Scales at High Mach Number Quasiperpendicular Shocks and Problem of Electron Heating

1. Scales at High Mach Number Quasiperpendicular Shocks and Problem of Electron Heating Vladimir KRASNOSELSKIKH LPC2E / CNRS-University of Orleans S.J. Schwartz, D. Sundqvist, F. Mozer

2. Electron Heating Scale at High Mach Number Quasiperpendicular Shocks Plan Introduction • Shock front structure • Small scale structure of the electric and magnetic fields • Scale of electron heating 4. Conclusions

3. Collisionless shocks : Critical questions

4. Collisionless shocks : new results from ClusterEarth’s bow shock Tsurutani and Rodriguez, 1981

5. Solar wind Magnetospheric regions studied by Cluster Polar cusp Bow shock Auroral zone Plasmasphere Magnetopause

14. Initial idea of the shock front structure: dispersion versus nonlinearity in the presence of the weak dissipationPrecursors in sub-critical shocks and early models (Sagdeev, 1961, 1964)The structure is formed as a result of counter-balance between nonlinearity and dispersion in the presence of the weak dissipation

15. Quasiperp Shock profile (heritage of ISEE)

16. As supposed for subcritical shocks

17. ISEE and simulations: supercritical quasi-perpendicular shocks: the dissipation is due to reflected ionsHow does it change the role of the dispersion and nonlinearity?

19. If shock structure is similar to dispersive nonlinear waves then Phase velocity dependence of oblique fast magnetosonic (whistler) waves upon the wavenumber

20. Galeev et al., 1988 a,b,c; Krasnoselskikh et al. 2002 Gradient catastrophe of nonlinear upstream whistler Above whistler critical Mach number whistler precursor becomes nonlinear Nonlinear whistler critical Mach number Above Mnw shock nonlinear steepening of waves can not be stopped anymore by dispersion and/or dissipation and becomes non-stationary

21. Appeal to experimental data of multi-point measurements: ClusterWhat are the right questions to answer making use of the data? • Does the front steepen with the growth of the Mach number till the scales comparable with electron inertial length? • What are the characteristic scales of fine structure of the shock front? • What are the sources of waves observed upstream of the ramp? • Can we observe direct manifestations of the overturning and reformation?

22. The answer can be found analysing scales and energy fluxes. What is the scale of the major transition? Is the region of strongest gradient determined by the dispersion – nonlinearity effects? Dispersive model: precursor and ramp transition are determined by dispersion-nonlinearity and scales as several c/ωpe (electron inertial length)

25. Magnetic field ramp thickness (Hobara et al, 2010)

26. Magnetic field ramp grasient (Hobara et al., 2010)

27. Magnetic ramp thickness statistics (Mazelle et al., 2010)

28. PRL, 2012

29. 2012 PRL, 2012

31. Electron heating (Schwartz et al., 2011)

32. Electron heating (Schwartz et al., 2011)

33. Electron heating (Schwartz et al., 2011)

34. Electric field on the interval 22:15:30-22:15:40

35. More details 22:15:33-22:15:34

36. Sundkvist et al., AGU 2012 • The heating can be super-adiabatic as well as sub-adiabatic • Parallel and perpendicular temperatures grow on the same time scale • The process is determined by the presence of the small scale electric field bursts

37. Small scale jumps of the electric field

38. Thank you for your attention • More details on seminar in September