!
      subroutine dynamics(nstep,istep)
!
! Call dynamics layer of the model for current time step.
! Routines that do not have to do message-passing are generally called
!   from inside a latitude scan in this routine. Routines that do have
!   to make mpi calls are called once from this routine, and latitude
!   scan(s) are inside the called routine.
!
! Include the option of setting the lower boundary by using GSWM output
! this affects subroutine dt and duv
!
! am 6/06: change call to qjoule_ti to include ion and neutral density
!          factors, include vertical component
!          change call to qjoule_tn to include vertical velocity
! btf 12/6/05: 
!   Converted addfsech calls to addfld (called only when diags==.true.)
!
! 1/27/06 btf: call gwsource for zp-10 lbc (see mgw.F).
!
      use fields_module
      use mpi_module,only: lon0,lon1,lat0,lat1,mytidi
#ifdef MPI
      use mpi_module,only: distribute_1d,mp_close
#endif
      use bndry_module,only: bndcmp
      use chemrates_module,only: chemrates_tdep
      use qrj_module,only: qrj,qtotal,qop,qo2p,qn2p,qnp,qnop
      use chapman_module,only: chapman
      use oplus_module,only: oplus
      use input_module,only: iaurora=>aurora,nstepqrj,gswm_rayfric,
     |  solgar_eddy=>sgar_eddy
      use aurora_module,only: aurora
      use n4s_module,only: comp_n4s,minor_n4s
      use no_module,only: comp_no,minor_no
      use hdif_module,only: hdif3,hdif_bndlons,hdif_periodic
      use timing_module,only: timer,timing
      use advance_module,only: time2print
      use addfld_module,only: addfld
      use tuv_bndry,only: tuvbnd
      use mgw,only: gwsource
      use radcool_module,only: radcool
      use init_module,only: iyear,secs
      use hist_module,only: modeltime
      use gswm_mlt,only: gswm2gcm,sgar2gcm
!
      implicit none
!
! Args:
      integer,intent(in) :: nstep,istep
!
! VT vampir tracing:
!
#ifdef VT
#include <VT.inc>
#endif
!
! Local:
      integer :: i,j,k,n,lat,ier
      integer :: i0,i1,nk,nkm1,nlats,k0,k1
      logical,parameter :: debug=.false. ! add prints to stdout
!
! If diags is set true, the following fields will be written to
! secondary histories:
!
! SECFLDS = 'CP','KT','KM','W_OMEGA','UI_ExB','VI_ExB','WI_ExB',
!           'SCO2','SCO1','SCN2','QTOTAL','QOP','QO2P','QN2P','QNP',
!           'QNOP','OPLUS','XIOP2P','XIOP2D','NP_diag','N2P_diag',
!           'NOP_diag','O2P_diag','ELDEN','LXX','LYY','LXY','LYX',
!           'LAM1','SIGMAPED','SIGMAHAL','CMP_N4S','CMP_NO','QJI_TI',
!           'T_ELEC','T_ION','COOL_IMPLICIT','COOL_EXPLICIT',
!           'QJI_TN','TN_UPD','UN_UPD','VN_UPD','O2_UPD','O1_UPD'
!
      logical,parameter :: diags=.false. ! put fields on sec hist
      real :: time0,time1,time1_qrj,time1_cmpminor,time1_cmpmajor
!
      if (debug) write(6,"(/,'Enter dynamics.')")
      i0=lon0 ; i1=lon1 ; nk=nlevp1 ; nkm1=nk-1 ! for addfsech
      k0=1 ; k1=nlevp1
      nlats = lat1-lat0+1
!
      call bndcmp
      if (debug) write(6,"('dynamics after bndcmp')")
!
! Calculate specific heat and molecular viscosity.
! f4d itp fields are input, f3d fields are output.
!
      do lat=lat0,lat1
        call cpktkm(
     |    tn(levd0,lond0,lat,itp), ! 4d input
     |    o2(levd0,lond0,lat,itp), ! 4d input
     |    o1(levd0,lond0,lat,itp), ! 4d input
     |    cp(levd0,lond0,lat),     ! 3d output
     |    kt(levd0,lond0,lat),     ! 3d output
     |    km(levd0,lond0,lat),     ! 3d output
     |    1,nlevp1,lon0,lon1,lat)
      enddo ! lat=lat0,lat1
      if (debug) write(6,"('dynamics after cpktkm')")
      if (diags) then
        do lat=lat0,lat1
          call addfld('CP','CP',' ',cp(:,i0:i1,lat),
     |      'lev',k0,k1,'lon',i0,i1,lat)
          call addfld('KT','KT',' ',kt(:,i0:i1,lat),
     |      'lev',k0,k1,'lon',i0,i1,lat)
          call addfld('KM','KM',' ',km(:,i0:i1,lat),
     |      'lev',k0,k1,'lon',i0,i1,lat)
        enddo
      endif
!
! Calculate omega for vertical velocity:
! (latitude scan is inside swdot)
!
      if (debug) write(6,"('dynamics before swdot')")
      call swdot(
     |  un(levd0,lond0,latd0,itp), ! un input
     |  vc(levd0,lond0,latd0,itp), ! vc input
     |  w (levd0,lond0,latd0,itc), ! omega output
     |  1,nlevp1,lon0,lon1,lat0,lat1,lat0,lat1)
      if (debug) write(6,"('dynamics after swdot')")
      if (diags) then
        do lat=lat0,lat1
          call addfld('W_OMEGA','VERTICAL MOTION (DZp/DT)',
     |    's-1',w(:,i0:i1,lat,itc),'lev',k0,k1,'lon',i0,i1,lat)
        enddo
      endif
!
! Calculate ExB ion drift velocities from electric field:
!
      call ionvel(
     |  z (levd0,lond0,latd0,itc), ! geopotential input
     |  ui(levd0,lond0,latd0),     ! U ion velocity output
     |  vi(levd0,lond0,latd0),     ! V ion velocity output
     |  wi(levd0,lond0,latd0),     ! W ion velocity output
     |  1,nlevp1,lon0,lon1,lat0,lat1)
      if (debug) write(6,"('dynamics after ionvel')")
      if (diags) then
        do lat=lat0,lat1
          call addfld('UI_ExB','Zonal ExB Ion Drift','cm/s',
     |      ui(:,i0:i1,lat),'lev',k0,k1,'lon',i0,i1,lat)
          call addfld('VI_ExB','Meridional ExB Ion Drift','cm/s',
     |      vi(:,i0:i1,lat),'lev',k0,k1,'lon',i0,i1,lat)
          call addfld('WI_ExB','Vertical ExB Ion Drift','cm/s',
     |      wi(:,i0:i1,lat),'lev',k0,k1,'lon',i0,i1,lat)
        enddo
      endif
!
! Calculate column densities and line integrals of o2, o, and n2.
! Prognostics z,tn,o2,o1,barm are input, diagnostics vo2,vo1,vn2,
!   sco2,sco1,scn2 are output.
!
      do lat=lat0,lat1
        call chapman(
     |    z   (levd0,lond0,lat,itc), ! updated Z from addiag
     |    tn  (levd0,lond0,lat,itp), ! 4d in
     |    o2  (levd0,lond0,lat,itp), ! 4d in
     |    o1  (levd0,lond0,lat,itp), ! 4d in
     |    barm(levd0,lond0,lat,itp), ! 4d in
     |    vo2 (levd0,lond0,lat),     ! 3d out
     |    vo1 (levd0,lond0,lat),     ! 3d out
     |    vn2 (levd0,lond0,lat),     ! 3d out
     |    sco2(levd0,lond0,lat),     ! 3d out
     |    sco1(levd0,lond0,lat),     ! 3d out
     |    scn2(levd0,lond0,lat),     ! 3d out
     |    1,nlevp1,lon0,lon1,lat)
      enddo ! lat=lat0,lat1
      if (debug) write(6,"('dynamics after chapman')")
      if (diags) then
!
! Post-processors cannot read 1.e80, so change these to
! 1.e36 if saving on secondary histories (then change back
! for rest of model):
        do lat=lat0,lat1
          do k=k0,k1
            do i=i0,i1
              if (sco2(k,i,lat)==1.e80) sco2(k,i,lat)=1.e36
              if (sco1(k,i,lat)==1.e80) sco1(k,i,lat)=1.e36
              if (scn2(k,i,lat)==1.e80) scn2(k,i,lat)=1.e36
            enddo
          enddo
          call addfld('SCO2','Chapman slant-column O2',' ',
     |      sco2(:,i0:i1,lat),'lev',k0,k1,'lon',i0,i1,lat)
          call addfld('SCO1','Chapman slant-column O1',' ',
     |      sco1(:,i0:i1,lat),'lev',k0,k1,'lon',i0,i1,lat)
          call addfld('SCN2','Chapman slant-column N2',' ',
     |      scn2(:,i0:i1,lat),'lev',k0,k1,'lon',i0,i1,lat)
          do k=k0,k1
            do i=i0,i1
              if (sco2(k,i,lat)==1.e36) sco2(k,i,lat)=1.e80
              if (sco1(k,i,lat)==1.e36) sco1(k,i,lat)=1.e80
              if (scn2(k,i,lat)==1.e36) scn2(k,i,lat)=1.e80
            enddo
          enddo
        enddo
      endif
!
! Calculate temperature dependent reaction rates (chemrates_module): 
!
      do lat=lat0,lat1
        call chemrates_tdep(
     |    tn  (levd0,lond0,lat,itp),
     |    te  (levd0,lond0,lat,itp),
     |    ti  (levd0,lond0,lat,itp),
     |    sco2(levd0,lond0,lat),
     |    vo2 (levd0,lond0,lat),
     |    1,nlevp1,lon0,lon1,lat)
      enddo
      if (debug) write(6,"('dynamics after chemrates_tdep')")
!
! Latitude scan for qrj, qinite, and aurora.
!
#ifdef VT
!     code = 122 ; state = 'ions' ; activity='ModelCode'
      call vtbegin(122,ier)
#endif
      time1_qrj = 0.
      do lat=lat0,lat1
!
! Calculate ionization and heating rates:
!
        if (mod(istep,nstepqrj)==0) then
          if (debug) write(6,"('dynamics call qrj: lat=',i3)") lat
          call timer(time0,time1,'QRJ',0,0) ! start qrj timing for current lat
          call qrj(
     |      sco2(levd0,lond0,lat),
     |      sco1(levd0,lond0,lat),
     |      scn2(levd0,lond0,lat),
!    |      sco3(levd0,lond0,lat),
     |      tn  (levd0,lond0,lat,itp),
     |      no  (levd0,lond0,lat,itp),
     |      o2  (levd0,lond0,lat,itp),
     |      o1  (levd0,lond0,lat,itp),
!    |      o3  (levd0,lond0,lat,itp),
     |      n4s (levd0,lond0,lat,itp),
     |      xnmbari(levd0,lond0,lat),
     |      1,nlevp1,lon0,lon1,lat)
          call timer(time0,time1,'QRJ',1,0) ! end qrj timing for current lat
          time1_qrj = time1_qrj+time1
          if (debug) write(6,"('dynamics after qrj: lat=',i3)") lat
        endif ! time to call qrj
!       if (diags) then
          call addfld('QTOTAL','Total Heating',' ',
     |      qtotal(:,i0:i1,lat),'lev',k0,k1,'lon',i0,i1,lat)
          call addfld('QOP'   ,'QO+ from QRJ',' ',
     |      qop(:,i0:i1,lat),'lev',k0,k1,'lon',i0,i1,lat)
          call addfld('QO2P'  ,'QO2+ from QRJ',' ',
     |      qo2p(:,i0:i1,lat),'lev',k0,k1,'lon',i0,i1,lat)
          call addfld('QN2P'  ,'QN2+ from QRJ',' ',
     |      qn2p(:,i0:i1,lat),'lev',k0,k1,'lon',i0,i1,lat)
          call addfld('QNP'   ,'QN+ from QRJ',' ',
     |      qnp(:,i0:i1,lat),'lev',k0,k1,'lon',i0,i1,lat)
          call addfld('QNOP'  ,'QNO+ from QRJ',' ',
     |      qnop(:,i0:i1,lat),'lev',k0,k1,'lon',i0,i1,lat)
!       endif
!
! Calculate background (nightime) ionization:
        call qinite(
     |    o2     (levd0,lond0,lat,itp),
     |    o1     (levd0,lond0,lat,itp),
     |    no     (levd0,lond0,lat,itp),
     |    xnmbari(levd0,lond0,lat),
     |    vo2    (levd0,lond0,lat),
     |    vo1    (levd0,lond0,lat),
     |    vn2    (levd0,lond0,lat),
     |    1,nlevp1,lon0,lon1,lat)
        if (debug) write(6,"('dynamics after qinite: lat=',i3)") lat
!
! Add aurora particle precip and ionization:
        if (iaurora > 0) then
          call aurora(
     |      tn  (levd0,lond0,lat,itp),
     |      o2  (levd0,lond0,lat,itp),
     |      o1  (levd0,lond0,lat,itp),
     |      barm(levd0,lond0,lat,itp),
     |      1,nlevp1,lon0,lon1,lat)
          if (debug) write(6,"('dynamics after aurora: lat=',i3)") lat
        endif
      enddo ! lat=lat0,lat1 for qrj, qinite, and aurora
      if (debug) write(6,"('dynamics after qrj,qinite,aurora')")
!
! Report timing from above latitude loop:
      if (timing%level >= 2.and.time2print(nstep,istep))
     |  write(6,"('Time in QRJ =          ',
     |    f12.2,' Dynamics: step ',i5)") time1_qrj,istep
!
#ifdef VT
!     code = 122 ; state = 'ions' ; activity='ModelCode'
      call vtend(122,ier)
#endif
!
! Advance O+:
! Oplus makes several calls to mp_bndlons_f3d, mp_periodic_f3d,
!   mp_gatherlons_f3d, and mp_scatterlons_f3.
! Full task subdomains (including ghost cells) are passed.
!
      call timer(time0,time1,'OPLUS',0,0) ! start oplus timing
      call oplus(
     |  tn    (levd0,lond0,latd0,itp),
     |  te    (levd0,lond0,latd0,itp),
     |  ti    (levd0,lond0,latd0,itp),
     |  o2    (levd0,lond0,latd0,itp),
     |  o1    (levd0,lond0,latd0,itp),
     |  n2d   (levd0,lond0,latd0,itp),
     |  ne    (levd0,lond0,latd0,itp),
     |  un    (levd0,lond0,latd0,itp),
     |  vn    (levd0,lond0,latd0,itp),
     |  w     (levd0,lond0,latd0,itp),
     |  barm  (levd0,lond0,latd0,itp),
     |  ui    ,
     |  vi    ,
     |  wi    ,
     |  xnmbar,
     |  op    (levd0,lond0,latd0,itp),
     |  op_nm (levd0,lond0,latd0,itp),
     |  op    (levd0,lond0,latd0,itc), ! out
     |  op_nm (levd0,lond0,latd0,itc), ! out
     |  xiop2p,                        ! out
     |  xiop2d,                        ! out
     |  1,nlevp1,lon0,lon1,lat0,lat1)
      if (debug) write(6,"('dynamics after oplus')")
      call timer(time0,time1,'OPLUS',1,0) ! end oplus timing
      if (timing%level >= 2.and.time2print(nstep,istep))
     |  write(6,"('Time in OPLUS =        ',
     |    f12.2,' Dynamics: step ',i5)") time1,istep
      if (diags) then
        do lat=lat0,lat1
          call addfld('OPLUS' ,'O+ Ion',' ',op(:,i0:i1,lat,itc),
     |      'lev',k0,k1,'lon',i0,i1,lat)
          call addfld('XIOP2P','O+(2P)',' ',xiop2p(:,i0:i1,lat),
     |      'lev',k0,k1,'lon',i0,i1,lat)
          call addfld('XIOP2D','O+(2D)',' ',xiop2d(:,i0:i1,lat),
     |      'lev',k0,k1,'lon',i0,i1,lat)
        enddo
      endif
!
! Electron density:
!
      do lat=lat0,lat1
        call elden(
     |    tn    (levd0,lond0,lat,itp),
     |    barm  (levd0,lond0,lat,itp),
     |    op    (levd0,lond0,lat,itp), ! O+ at current time step
     |    op    (levd0,lond0,lat,itc), ! O+ updated by sub oplus
     |    o2    (levd0,lond0,lat,itp),
     |    o1    (levd0,lond0,lat,itp),
     |    n2d   (levd0,lond0,lat,itp),
     |    no    (levd0,lond0,lat,itp),
     |    n4s   (levd0,lond0,lat,itp),
     |    xiop2p(levd0,lond0,lat),      ! from oplus
     |    xiop2d(levd0,lond0,lat),      ! from oplus
     |    nplus (levd0,lond0,lat),      ! N+  output
     |    n2p   (levd0,lond0,lat),      ! N2+ output
     |    nop   (levd0,lond0,lat),      ! NO+ output
     |    o2p   (levd0,lond0,lat,itc),  ! O2+ output
     |    ne    (levd0,lond0,lat,itc),  ! electron density output
     |    1,nlevp1,lon0,lon1,lat)
      enddo ! lat=lat0,lat1
      if (debug) write(6,"('dynamics after oplus')")
!
! Ions and electron density are at interface levels (ilev):
      do lat=lat0,lat1
        if (diags) then
          call addfld('NP_diag' ,'N+ Ion' ,'cm^3',nplus(:,i0:i1,lat),
     |      'ilev',k0,k1,'lon',i0,i1,lat)
          call addfld('N2P_diag','N2+ Ion','cm^3',n2p(:,i0:i1,lat),
     |      'ilev',k0,k1,'lon',i0,i1,lat)
          call addfld('NOP_diag','NO+ Ion','cm^3',nop(:,i0:i1,lat),
     |      'ilev',k0,k1,'lon',i0,i1,lat)
          call addfld('O2P_diag','O2+ Ion','cm^3',o2p(:,i0:i1,lat,itc),
     |      'ilev',k0,k1,'lon',i0,i1,lat)
          call addfld('ELDEN' ,'Electron Density','cm-3',
     |      ne (:,i0:i1,lat,itc),'ilev',k0,k1,'lon',i0,i1,lat)
        endif
      enddo ! lat=lat0,lat1
!
! Get gswm rayleigh friction and sol-gar eddy diffusion (see gswm_mlt.F):
! Note sgar_eddy is converted from m^2/s to s-1 in gwsource for comp.
! (sgar_eddy can also be saved as diagnostic in m/s/day in gwsource)
!
      if (solgar_eddy > 0) then
        call sgar2gcm(modeltime,iyear,
     |    z   (levd0,lond0,latd0,itp),   ! input
     |    sgar_eddy(levd0,lond0,latd0),  ! output eddy diffusion
     |    1,nlevp1,lon0,lon1,lat0,lat1)
!       do lat=lat0,lat1
!         call addfld('SGAR_EDDY','SGAR eddy diffusion from gswm_mlt',
!    |      'm^2/s',sgar_eddy(:,i0:i1,lat),'lev',k0,k1,'lon',i0,i1,lat)
!       enddo
      endif
!
      if (gswm_rayfric > 0) then
        call gswm2gcm(modeltime,iyear,
     |    z(levd0,lond0,latd0,itc),      ! input
     |    tn  (levd0,lond0,latd0,itp),   ! input
     |    barm(levd0,lond0,latd0,itp),   ! input
     |    gswm_rfu(levd0,lond0,latd0),   ! output U rayleigh friction
     |    gswm_rfv(levd0,lond0,latd0),   ! output V rayleigh friction
     |    1,nlevp1,lon0,lon1,lat0,lat1)
!
!       do lat=lat0,lat1
!         call addfld('GSWM_U_RAYFRIC','GSWM U Rayleigh friction','s-1',
!    |      gswm_rfu(:,i0:i1,lat),'lev',k0,k1,'lon',i0,i1,lat)
!         call addfld('GSWM_V_RAYFRIC','GSWM V Rayleigh friction','s-1',
!    |      gswm_rfv(:,i0:i1,lat),'lev',k0,k1,'lon',i0,i1,lat)
!       enddo
      endif
!
! Lamda ion drag coefficients:
!
      time1_cmpminor = 0.
      do lat=lat0,lat1
        call lamdas(
     |    tn  (levd0,lond0,lat,itp),
     |    barm(levd0,lond0,lat,itp),
     |    o2  (levd0,lond0,lat,itp),
     |    o1  (levd0,lond0,lat,itp),
     |    ti  (levd0,lond0,lat,itp),
     |    te  (levd0,lond0,lat,itp),
     |    o2p (levd0,lond0,lat,itp),
     |    op  (levd0,lond0,lat,itp),
     |    nop (levd0,lond0,lat),
     |    lxx (levd0,lond0,lat), ! LXX output
     |    lyy (levd0,lond0,lat), ! LYY output
     |    lxy (levd0,lond0,lat), ! LXY output
     |    lyx (levd0,lond0,lat), ! LYX output
     |    lam1(levd0,lond0,lat), ! LAM1 output
     |    ped (levd0,lond0,lat), ! pedersen conductivity output
     |    hall(levd0,lond0,lat), ! hall conductivity output
     |    1,nlevp1,lon0,lon1,lat)
        if (debug) write(6,"('dynamics after lamdas: lat=',i3)") lat
        if (diags) then
          call addfld('LXX','Lamda XX',' ',lxx(:,i0:i1,lat),
     |      'lev',k0,k1,'lon',i0,i1,lat)
          call addfld('LYY','Lamda YY',' ',lyy(:,i0:i1,lat),
     |      'lev',k0,k1,'lon',i0,i1,lat)
          call addfld('LXY','Lamda XY',' ',lxy(:,i0:i1,lat),
     |      'lev',k0,k1,'lon',i0,i1,lat)
          call addfld('LYX','Lamda YX',' ',lyx(:,i0:i1,lat),
     |      'lev',k0,k1,'lon',i0,i1,lat)
          call addfld('LAM1','LAM1','1/s',lam1(:,i0:i1,lat),
     |      'lev',k0,k1,'lon',i0,i1,lat)
          call addfld('SIGMAPED','Pedersen Conductivity','S/m',
     |      ped(:,i0:i1,lat),'lev',k0,k1,'lon',i0,i1,lat)
          call addfld('SIGMAHAL','Hall Conductivity','S/m',
     |      hall(:,i0:i1,lat),'lev',k0,k1,'lon',i0,i1,lat)
        endif
!
! Define mgw terms raykk, etc:
        call gwsource(
     |    tn  (levd0,lond0,lat,itp),  ! input
     |    barm(levd0,lond0,lat,itp),  ! input
     |    gswm_rfu (levd0,lond0,lat), ! rayleigh fric from gswm2gcm
     |    gswm_rfv (levd0,lond0,lat), ! rayleigh fric from gswm2gcm
     |    sgar_eddy(levd0,lond0,lat), ! eddy diff from sgar2gcm
     |    levd0,levd1,lon0,lon1,lat)
!
! Calculate n2d:
        call timer(time0,time1,'CMPMINOR',0,0) ! start comp minor timing
        call comp_n2d(
     |    o2  (levd0,lond0,lat,itp),
     |    o1  (levd0,lond0,lat,itp),
     |    no  (levd0,lond0,lat,itp),
     |    n4s (levd0,lond0,lat,itp),
     |    ne  (levd0,lond0,lat,itp),
     |    op  (levd0,lond0,lat,itp),
     |    n2p (levd0,lond0,lat),
     |    nop (levd0,lond0,lat),
     |    sco2(levd0,lond0,lat),
     |    xnmbarm(levd0,lond0,lat),
     |    n2d (levd0,lond0,lat,itc), ! N2D output
     |    1,nlevp1,lon0,lon1,lat)
        if (debug) write(6,"('dynamics after comp_n2d: lat=',i3)") lat
      enddo ! lat=lat0,lat1
      call timer(time0,time1,'CMPMINOR',1,0) ! suspend comp minor timing
      time1_cmpminor = time1_cmpminor+time1
!     if (diags) then
!       call addfsech('CMP_N2D',' ',' ',n2d(:,i0:i1,lat,itc),
!    |    i0,i1,nk,nkm1,lat)
!     endif
!
! Advance n4s:
!
      call timer(time0,time1,'CMPMINOR',0,0) ! resume comp minor timing
      do lat=lat0,lat1
        call comp_n4s(
     |    tn     (levd0,lond0,lat,itp),  ! TN (deg K)
     |    o2     (levd0,lond0,lat,itp),  ! O2 (mmr)
     |    o1     (levd0,lond0,lat,itp),  ! O (mmr)
     |    barm   (levd0,lond0,lat,itp),  ! mean mol weight
     |    xnmbarm(levd0,lond0,lat),      ! p0*e(-z)*barm
     |    no     (levd0,lond0,lat,itp),  ! NO
     |    n2d    (levd0,lond0,lat,itc),  ! N(2D) from comp_n2d
     |    ne     (levd0,lond0,lat,itp),  ! Ne
     |    o2p    (levd0,lond0,lat,itp),  ! O2+
     |    op     (levd0,lond0,lat,itp),  ! O+
     |    n2p    (levd0,lond0,lat),      ! N2+ from elden
     |    nplus  (levd0,lond0,lat),      ! N+  from elden
     |    nop    (levd0,lond0,lat),      ! NO+ from elden
     |    1,nlevp1,lon0,lon1,lat)
      enddo ! lat=lat0,lat1 
      if (debug) write(6,"('dynamics after comp_n4s')")
!
! Minor_n4s calls sub minor, which has 3d mpi calls, including gather/scatter
! for fft filtering. Full 3d task subdomains are passed.
!
      call minor_n4s(
     |    tn     (levd0,lond0,latd0,itp),  ! TN (deg K)
     |    o2     (levd0,lond0,latd0,itp),  ! O2 (mmr)
     |    o1     (levd0,lond0,latd0,itp),  ! O (mmr)
     |    n4s    (levd0,lond0,latd0,itp),  ! n4s from previous step
     |    n4s_nm (levd0,lond0,latd0,itp),  ! n4s at time n-1
     |    n4s    (levd0,lond0,latd0,itc),  ! output n4s
     |    n4s_nm (levd0,lond0,latd0,itc),  ! output n4s at time n-1
     |    1,nlevp1,lon0,lon1,lat0,lat1)
      if (debug) write(6,"('dynamics after minor_n4s')")
      call timer(time0,time1,'CMPMINOR',1,0) ! suspend comp minor timing
      time1_cmpminor = time1_cmpminor+time1
      if (diags) then
        do lat=lat0,lat1
          call addfld('CMP_N4S','N4S density','mmr',
     |      n4s(:,i0:i1,lat,itc),'lev',k0,k1,'lon',i0,i1,lat)
        enddo
      endif
! 
! Advance NO: 
!
      call timer(time0,time1,'CMPMINOR',0,0) ! resume comp minor timing
      do lat=lat0,lat1
        call comp_no(
     |    tn     (levd0,lond0,lat,itp),
     |    o2     (levd0,lond0,lat,itp),
     |    o1     (levd0,lond0,lat,itp),
     |    barm   (levd0,lond0,lat,itp),
     |    xnmbarm(levd0,lond0,lat),
     |    n4s    (levd0,lond0,lat,itp),
     |    n2d    (levd0,lond0,lat,itc),
     |    ne     (levd0,lond0,lat,itp),
     |    o2p    (levd0,lond0,lat,itp),
     |    1,nlevp1,lon0,lon1,lat)
      enddo ! lat=lat0,lat1 
      if (debug) write(6,"('dynamics after comp_no')")
!
! Minor_no calls minor, which has 3d mpi calls:
      call minor_no(
     |    tn   (levd0,lond0,latd0,itp),  ! TN (deg K)
     |    o2   (levd0,lond0,latd0,itp),  ! O2 (mmr)
     |    o1   (levd0,lond0,latd0,itp),  ! O (mmr)
     |    no   (levd0,lond0,latd0,itp),  ! current no
     |    no_nm(levd0,lond0,latd0,itp),  ! no at time n-1
     |    no   (levd0,lond0,latd0,itc),  ! output no
     |    no_nm(levd0,lond0,latd0,itc),  ! output no at time n-1
     |    1,nlevp1,lon0,lon1,lat0,lat1)
      if (debug) write(6,"('dynamics after minor_no')")
      call timer(time0,time1,'CMPMINOR',1,0) ! suspend comp minor timing
      time1_cmpminor = time1_cmpminor+time1
      if (timing%level >= 2.and.time2print(nstep,istep))
     |  write(6,"('Time in CMPMINOR =     ',f12.2,
     |    ' Dynamics: step ',i5)") time1_cmpminor,istep
      if (diags) then
        do lat=lat0,lat1
          call addfld('CMP_NO','NO density','mmr',
     |      no(:,i0:i1,lat,itc),'lev',k0,k1,'lon',i0,i1,lat)
        enddo
      endif
!
! Calculate additions to neutral gas heating and O2 dissociation
! due to N, NO chemistry:
!
      do lat=lat0,lat1
        call qjnno(
     |    tn   (levd0,lond0,lat,itp),
     |    o2   (levd0,lond0,lat,itp),
     |    o1   (levd0,lond0,lat,itp),
     |    ne   (levd0,lond0,lat,itp),
     |    no   (levd0,lond0,lat,itp),
     |    n4s  (levd0,lond0,lat,itp),
     |    n2d  (levd0,lond0,lat,itc), ! from comp_n2d
     |    xnmbarm(levd0,lond0,lat),
     |    1,nlevp1,lon0,lon1,lat)
      enddo
      if (debug) write(6,"('dynamics after qjnno')")
!
! Calculate ion chemistry contribution to neutral gas heating
!   and O2 dissociation:
!
      do lat=lat0,lat1
        call qjion(
     |    tn    (levd0,lond0,lat,itp),
     |    o2    (levd0,lond0,lat,itp),
     |    o1    (levd0,lond0,lat,itp),
     |    o2p   (levd0,lond0,lat,itp),
     |    op    (levd0,lond0,lat,itp),
     |    n4s   (levd0,lond0,lat,itp),
     |    n2d   (levd0,lond0,lat,itp),
     |    no    (levd0,lond0,lat,itp),
     |    ne    (levd0,lond0,lat,itp),
     |    barm  (levd0,lond0,lat,itp),
     |    n2p   (levd0,lond0,lat),     ! from elden
     |    nplus (levd0,lond0,lat),     ! from elden
     |    nop   (levd0,lond0,lat),     ! from elden
     |    xiop2p(levd0,lond0,lat),     ! from oplus 
     |    xiop2d(levd0,lond0,lat),     ! from oplus
     |    1,nlevp1,lon0,lon1,lat)
      enddo ! lat=lat0,lat1
      if (debug) write(6,"('dynamics after qjion')")
!
! Electron and Ion temperatures:
!
      do lat=lat0,lat1
!
! Joule heating for ion temperature:
        call qjoule_ti(
     |    un (levd0,lond0,lat,itp), ! zonal neutral velocity input
     |    vn (levd0,lond0,lat,itp), ! meridional velocity input
     |    w  (levd0,lond0,lat,itp), ! vertical velocity input
     |    ui (levd0,lond0,lat),     ! zonal ion velocity input (ExB)
     |    vi (levd0,lond0,lat),     ! meridional ion velocity input (ExB)
     |    wi (levd0,lond0,lat),     ! vertical ion velocity input (ExB)
     |    lam1(levd0,lond0,lat),    ! lambda_1 ion drag coefficient [1/s]
     |    op (levd0,lond0,lat,itp), ! O+ 1/cm^3
     |    nplus(levd0,lond0,lat),   ! N+  1/cm^3
     |    n2p(levd0,lond0,lat),     ! N2+ 1/cm^3
     |    nop(levd0,lond0,lat),     ! NO+  1/cm^3
     |    o2p(levd0,lond0,lat,itp), ! O2+  1/cm^3
     |    barm(levd0,lond0,lat,itp),! mean molecular weight
     |    tn  (levd0,lond0,lat,itp),! neutral temperature
     |    qji_ti(levd0,lond0,lat),  ! ion joule heating output
     |    1,nlevp1,lon0,lon1,lat)
        if (debug) write(6,"('dynamics after qjoule_ti: lat=',i3)")lat
        if (diags) then
          call addfld('QJI_TI','Joule Heating for TI',' ',
     |      qji_ti(:,i0:i1,lat),'lev',k0,k1,'lon',i0,i1,lat)
        endif
!
        call settei(
     |    tn  (levd0,lond0,lat,itp),
     |    o2  (levd0,lond0,lat,itp),
     |    o1  (levd0,lond0,lat,itp),
     |    ne  (levd0,lond0,lat,itp),
     |    te  (levd0,lond0,lat,itp),
     |    ti  (levd0,lond0,lat,itp),
     |    op  (levd0,lond0,lat,itp),
     |    o2p (levd0,lond0,lat,itp),
     |    nop (levd0,lond0,lat),
     |    barm(levd0,lond0,lat,itp),
     |    qji_ti(levd0,lond0,lat),
     |    te  (levd0,lond0,lat,itc), ! output
     |    ti  (levd0,lond0,lat,itc), ! output
     |    1,nlevp1,lon0,lon1,lat)
        if (debug) write(6,"('dynamics after settei: lat=',i3)") lat
        if (diags) then
          call addfld('T_ELEC','Electron Temperature','K',
     |      te(:,i0:i1,lat,itc),'lev',k0,k1,'lon',i0,i1,lat)
          call addfld('T_ION' ,'Ion Temperature','K',
     |      ti(:,i0:i1,lat,itc),'lev',k0,k1,'lon',i0,i1,lat)
        endif
      enddo ! lat=lat0,lat1
!
! Radiative cooling (co2, o3, no, o(3p)):
! 1/27/06 btf: sub radcool (radcool.F) replaces newton and newto3p
!              for zp-10 lbc.
!
      do lat=lat0,lat1
        call radcool(
     |    tn  (levd0,lond0,lat,itp),
     |    o2  (levd0,lond0,lat,itp),
     |    o1  (levd0,lond0,lat,itp),
     |    no  (levd0,lond0,lat,itp),
     |    barm(levd0,lond0,lat,itp),
     |    cp  (levd0,lond0,lat),
     |    cool_implicit(levd0,lond0,lat), ! output implicit cooling
     |    cool_explicit(levd0,lond0,lat), ! output explicit cooling
     |    1,nlevp1,lon0,lon1,lat)

!       call newton(
!    |    tn  (levd0,lond0,lat,itp),
!    |    o2  (levd0,lond0,lat,itp),
!    |    o1  (levd0,lond0,lat,itp),
!    |    no  (levd0,lond0,lat,itp),
!    |    barm(levd0,lond0,lat,itp),
!    |    cp  (levd0,lond0,lat),
!    |    cool_implicit(levd0,lond0,lat), ! output implicit cooling
!    |    cool_explicit(levd0,lond0,lat), ! output explicit cooling
!    |    1,nlevp1,lon0,lon1,lat)
!       if (debug) write(6,"('dynamics after newton: lat=',i3)") lat
!
! Add O(3P) contribution to cooling terms:
!       call newto3p(
!    |    tn  (levd0,lond0,lat,itp),
!    |    o1  (levd0,lond0,lat,itp),
!    |    cp  (levd0,lond0,lat),
!    |    cool_implicit(levd0,lond0,lat), ! output implicit cooling
!    |    cool_explicit(levd0,lond0,lat), ! output explicit cooling
!    |    1,nlevp1,lon0,lon1,lat)
!       if (debug) write(6,"('dynamics after newto3p: lat=',i3)") lat
!       if (diags) then
!         call addfld('COOL_IMPLICIT','Implicit cooling term','K',
!    |      te(:,i0:i1,lat,itc),'lev',k0,k1,'lon',i0,i1,lat)
!         call addfld('COOL_EXPLICIT' ,'Explicit cooling term','K',
!    |      ti(:,i0:i1,lat,itc),'lev',k0,k1,'lon',i0,i1,lat)
!       endif
      enddo ! lat=lat0,lat1
      if (debug) write(6,"('dynamics after newton,newto3p')")
!
! Calculate horizontal diffusion terms for t,u,v,o2,o1, using
! coefficients from hdif2 (hdif2 was called from advance).
!
! Make boundary longitudes available for inputs to hdif3:
      call hdif_bndlons(kldt,kldu,kldv,kldo2,kldo1,
     |    1,nlevp1,lon0,lon1,lat0,lat1)
!
! Make hdt,u,v,o2,o1:
      do lat=lat0,lat1
        call hdif3(
     |    cp(levd0,lond0,lat),     ! specific heat input
     |    kldt ,                   ! 3d input from hdif2 for tn
     |    kldu ,                   ! 3d input from hdif2 for un
     |    kldv ,                   ! 3d input from hdif2 for vn
     |    kldo2,                   ! 3d input from hdif2 for o2
     |    kldo1,                   ! 3d input from hdif2 for o1
     |    hdt (levd0,lond0,lat),   ! 2d tn output at current lat
     |    hdu (levd0,lond0,lat),   ! 2d un output at current lat
     |    hdv (levd0,lond0,lat),   ! 2d vn output at current lat
     |    hdo2(levd0,lond0,lat),   ! 2d o2 output at current lat
     |    hdo1(levd0,lond0,lat),   ! 2d o1 output at current lat
     |    1,nlevp1,lon0,lon1,lat)
      enddo ! lat=lat0,lat1
      if (debug) write(6,"('dynamics after hdif3')")
!
! Periodic points for horizontal diffusion terms output from hdif3:
! This may not be necessary.
!     call hdif_periodic(hdt,hdu,hdv,hdo2,hdo1,
!    |    1,nlevp1,lon0,lon1,lat0,lat1)
!
! Calculate joule heating for tn (3d field qji_tn):
      do lat=lat0,lat1
        call qjoule_tn(
     |    un (levd0,lond0,lat,itp), ! zonal neutral velocity input
     |    vn (levd0,lond0,lat,itp), ! meridional velocity input
     |    w  (levd0,lond0,lat,itp), ! vertical velocity input
     |    ui (levd0,lond0,lat),     ! zonal ion velocity input
     |    vi (levd0,lond0,lat),     ! meridional ion velocity input
     |    wi (levd0,lond0,lat),     ! vertical ion velocity input
     |    lam1(levd0,lond0,lat),    ! lambda_1 ion drag coefficient
     |    barm(levd0,lond0,lat,itp),! mean molecular weight
     |    tn  (levd0,lond0,lat,itp),! neutral temperature
     |    qji_tn(levd0,lond0,lat),  ! ion joule heating output
     |    1,nlevp1,lon0,lon1,lat)
        if (diags) then
          call addfld('QJI_TN','Joule Heating for TN',' ',
     |      qji_ti(:,i0:i1,lat),'lev',k0,k1,'lon',i0,i1,lat)
        endif
      enddo ! lat=lat0,lat1
      if (debug) write(6,"('dynamics after qjoule_tn')")
!
! include lower boundary from timegcm1.2
      call tuvbnd(
     |  tn   (levd0,lond0,latd0,itp),
     |  tn_nm(levd0,lond0,latd0,itp),
     |  un   (levd0,lond0,latd0,itp),
     |  un_nm(levd0,lond0,latd0,itp),
     |  vn   (levd0,lond0,latd0,itp),
     |  vn_nm(levd0,lond0,latd0,itp),
     |  w    (levd0,lond0,latd0,itp),
     |  z    (levd0,lond0,latd0,itp),    ! updated z    (s. call addiag)
     |  barm (levd0,lond0,latd0,itp),    ! updated barm (s. call addiag)
     |  cp   (levd0,lond0,latd0),
     |  hdt  (levd0,lond0,latd0),         ! horiz diffusion of T from hdif3
     |  hdu  (levd0,lond0,latd0),         ! horiz diffusion of U from hdif3
     |  hdv  (levd0,lond0,latd0),         ! horiz diffusion of V from hdif3
     |  cool_implicit(levd0,lond0,latd0), ! implicit cooling from radcool
     |  cool_explicit(levd0,lond0,latd0), ! explicit cooling from radcool
     |  ulbc   (lond0,latd0),		  ! LB for un(itp)
     |  ulbc_nm(lond0,latd0),		  ! LB for un_nm(itp)
     |  vlbc   (lond0,latd0),		  ! LB for vn(itp)
     |  vlbc_nm(lond0,latd0),		  ! LB for vn_nm(itp)
     |  1,nlevp1,lon0,lon1,lat0,lat1)
        if (debug) write(6,"('dynamics after tuvbnd: istep=',i5)") istep
!!
! Advance neutral temperature:
!
      call timer(time0,time1,'DT',0,0) ! start dt timing
      call dt(
     |  tn	(levd0,lond0,latd0,itp),
     |  tn_nm (levd0,lond0,latd0,itp),
     |  un	(levd0,lond0,latd0,itp),
     |  vn	(levd0,lond0,latd0,itp),
     |  o2	(levd0,lond0,latd0,itp),
     |  o1	(levd0,lond0,latd0,itp),
     |  barm  (levd0,lond0,latd0,itp),    ! mean molecular weight
     |  cp	(levd0,lond0,latd0),	    ! specific heat	   (cpktkm.F)
     |  kt	(levd0,lond0,latd0),	    ! molecular diffusion  (cpktkm.F)
     |  km	(levd0,lond0,latd0),	    ! molecular viscosity  (cpktkm.F)
     |  hdt	(levd0,lond0,latd0),	    ! horizontal diffusion (hdif.F)
     |  qji_tn(levd0,lond0,latd0),	    ! joule heating (sub qjoule_tn)
     |  cool_implicit(levd0,lond0,latd0), ! implicit cooling (newton.F)
     |  cool_explicit(levd0,lond0,latd0), ! explicit cooling (newton.F)
     |  w	(levd0,lond0,latd0,itc),    ! updated W (swdot.F)
     |  tn	(levd0,lond0,latd0,itc),    ! output updated tn
     |  tn_nm (levd0,lond0,latd0,itc),    ! output updated tn at time n-1
     |  1,nlevp1,lon0,lon1,lat0,lat1)
      if (debug) write(6,"('dynamics after dt')")
      call timer(time0,time1,'DT',1,0) ! end dt timing
      if (timing%level >= 2.and.time2print(nstep,istep))
     |  write(6,"('Time in DT =           ',f12.2,
     |    ' Dynamics: step ',i5)") time1,istep
      if (diags) then
        do lat=lat0,lat1
          call addfld('TN_UPD','Updated TN','K',
     |      tn(:,i0:i1,lat,itc),'lev',k0,k1,'lon',i0,i1,lat)
        enddo
      endif
!
! Advance neutral velocities:
!
      call timer(time0,time1,'DUV',0,0) ! start duv timing
      call duv(
     |  tn	(levd0,lond0,latd0,itp), ! neutral temperature
     |  tn	(levd0,lond0,latd0,itc), ! updated neutral temperature (dt.F)
     |  tn_nm (levd0,lond0,latd0,itp), ! tn at time n-1
     |  un	(levd0,lond0,latd0,itp), ! zonal velocity
     |  vn	(levd0,lond0,latd0,itp), ! meridional velocity
     |  un_nm (levd0,lond0,latd0,itp), ! zonal velocity at time n-1
     |  vn_nm (levd0,lond0,latd0,itp), ! meridional velocity at time n-1
     |  w	(levd0,lond0,latd0,itc), ! updated vertical velocity (swdot.F)
     |  barm  (levd0,lond0,latd0,itp), ! mean molecular weight
     |  z	(levd0,lond0,latd0,itp), ! geopotential height
     |  hdu	(levd0,lond0,latd0),	 ! horizontal diffusion of U (hdif3.F)
     |  hdv	(levd0,lond0,latd0),	 ! horizontal diffusion of V (hdif3.F)
     |  ui	(levd0,lond0,latd0),	 ! zonal ion velocity input
     |  vi	(levd0,lond0,latd0),	 ! meridional ion velocity input
     |  lxx	(levd0,lond0,latd0),	 ! xx ion drag coefficient
     |  lyy	(levd0,lond0,latd0),	 ! yy ion drag coefficient
     |  lxy	(levd0,lond0,latd0),	 ! xy ion drag coefficient
     |  lyx	(levd0,lond0,latd0),	 ! yx ion drag coefficient
     |  km	(levd0,lond0,latd0),	 ! molecular viscosity  (cpktkm.F)
     |  un	(levd0,lond0,latd0,itc), ! output updated un
     |  un_nm (levd0,lond0,latd0,itc), ! output updated un at time n-1
     |  vn	(levd0,lond0,latd0,itc), ! output updated vn
     |  vn_nm (levd0,lond0,latd0,itc), ! output updated vn at time n-1
     |  1,nlevp1,lon0,lon1,lat0,lat1)
      if (debug) write(6,"('dynamics after duv')")
      call timer(time0,time1,'DUV',1,0) ! end duv timing
      if (timing%level >= 2.and.time2print(nstep,istep))
     |  write(6,"('Time in DUV =          ',f12.2,
     |    ' Dynamics: step ',i5)") time1,istep
      if (diags) then
        do lat=lat0,lat1
          call addfld('UN_UPD','Updated UN','cm/s',
     |      un(:,i0:i1,lat,itc),'lev',k0,k1,'lon',i0,i1,lat)
          call addfld('VN_UPD','Updated VN','cm/s',
     |      vn(:,i0:i1,lat,itc),'lev',k0,k1,'lon',i0,i1,lat)
        enddo
      endif
!     
! Sources and sinks for major species composition O2, O:
!
      do lat=lat0,lat1
        call comp_o2o(
     |    tn   (levd0,lond0,lat,itp), ! neutral temperature
     |    o2   (levd0,lond0,lat,itp), ! molecular oxygen (mmr)
     |    o1   (levd0,lond0,lat,itp), ! atomic oxygen (mmr)
     |    barm (levd0,lond0,lat,itp), ! mean molecular weight
     |    op   (levd0,lond0,lat,itp), ! O+
     |    no   (levd0,lond0,lat,itp), ! NO
     |    n4s  (levd0,lond0,lat,itp), ! N(4S)
     |    n2d  (levd0,lond0,lat,itp), ! N(2D)
     |    o2p  (levd0,lond0,lat,itp), ! O2+
     |    ne   (levd0,lond0,lat,itp), ! electron density
     |    n2p  (levd0,lond0,lat),     ! N2+
     |    nplus(levd0,lond0,lat),     ! N+
     |    nop  (levd0,lond0,lat),     ! NO+
     |    1,nlevp1,lon0,lon1,lat)
      enddo ! lat=lat0,lat1
      if (debug) write(6,"('dynamics after comp_o2o')")
!
! Advance O2, O:
!
      time1_cmpmajor = 0.
      call timer(time0,time1,'CMPMAJOR',0,0) ! start comp major timing
      call comp_major(
     |  tn    (levd0,lond0,latd0,itp), ! neutral temperature
     |  o2    (levd0,lond0,latd0,itp), ! O2 (mmr)
     |  o2_nm (levd0,lond0,latd0,itp), ! O2 (mmr) at time n-1
     |  o1    (levd0,lond0,latd0,itp), ! O1 (mmr)
     |  o1_nm (levd0,lond0,latd0,itp), ! O1 (mmr) at time n-1
     |  un    (levd0,lond0,latd0,itp), ! zonal velocity
     |  vn    (levd0,lond0,latd0,itp), ! meridional velocity
     |  w     (levd0,lond0,latd0,itp), ! vertical velocity
     |  hdo2  (levd0,lond0,latd0),     ! O2 horizontal diffusion (hdif3)
     |  hdo1  (levd0,lond0,latd0),     ! O  horizontal diffusion (hdif3)
     |  o2    (levd0,lond0,latd0,itc), ! output: O2 updated for current step 
     |  o2_nm (levd0,lond0,latd0,itc), ! output: O2 updated for previous step
     |  o1    (levd0,lond0,latd0,itc), ! output: O1 updated for current step
     |  o1_nm (levd0,lond0,latd0,itc), ! output: O1 updated for previous step
     |  1,nlevp1,lon0,lon1,lat0,lat1)
      if (debug) write(6,"('dynamics after comp')")
      call timer(time0,time1,'CMPMAJOR',1,0) ! suspend comp major timing
      time1_cmpmajor = time1_cmpmajor+time1
      if (timing%level >= 2.and.time2print(nstep,istep))
     |  write(6,"('Time in COMP=          ',f12.2,
     |    ' Dynamics: step ',i5)") time1,istep
      if (timing%level >= 2.and.time2print(nstep,istep))
     |  write(6,"('Time in CMPMAJOR =     ',f12.2,
     |    ' Dynamics: step ',i5)") time1_cmpmajor,istep
      if (diags) then
        do lat=lat0,lat1
          call addfld('O2_UPD','Updated O2','mmr',
     |      o2(:,i0:i1,lat,itc),'lev',k0,k1,'lon',i0,i1,lat)
          call addfld('O1_UPD','Updated O1','mmr',
     |      o1(:,i0:i1,lat,itc),'lev',k0,k1,'lon',i0,i1,lat)
        enddo
      endif
      if (debug) write(6,"('dynamics returning')")
      end subroutine dynamics