Full particle simulations of short large-amplitude magnetric structures (SLAMS) in quasi-parallel shocks.

Dynamics of SLAMS (short large-amplitude magnetic structures) is investigated bythe use of one-dimensional, full particle electromagnetic simulations. As previous hybridsimulations and analysis of experimental observations suggested, present results confirmthat the SLAMS patterns result from the steepening of long wavelength magnetosonicwaves which are excited by diffuse ions (representing the field-aligned reflected ion beam)interacting with the upstream ambient plasma. Five successive phases have been identifiedin the SLAMS dynamics: ULF wave growth and symmetric, asymmetric, spiky, andlate SLAMS. The present accessibility to high-resolution (electron) scales leads to thefollowing new features: (1) the leading edge of the SLAMS steepens over a spatial scalefrom which a large-amplitude whistler precursor is emitted; (2) this whistler departs fromthe SLAMS edge and behaves as a new shock front; (3) the spiky SLAMS phase ischaracterized by the build-up of a strong spiky electrostatic field (its width is about 0.5 ioninertial length) within the whistler precursor and is intermittent with a lifetime lessthan one inverse ion gyroperiod; (4) the new shock front suffers a local self-reformationtypical of a quasi-perpendicular shock in supercritical regime during the late-SLAMSphase. The features of the spiky SLAMS phase can be used as a typical signature in thetime history of the SLAMS dynamics. Spatial/time scales of SLAMS have been measuredthroughout the different phases and are found in good agreement with results issuedfrom previous hybrid simulations and with experimental measurements made by AMPTEUKS/IRM satellites; these are also compared with recent results from Cluster-2 spacemission