Simulations of Langmuir-wave emission by magnetic holes in the solar wind

Langmuir waves are frequently detected in the solar wind and affect the energetics of the plasma electrons. Previous observational studies have found Langmuir waves associated with magnetic holes in the solar wind. In our work, we aim to understand the connection between magnetic holes and these waves. The Langmuir instability is a well-known consequence of electron beams in plasmas. We use particle-in-cell (PIC) simulations of a collisionless electron-ion plasma in a magnetic hole structure. We study the triggering of Langmuir waves by inhomogeneous beam instabilities in this configuration. Our simulations reveal patterns that suggest that injecting a beam into the magnetic hole has the potential to create spatially inhomogeneous Langmuir wave packets by instability. We support our PIC simulations with linear stability calculations and discuss the conditions required for magnetic holes to emit Langmuir waves through our proposed mechanism. Our simulation results will be used in comparative studies with observational data of Langmuir-wave emitting magnetic holes.