Observations of large-amplitude electromagnetic waves and associated wave–particle interactions at the dipolarization front in the Earth's magnetotail: A case study

•Larger-amplitude electromagnetic waves were observed at DF.•Electromagnetic waves belong to Ion Bernstein mode or current-driven ion cyclotron mode.•The observed electromagnetic waves cannot accelerate the protons at the survival timescale of the DFs and the waves.

Broadband frequency waves around the dipolarization front (DF) are believed to play a crucial role in the particle dynamics. Using the Cluster observations, we report in this study large-amplitude electromagnetic waves with frequencies just above the ion cyclotron frequency at the DF in the near-Earth magnetotail region. The waves have very large amplitudes of magnetic and electric field fluctuations, up to ~2 nT and ~10 mV/m, respectively. The magnetic fluctuations are predominately along the ambient magnetic field (B0), while the electric fluctuations are primarily perpendicular to B0. The observed waves are highly oblique with a propagation angle of ~100° with respect to the ambient magnetic field, and are also linearly polarized. These features are consistent with the properties of the ion Bernstein wave mode in the high plasma β region, and also with the properties of current-driven ion cyclotron waves driven by the electromagnetic current-driven Alfven instability. We also discuss the possibility of wave–particle interactions at the DF.