Authors: Leo Skaer (University of Hawaii at Manoa), Colby Haggerty (University of Hawaii at Manoa), Jason Tenbarge (Princeton University), Lynn B. Wilson III (NASA GSFC)

Collisionless plasma shocks are a common feature throughout the heliosphere and are important for the evolution of coronal mass ejections and the interaction of the solar wind with Earth’s magnetosphere. Shocks can drive heliospheric turbulence and generate energetic particles, but the dynamics of these shocks are ultimately connected to the small-scale, collisionless plasma physics at the shock front. In-situ observations of shock fronts have revealed the presence of large amplitude electrostatic fluctuations which, to date, have not been reproduced by fully kinetic particle-in-cell (PIC) simulations. In this work, we show that a possible cause for this discrepancy is due to the non-Maxwellian nature of solar wind electrons, i.e., the electron Strahl and halo populations. Using the fully kinetic PIC code, Tristan-MP, we perform 2D shock simulations initialized with a distribution of upstream electrons that more closely resembles the solar wind (i.e. kappa distributions). We find that kappa shock simulations produce larger electrostatic fluctuations at the shock front as compared to the Maxwellian counterpart. We connect this difference to the change in the instabilities triggered by the non-Maxwellian electron distribution. These results have implications for interrupting in-situ shock observations and our understating of collisionless shocks throughout the heliosphere.