Pioneer 8 plasma-wave measurements at distant bow-shock crossings

Enhanced low-frequency (f≃fp+, nfc) plasma-wave levels were detected near the Pioneer 8 multiple bow-shock crossings encountered beyond 120 RE (Bavassano et al., 1971). High-frequency (f≃fp−, fUHR) plasma waves were also detected in the upstream region, and this finding suggests that the distant interaction of the solar wind and the magnetosheath produced nonthermal electrons of the type commonly found upstream from the subsolar shock. The bow-shock position is compared with fluid model predictions, and some distinctions between the standing bow shock and the propagating interplanetary shock are considered.