An Investigation of Ion Cyclotron Wave Storms at 1 AU

Strong narrow-band ion cyclotron waves (ICWs) are observed sporadically in the solar wind in the inner heliosphere. They are observed to be nearly circularly polarized, with magnetic perturbations transverse to the background magnetic field. The fluctuations propagate close to the direction of the background magnetic field. At times, these fluctuations appear as ICW storms lasting tens of minutes. Analysis of a one-year survey of ICW storms using STEREO A data, indicates that the distribution of ICW storms does not align with the focusing cone of interstellar neutrals and the fluctuations are unlikely to result from interaction involving the pickup of interstellar neutrals. In this study, we investigate other scenarios: local generation through ion cyclotron instability or beam instability. The Wind and Cluster spacecraft have provided high-resolution magnetic and electric field data, as well as temperature anisotropies for protons and ions. We use them to study the variation in wave parameters of ICW storms with solar wind plasma conditions. This investigation will enhance our understanding of the generation of the ICWs and their interaction with particles in the solar wind.