[en] Solar wind data that have been collected by earth-orbiting satellites are likely to be contaminated a significant part of the time by the proximity of the bow shock. Heating of the electron component in the shock-perturbed region is well established, whereas a temperature increase of the ion component has not been observed in the past.A statistical study of the data measured aboard the Heos 2 satellite during the period February 1972 to August 1974 is presented. Employing T/sub parallel/B²/n² as an indicator, the geometry and extent of the upstream proton-heating zone and its relation to the bow shock is investigated. The heating process is found to be more effective nearer the shock than farther away. When the analysis is restricted to data that have been measured not more than 10 R/subE/ from the bow shock and calculate mean values, an increase of 47% in T/sub parallel/B²/n², an increase of 10% in T/sub parallel/, and a simultaneous decrease of 13% in proton number density n are found for shock-perturbed conditions relative to unperturbed conditions. All the other parameters, especially T/sub perpendicular//B, remain unaffected within statistical errors