TEMPORAL VARIATIONS IN THE TERMINATION SHOCK DISTANCE

A kinematic analysis is made of solar wind driven temporal variations in the heliospheric termination shock distance. This has become possib le because the large-scale dynamics of, and temporal variations in the distant solar wind are now well enough known from a combination of in situ and remote measurements. Conversely, nothing is known of the cor responding properties in the local interstellar medium, and hence thes e will be ignored. Given specific assumptions for how the termination shock responds to solar wind fluctuations, it is shown that the termin ation shock is very agile, moving in and out by up to a few AU in a mo nth. This conclusion holds for a broad range of shock response assumpt ions. Because a spacecraft moves slowly in comparison to the terminati on shock, the shock will sweep back and forth over the spacecraft once the shock is first encountered.