Properties of low frequency electromagnetic waves at comet Grigg-Skjellerup

In this paper by using the minimum variance method and cross correlation analysis, we analyze the data of magnetic field and electron flux obtained by the spacecraft Giotto at comet P/Grigg-Skjellerup. The results show that there exist a large amount of low frequency waves for a weakly active comet, at frequencies close to the local water group ion cyclotron frequencies. These low frequency left-handed electromagnetic waves are generated by cometary newborn ring ions. The direction of propagation is not exactly parallel to the magnetic field direction, but not far from it. Cross-analysis of the electron parameters with the magnetic field reveals the existence of a compressive wave component even at large distance from the nucleus.