private subroutine init_wdrift()
allocate wdriftx_phi, the factor multiplying dphi/dx in the magnetic drift term
allocate wdrifty_phi, the factor multiplying dphi/dy in the magnetic drift term
allocate wdriftx_bpar, the factor multiplying dbpar/dx in the magnetic drift term
allocate wdrifty_bpar, the factor multiplying dbpar/dy in the magnetic drift term
allocate wdriftx_g, the factor multiplying dg/dx in the magnetic drift term
allocate wdrifty_g, the factor multiplying dg/dy in the magnetic drift term
this is the curvature drift piece of wdrifty with missing factor of vpa
vpa factor is missing to avoid singularity when including
non-Maxwellian corrections to equilibrium
this is the grad-B drift piece of wdrifty
if including neoclassical correction to equilibrium Maxwellian,
then add in v_E^{nc} . grad y dg/dy coefficient here
if maxwwellian_normalization = .true., evolved distribution function is normalised by a Maxwellian
otherwise, it is not; a Maxwellian weighting factor must thus be included
assign wdrifty_bpar, neoclassical terms not supported
if including neoclassical corrections to equilibrium,
add in -(Ze/m) * v_curv/vpa . grad y d/dy * dF^{nc}/dvpa term
and v_E . grad z dF^{nc}/dz (here get the dphi/dy part of v_E)
NB: the below neoclassical correction needs to be divided by an equilibrium Maxwellian
if maxwellian_normalization = .true.
this is the curvature drift piece of wdriftx with missing factor of vpa
vpa factor is missing to avoid singularity when including
non-Maxwellian corrections to equilibrium
this is the grad-B drift piece of wdriftx
if including neoclassical correction to equilibrium Maxwellian,
then add in v_E^{nc} . grad x dg/dx coefficient here
if maxwellian_normalizatiion = .true., evolved distribution function is normalised by a Maxwellian
otherwise, it is not; a Maxwellian weighting factor must thus be included
assign wdriftx_bpar, neoclassical terms not supported
if including neoclassical corrections to equilibrium,
add in (Ze/m) * v_curv/vpa . grad x d/dx * dF^{nc}/dvpa term
and v_E . grad z dF^{nc}/dz (here get the dphi/dx part of v_E)
and v_E . grad alpha dF^{nc}/dalpha (dphi/dx part of v_E)
NB: the below neoclassical correction needs to be divided by an equilibrium Maxwellian
if running with maxwellian_normalzation = .true.
Arguments
None