Solitary Magnetic Structures at Quasi?Parallel Collisionless Shocks: Formation

Solitary magnetic structures known as SLAMS (short large-amplitude structures) have been considered essential elements of collisionless shocks with quasi-parallel geometries. Yet the physics underlying their formation remains an open question. In this paper, we use measurements from magnetospheric multiscale mission combined fully kinetic simulations to study SLAMS. We find that gyro-resonance between solar wind ions and right-hand circularly polarized electromagnetic waves results in field amplification. Gyro-trapping by growing buildup plasma density further enhances current field. The solitary nature stems a beat-like envelope where maximum sets initial location for nonlinear growth. Our present conceptual advance on SLAMS, may shed new light question amplification at astrophysical shocks.