HELIOSPHERIC TERMINATION SHOCK MOTION IN RESPONSE TO LISM VARIATIONS - SPHERICALLY SYMMETRICAL MODEL

The unsteady spherically symmetric one-dimensional gasdynamic model ap pears to be a powerful tool in the investigation of the termination sh ock motion. Such a model has previously been used to examine the respo nse of the heliospheric termination shock to variations in upstream so lar wind conditions [Ratkiewicz et al., 1996]. In the current paper we apply the same model to study response of the shock to variations in the interstellar medium. The initial-boundary conditions for the unste ady calculations are given by the pressure as a function Of time on an outer boundary either alone or with the density as a function of time on an inner boundary. The motion of the termination shock is caused b y fluctuations in both solar wind and interstellar plasma parameters a nd has a rather complicated behavior, characterized by a sequence of p erturbations that hit the termination shock and are reflected from the outer boundary.