The ICE spacecraft observed in the vicinity of comet Giacobini-Zinner electrostatic noise with burstlike features seemingly modulated by the relative orientation of the interplanetary magnetic field and the solar wind velocity (Richardson et al., this issue). We discuss the adequacy of ion acoustic-like instabilities stimulated by photoelectron or newborn ion beams to the interpretation of the electrostatic bursts, and we conclude that the mode fed by the photoelectrons exhibits characteristics compatible with the observations. ¿ American Geophysical Union 1989