ULF waves in Earth's foreshock cause the instantaneous angle ϑBn between the upstream magnetic field and the shock normal to deviate from its average value. Close to the quasiparallel (Q∥) shock the transverse components of the waves become so large that the orientation of the field to the normal becomes quasiperpendicular (Q⊥) during applicable phases of each wave cycle. Large upstream pulses of B were observed completely enclosed in excursions of ϑBn into the Q⊥ range. A recent numerical simulation included ϑBn among the parameters examined in Q∥ runs, and described a similar coincidence as intrinsic to a stage in development of the reformation process of such shocks. Thus, the natural environment of the Q∥ section of Earth's bow shock seems to include an identifiable class of enlarged magnetic pulses for which local Q⊥ geometry is a necessary association. ¿ American Geophysical Union 1993