Investigation of  ∼ 20–40 mHz ULF waves and their driving mechanisms in Mercury's dayside magnetosphere

Abstract. Ultra-low-frequency (ULF) waves in the  ∼  20–40 mHz range are frequently observed in the Mercury magnetosphere using Mercury Surface Space Environment Geochemistry, and Ranging (MESSENGER) magnetic field data. The majority of these waves have very similar characteristics to the waves likely driven by Kelvin–Helmholtz (KH) ULF waves (which are retained as a subset of the wave events studied in this paper) identified in a previous study. Significant ULF wave activity is observed in the dawn sector of the magnetosphere. This indicates that Mercury KH waves may be more common between 6 and 12 magnetic local time than previously predicted and that magnetospheric ULF waves in the frequency band  ∼ 20–40 mHz can be used as a detection tool for Hermean KH waves.