Spontaneous Hot Flow Anomalies at Earth’s foreshock.

In recent years we have learnt that foreshock transients play an influential role in solar wind coupling with Earth’s magnetosphere. These transients include Spontaneous Hot Flow Anomalies (SHFAs) which are characterized by dips in magnetic field magnitude and ion density, enhanced temperature, and are surrounded by ultra low frequency waves. SHFAs share some characteristics with hot flow anomalies but their formation mechanism does not require a discontinuity in the solar wind.  SHFAs evolve from caviton interaction with backstreaming ions. We use Cluster and MMS magnetic field and plasma data to study SHFAs internal structure and their evolution. We find that SHFA can occur not only deep in the foreshock as initially thought, but they can also been observed near the foreshock boundary where higher frequency waves (f ∼ 1 Hz) exist. We also investigate the properties of velocity distribution functions inside these transients, and their influence on bow shock structure.