Spatial Variation of Rise Time and Dwell Time Induced by a Hypervelocity Impact

Abstract The passage of a shock wave and the following release or rarefaction wave determine the dwell time, how long material remains at high pressure, as a result of a hypervelocity impact. Impact simulations show that the dwell time of high‐velocity ejecta exhibits substantial spatial variation. Here, we expand on this work using high‐resolution numerical simulations (iSALE‐2D) to explore how dwell time varies throughout the shocked region of the target and impactor. Our results reveal that dwell time exhibits significant spatial variation within the target and impactor. For a 10‐km‐diameter impactor the dwell time varies by orders of magnitude, ranging from milliseconds to seconds, for all impact velocities we test (7.5, 13.1 and 20 km ). Regardless of impact velocity, the shortest dwell time appears near the free surface and tends to increase with depth. Additionally, the rise time, which is the time it takes for the pressure to reach its maximum value, also shows considerable spatial variation. In the high pressure ( 25 GPa), shock‐dominant region, the rise time is nearly constant (milliseconds) due to the influence of artificial viscosity. However, in the moderately shocked region ( 25 GPa), the interplay between the faster‐moving elastic wave and the following plastic wave determines the rise time, leading to longer times in regions farther from the impact point.