Interaction of a strong interplanetary shock with the termination shock

Abstract

The 1991 global merged interaction region (GMIR) shock is a strong forward shock observed from Voyager 2 on day 146 of 1991 at 34.6 AU. As the GMIR shock propagated out‐ward in the distant heliosphere, it eventually encounters the termination shock. We study the interaction of the GMIR shock with the termination shock taking into account the influence of interstellar pickup protons on the solar wind and the shocks. Because the location of the termination shock is an unknown parameter, it remains uncertain about when and where the GMIR shock penetrates through the termination shock. This paper carries out calculations for the interaction to take place over a wide range of possible locations between 70 and 110 AU. The interaction can significantly modify the conditions of both shocks. For the GMIR shock, the interaction can cause a decrease of the shock speed by ∼120 km/s, a decrease of the shock Mach number from ∼1.9 to ∼1.4, and a decrease of the shock strength from ∼2.2 to ∼1.6. For the termination shock, the interaction can cause an increase of the shock speed by ∼95 km/s, a decrease of the shock Mach number from ∼3.6 to ∼2.6, and a decrease of the shock strength from ∼3.2 to ∼2.8.