Improper resetting of pandf during jacobian calculation

[jguterl]

There are two variables in pandf subroutine which are not reinitalized between each call:

• the variable resmo in the following block for neutral species (zi(ifld)=0). I suggest to add an "else" statement to set resmo to zero when zi=0 (see cJG:suggested correction). The residual of the momentum for the gas species is thus wrong when nusp>1 which is the case when nhsp>1.

    do 99 iy = j2, j5
       do 98 ix = i2, i5
          ix2 = ixp1(ix,iy)
          if (zi(ifld) .ne. 0) then  # additions only for charged ions
             dp1 =  cngmom(ifld)*(1/fac2sp)*
                      ( ng(ix2,iy,1)*tg(ix2,iy,1)-
                        ng(ix ,iy,1)*tg(ix ,iy,1) )
             resmo(ix,iy,ifld) = 0.
             resmo(ix,iy,ifld) =
                  smoc(ix,iy,ifld)
                + smov(ix,iy,ifld) * up(ix,iy,ifld)
                - cfneut * cfneutsor_mi * sx(ix,iy) * rrv(ix,iy) * dp1
                - cfneut * cfneutsor_mi * cmwall(ifld)*0.5*(ng(ix,iy,1)+ng(ix2,iy,1))
                      * mi(ifld)*up(ix,iy,ifld)*0.5
                      *(nucx(ix,iy,1)+nucx(ix2,iy,1))*volv(ix,iy)
                + cmneut * cmneutsor_mi * uesor_up(ix,iy,ifld)
                + cfmsor*(msor(ix,iy,ifld) + msorxr(ix,iy,ifld)) #### IJ 2017: needs *cfneut for multi-charge state ions & MC neutrals?
                + volmsor(ix,iy,ifld)
                + cfvisxneov*visvol_v(ix,iy,ifld)
                + cfvisxneoq*visvol_q(ix,iy,ifld)
  c  Add drag with cold, stationary impurity neutrals
             if (ifld > nhsp) then
               resmo(ix,iy,ifld) = resmo(ix,iy,ifld) - cfupimpg*
                    0.25*mi(ifld)*(ni(ix,iy,ifld)+ni(ix2,iy,ifld))*
                     ( nucxi(ix,iy,ifld)+nucxi(ix2,iy,ifld)+
                      nueli(ix,iy,ifld)+nueli(ix2,iy,ifld) )*
                       up(ix,iy,ifld)*volv(ix,iy)
              endif
   cJG: suggest correction
          else
             resmo(ix,iy,ifld) = 0
          endif
  

• the electron power background variable pwrebkg is not reset properly when xinc!=0 or yinc!=0. That should not be a problem though as it is to prevent small values of pwrebkg. But that should be fixed for the pupose of code validation.