AbstractWe report low‐frequency magnetic waves that were observed by the Advanced Composition Explorer (ACE) spacecraft on day of year 180 of 1999 with characteristics consistent with the predictions of waves excited by newborn interstellar pickup He+ ions. This event was found by examining daily spectrograms of MAG data, a new data product that is now available to the community via the ACE Science Center. The event shown here is one of approximately 20 similar events that will be analyzed in future studies. This event is fairly typical of those we have found so far. The waves exist at spacecraft‐frame frequencies between the He+ cyclotron frequency and approximately twice the H+ cyclotron frequency. Fluctuations are transverse to the mean magnetic field, are noncompressive, circularly polarized, have field‐aligned minimum variance directions, and are left‐hand polarized in the spacecraft frame as predicted by theory. The event lasts for just under 1 h.
