The interaction of turbulence with parallel and perpendicular shocks

15th Annual International Astrophysics Conference: "The Science of Ed Stone: Celebrating his 80th Birthday"

物理学;天文学

Adhikari, L.^1,2 ; Zank, G.P.^1,2 ; Hunana, P.^1,2 ; Hu, Q.^1,2

Department of Space Science, University of Alabama in Huntsville, Huntsville

AL

35899, United States^1

Center for Space Plasma and Aeronomic Research (CSPAR), University of Alabama in Huntsville, Huntsville

AL

35899, United States^2

关键词: Hyperbolic tangent function;    Interplanetary shocks;    Least square methods;    Magnetic and kinetic energies;    Rankine-Hugoniot condition;    Spacecraft observations;    Turbulence transports;    Turbulent fluctuation;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/767/1/012001/pdf
DOI  :  10.1088/1742-6596/767/1/012001

学科分类：天文学(综合)

来源: IOP

【 摘 要 】

Interplanetary shocks exist in most astrophysical flows, and modify the properties of the background flow. We apply the Zank et al 2012 six coupled turbulence transport model equations to study the interaction of turbulence with parallel and perpendicular shock waves in the solar wind. We model the 1D structure of a stationary perpendicular or parallel shock wave using a hyperbolic tangent function and the Rankine-Hugoniot conditions. A reduced turbulence transport model (the 4-equation model) is applied to parallel and perpendicular shock waves, and solved using a 4th- order Runge Kutta method. We compare the model results with ACE spacecraft observations. We identify one quasi-parallel and one quasi-perpendicular event in the ACE spacecraft data sets, and compute various turbulent observed values such as the fluctuating magnetic and kinetic energy, the energy in forward and backward propagating modes, the total turbulent energy in the upstream and downstream of the shock. We also calculate the error associated with each turbulent observed value, and fit the observed values by a least square method and use a Fourier series fitting function. We find that the theoretical results are in reasonable agreement with observations. The energy in turbulent fluctuations is enhanced and the correlation length is approximately constant at the shock. Similarly, the normalized cross helicity increases across a perpendicular shock, and decreases across a parallel shock.