Terrestrial Bow Shock Parameters From MMS Measurements: Dependence on Upstream and Downstream Time Ranges

Abstract : We have investigated the dependence of shock parameters (speed vsh, normal (Formula presented.), and angle θBn) on the choice of upstream and downstream regions for 51 bow shock crossings in Magnetospheric Multiscale (MMS) Fast Survey data. We summarize guidelines for selecting stream regions based on the magnetic field and particle moments. Preferred upstream and downstream combinations were identified by minimizing Rankine-Hugoniot conservation errors. Comparing parameters from different upstream/downstream combinations provided a measure of how stream region choices affect the parameters. Shifting from the preferred stream region combination to another would cause <5° change in (Formula presented.) for 90% of shocks, <15 km/s change in vsh of 70% of shocks, and <5° change in θBn for 84% of shocks. All parameters would shift by more than their standard deviations σ. The most robust is (Formula presented.), which would change by <1σ for 22% and <3σ for 86% of shocks, while vsh is the least robust, changing by <3σ for only 12% of shocks. We provide summary plots and detailed lists of parameters in the supporting information.