  An interplanetary (IP) type-II-like radio burst is analyzed. It occurred on
2003 June 17-18 in association with a fast halo coronal mass ejection (CME), an
M6.8 soft-X-ray (SXR) flare, and produced a solar proton event. Unlike coronal
type II bursts and the ma jority of IP type II radio emissions, the IP
type-II-like event associated with the fast halo CME on June 17-18 varies
smoothly in time and frequency and has a frequency bandwidth that is several
times larger than is typical for coronal and IP type II emissions. Moreover,
the frequency change with time is inconsistent with that expected from plasma
radiation associated with a CME-driven shock. I suggest that this IP
type-II-like event, referred to here as an IP type II-S event, is not due to
plasma radiation but, rather, incoherent synchrotron radiation from
near-relativistic electrons entrained in the CME magnetic field, or in the
sheath region between the shock and the CME driver. This event may be an
example of a new and distinct class of interplanetary radio phenomenon.
