Causes of spectral enhancements in solar wind power spectra

Enhancements in power spectra of solar wind ion flux in the frequency neighborhood of 0.5 Hz had been noted by Unti et al. (1973). It was speculated that these were due to convected small-scale density irregularities. In this paper 54 flux spectra, calculated from Ogo 5 data are examined. It is seen that the few prominent spectral peaks which occur were not generated by density irregularities but were due to several different causes, including convected discontinuities and propagating transverse waves. A superposition of many spectra, however, reveals a moderate enhancement at a frequency corresponding to convected features with a correlation length of a proton gyroradius, consistent with the results of Neugebauer (1975)