Study of momentum diffusion with the effect of adiabatic focusing

Discussion timeslot (ZOOM-Meeting): 16. July 2021 - 18:00
ZOOM-Meeting URL: https://icrc2021.desy.de/pf_access_abstracts
Corresponding Session: https://icrc2021-venue.desy.de/channel/Presenter-Forum-1-Evening-All-Categories/48
Abstract:
'Momentum diffusion of the energetic charged particles is an important mechanism of therntransport process in astrophysics, physics of the fusion devices, and laboratory plasmas. rnIn the light of observations, for the investigation of energetic particlerntransport through magnetized plasma, one usually assumes thernmagnetic field configuration as the superposition of the backgroundrnmagnetic field $B_0$ and the turbulent component $delta B$. rnThe fact that large-scale magnetic field is nonuniform in spacerngives rise to the so called adiabatic focusing effectrnof the energetic particles. rnPrevious authors found that the along-field focuing rncan lead to the convective term in momentum space. rnHere, we explore the momentum diffusion depending on the adiabatic focusing rneffect along the background magnetic field. rnBy employing the iteration method, rnwe derive the momentum diffusion coefficient $A(xi)=A_0+mathcal{M}_4(xi)$ rnwith the uniform field momentum diffusion coefficient $A_0$ and rnthe modifying term $mathcal{M}_4(xi)=M_1(xi)+M_2(xi)+M_3(xi)+M_4(xi)$ rnby retaining up to the fourth order of the focusing parameter $xi$. rnThereafter, we evaluate the modifying term $mathcal{M}_4(xi)$rnto find that it is not equal to zero for most of the cases, so that we obtain rna new second order acceleration mechanism of energetic charged particles.rnAfter evaluating the modifying term, rnwe find that it is determined by rnthe sign of the focusing characteristic length rnand the cross helicity of turbulent magnetic field.'

Authors: junfang wang | Gang Qin
Indico-ID: 950
Proceeding URL: https://pos.sissa.it/395/1352