Simulations underestimate wave amplitudes during magnetic reconnection*

Collisionless plasma systems are often studied using fully kinetic simulations, where protons and electrons are treated as particles. Due to their computational expense, it is necessary to reduce the ion-to-electron mass ratio mi/me or the ratio between plasma and cyclotron frequencies in simulations of large systems. In this work we show that when electron-scale waves are present in larger-scale systems, numerical parameters affect their amplitudes. Using lower-hybrid drift waves during magnetic reconnection as an example, we find that the ratio between the wave electric field and the reconnection electric field scales like $sqrt(mi/me)$, meaning that typical simulations underestimate its contribution. Furthermore, the anomalous drag that contributes to momentum balance is found to be underestimated by an order of magnitude. The results suggest caution when interpreting the results of kinetic simulations, and may be relevant to other systems such as collisionless shocks