Lomb‐Scargle periodograms clearly show the presence of periodicities withT≈ 150 days in the Voyager 2 plasma bulk‐speed and density data. In this paper wavelet analysis is employed to investigate the time‐variation of these periodicities. It is shown that the 142 day signal is a low‐power but persistent signal requiring unusually (temporally) large wavelets to detect significant power. An episode of significant 142 day periodicity is found in the speed data around 1982 and two significant episodes are found in the density data around 1983 and 1990. There may also be a significant episode developing in the density data in recent (2003) data along with a possible relation to solar activity. © 2004 American Institute of Physics