التفاصيل البيبلوغرافية
| العنوان: |
Electromagnetic gyrokinetic PIC simulation with an adjustable control variates method |
| المؤلفون: |
Hatzky, R.1 roman.hatzky@rzg.mpg.de, Könies, A.2, Mishchenko, A.2 |
| المصدر: |
Journal of Computational Physics. Jul2007, Vol. 225 Issue 1, p568-590. 23p. |
| مصطلحات موضوعية: |
*FLUID mechanics, *CONTINUUM mechanics, *MONTE Carlo method, *NOISE |
| مستخلص: |
Abstract: In the last decade, it became clear that electromagnetic (gyro)kinetic particle-in-cell (PIC) simulations are very demanding in respect to numerical methods and the number of markers used. The Monte Carlo discretization of the gyrokinetic equations leads to a severe signal-to-noise problem: the statistical representation of the physically irrelevant but numerically dominant adiabatic current causing a high statistical noise level. The corresponding inaccuracy problem is very pronounced at high plasma β and/or small perpendicular wave numbers k ⊥. We derive several numerical schemes to overcome the problem using an adjustable control variates method which adapts to the dominant adiabatic part of the gyro-center distribution function. We have found that the inaccuracy problem is also present in the quasi-neutrality equation as a consequence of the p ∥-formulation [T.S. Hahm, W.W. Lee, A. Brizard, Nonlinear gyrokinetic theory for finite-beta plasmas, Phys. Fluids 31 (1988) 1940]. For slab simulations in the magnetohydrodynamic (MHD) limit , the number of markers can be reduced by more than four orders of magnitude compared to a conventional δf scheme. The derived schemes represent first steps on a road to fully adaptive control variates method which can significantly reduce the inherent statistical noise of PIC codes. [Copyright &y& Elsevier] |
| قاعدة البيانات: |
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