کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
10694475 | 1020120 | 2011 | 18 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Velocity correlation functions of charged particles derived from the Fokker-Planck equation
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
علوم زمین و سیارات
علوم فضا و نجوم
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چکیده انگلیسی
An important ingredient in theories for diffusion of charged particles across a mean magnetic field are velocity correlation functions along and across that field. In the current article we present an analytical study of these functions by investigating the two-dimensional Fokker-Planck equation. We show that for an isotropic pitch-angle Fokker-Planck coefficient, the parallel velocity correlation function is an exponential function in agreement with the standard model used previously. For other forms of the pitch-angle diffusion coefficient, however, we find non-exponential forms. Also a new, velocity correlation function based, approach for deriving the so-called Earl-relation is presented. This new derivation is more systematic and simpler than previous derivations. We also discuss higher-order velocity correlations and the applicability of the quasi-normal hypothesis in particle diffusion theory. Furthermore, we compute velocity correlation functions across the mean field and develop an alternative theory for perpendicular diffusion.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Advances in Space Research - Volume 47, Issue 7, 1 April 2011, Pages 1147-1164
Journal: Advances in Space Research - Volume 47, Issue 7, 1 April 2011, Pages 1147-1164
نویسندگان
A. Shalchi,