existence of pinned solitons that travel with the debris itself, only a limited range of debris Mach numbers yields precursor solitons. The effects of the debris Mach number, potential, size, and a finite ion temperature are investigated. The transition near the critical Mach number from precursor solitons to pinned solitons is investigated, revealing that precursors are only generated when the local Mach number is less than 1. Numerical probes provide insight into the plasma signatures that can be expected from in situ soliton measurements at various distances from the debris. Finally, two representative sets of conditions that correspond to realistic LEO conditions are used to simulate a space environment where soliton detection could be viable.