UVCSWLC observations of compressional waves in the south polar coronal hole

Recent SOHO Ultraviolet Coronagraph Spectrometer (UVCS) white light channel (WLC) observations of the south polar coronal hole plumes and interplume r egions produce signatures of quasi-periodic variations in the polarized bri ghtness (pB) at a heliocentric distance of 1.9 solar radii (R.). The Fourie r power spectrum of the pB time series shows significant peaks at about 1.6 -2.5 mHz and additional smaller peaks at longer and shorter timescales. Wav elet analysis of the pB time series shows that the coherence time of the fl uctuations is about 30 minutes. The new observations strongly suggest that the fluctuations are compressional wave packets propagating in the coronal hole high above the limb. The presence of compressional waves may have impo rtant implications that help to explain the heating of coronal holes and th e fast solar wind acceleration.