In recent years we have learnt that foreshock transients play an influential role in the solar wind coupling with the Earth’s magnetosphere. Such transients include cavitons and Spontaneous Hot Flow Anomalies (SHFAs) both of which are characterized by dips in magnetic field magnitude and ion density, and are surrounded by ultra low frequency waves. While the temperature is increased and the speed is diminished inside SHFAs, these two parameters do not change inside cavitons. Previous works have shown that cavitons form by wave interaction upstream from the bow shock, and that SHFAs evolve from caviton interaction with backstreaming ions. In this work we use Cluster and MMS magnetic field and plasma data to study caviton and SHFA internal structure and their evolution. We also investigate the properties of velocity distribution functions inside these transients, and their influence on the bow shock structure.

The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)