In this paper we generalize earlier gasdynamic analyses of the motion
of the heliospheric termination shock in response to upstream disturba
nces (Barnes, 1993, 1994; Naidu and Barnes, 1994), to include magnetoh
ydrodynamic (MHD) phenomena. We assume that the termination shock is a
strong, perpendicular shock and that the initial upstream disturbance
is a tangential discontinuity. The resulting configuration after the
interaction is very similar to that in the gasdynamic models after an
interaction with a contact discontinuity or interplanetary shock, and
for an increase (decrease) in dynamic pressure consists of an outward
(inward) propagating termination shock and an outward propagating shoc
k (MI-ID rarefaction wave) that carries the signal of the disturbance
into the far downstream plasma. The plasma immediately behind the new
termination shock is separated from the downstream signal by a tangent
ial discontinuity. The results of the model show that the speed of the
new termination shock depends mainly on the magnitude of the change i
n dynamic pressure and are typically of order similar to 100 km/s, com
parable to the results of the gasdynamic models.