Statistical study of SLAMS at the Martian foreshock

Properties of the region upstream of planetary bow shocks depend strongly on the direction of the interplanetary magnetic field. For quasi-parallel bow shocks, part of the solar wind ions are reflected back upstream from the shock and this reflected ion population triggers instabilities resulting in a turbulent region. In the quasi-parallel case, reflected particles travel far upstream, creating an extended turbulent foreshock region. Within this region, Short Large-Amplitude Magnetic Structures (SLAMS) can frequently be found, which are suggested to play a pivotal role in the formation of planetary bow shocks. Yet many properties of SLAMS are not well known at Earth and even less so at other planets.

Here we present results on the occurrence and other properties of SLAMS at the Martian foreshock with the help of magnetic field and ion data from NASA's Mars Atmosphere and Volatile Evolution Mission (MAVEN). SLAMS are identified by three criteria. First, a magnetic field three times stronger than the background magnetic field is required. Second, SLAMS should have an elliptic polarization so that it can be differentiated from a shock oscillation. Last, it takes place upstream of the bow shock. The results presented here can offer comparative insights with SLAMS at Earth for exploring potential dependencies on system size and other magnetospheric parameters.