Shocks in the distant heliosphere

Voyager data are used to study two aspects of pickup proton shocks in the distant heliosphere: (1) Two shocks having similar speed jump of ∼50 km/s observed at 5 AU and at 43 AU demonstrate the effects of pickup protons on weakening interplanetary shocks at increasing heliocentric distance. (2) On the basis of three shocks identified outside 34 AU from high‐resolution plasma and magnetic field data we develop an empirical model to study the jump conditions of pickup protons across solar wind shocks. Making use of the empirical model one can study the postshock conditions of pickup protons for the global merged interaction region (GMIR) shock and the termination shock; this will enable us to calculate more accurately the propagation of the GMIR shock and the interaction of GMIR shock with the termination shock. We also find that the variation of the pickup proton temperature TI across the shock is very close to the adiabatic relation that TI is proportional to the magnetic field strength B.