Structure and properties of the termination shock

Conventionally, the heliospheric termination shock (HTS) is regarded as a sharp MHD discontinuity. More recent models suggest that the back‐reaction of energetic cosmic rays accelerated at the HTS will create a broad shock with an extended precursor. Here we suggest that a combination of upstream solar wind disturbances interacting with the HTS, the presence of cosmic ray gradient‐driven instabilities and their coupling to the pickup ion population yields a termination shock that is highly dynamical in both structure and location. We also suggest that the diffusive cosmic ray transport equation used to model particle acceleration at a shock may require modification to account for a highly turbulent velocity component.