Nonstationarity of strong collisionless quasiperpendicular shocks: Theory and full particle numerical simulations

Vladimir Krasnoselskikh (1) , Bertrand Lembège (2) , P. Savoini (2) , V. V. Lobzin (1)

1 LPCE - Laboratoire de physique et chimie de l'environnement
2 CETP - Centre d'étude des environnements terrestre et planétaires

Whistler waves are an intrinsic feature of the oblique quasiperpendicular collisionless shock waves.For supercritical shock waves, the ramp region, where an abrupt increase of the magnetic fieldoccurs, can be treated as a nonlinear whistler wave of large amplitude. In addition, oblique shockwaves can possess a linear whistler precursor. There exist two critical Mach numbers related to thewhistler components of the shock wave, the first is known as a whistler critical Mach number andthe second can be referred to as a nonlinear whistler critical Mach number. When the whistlercritical Much number is exceeded, a stationary linear wave train cannot stand ahead of the ramp.Above the nonlinear whistler critical Mach number, the stationary nonlinear wave train cannot existanymore within the shock front. This happens when the nonlinear wave steepening cannot bebalanced by the effects of the dispersion and dissipation. In this case nonlinear wave train becomesunstable with respect to overturning. In the present paper it is shown that the nonlinear whistlercritical Mach number corresponds to the transition between stationary and nonstationary dynamicalbehavior of the shock wave. The results of the computer simulations making use of the 1D fullparticle electromagnetic code demonstrate that the transition to the nonstationarity of the shock frontstructure is always accompanied by the disappearance of the whistler wave train within the shockfront. Using the two-fluid MHD equations, the structure of nonlinear whistler waves in plasmas withfinite beta is investigated and the nonlinear whistler critical Mach number is determined. It issuggested a new more general proof of the criteria for small amplitude linear precursor or wakewave trains to exist

Domaines: Planète et Univers [physics]

Vladimir Krasnoselskikh, Bertrand Lembège, P. Savoini, V. V. Lobzin. Nonstationarity of strong collisionless quasiperpendicular shocks: Theory and full particle numerical simulations. Physics of Plasmas, 2002, 9 (4), pp.1192-1209. ⟨10.1063/1.1457465⟩. ⟨insu-02928445⟩