How to define the interplay between different instabilities excited within the foot of a supercritical shock : 2D PIC simulations

<p>In supercritical shocks a substantial fraction of ions is reflected at the steep shock ramp. The beam of reflected ions carries a&#160;considerable amount of energy and momentum. As a consequence, different plasma populations can co-exist within the same foot region, which constitutes a source of micro-instabilities excited by the relative drifts between incoming ions, reflected ions, and electrons&#160;across the ambient magnetic field <strong>B_o&#160;</strong>. With the help of a spectral periodic 2D PIC code, we investigate the resulting micro-turbulence.&#160;Three different waves with different frequency/wave number ranges can be excited simultaneously: Bernstein waves and whistler waves&#160;near the lower-hybrid frequency as well as the electron cyclotron frequency. The present work is a 2D extension of a previous analysis&#160;(Muschietti et Lembege, Ann. Geophys. 2017) and allows to self-consistently include the mutual interaction between the different instabilities/waves&#160;which propagate in different directions with respect to <strong>B_o</strong> and are at different stages of their respective linear/nonlinear phases. In order to clarify their intricate synergies, a new filtering procedure (low or high pass filter of a given wave number range)&#160;has been developed. Taking thus advantage of the spectral nature of the code, we can include/exclude at will the impact of a given instability&#160;on the other ones. We have performed several times the simulation with exactly the same initial conditions yet with different filtering ranges.&#160;The procedure allows us to illuminate the role played by each instability in the scenario when all are included. Recent results will be presented.&#160;</p>