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C $Id: tnf.f 3304 2011-01-17 15:25:59Z brideout $
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C
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DOUBLE PRECISION FUNCTION TNF(TI,TE,NE,NHP,NO,NH,NN2,NO2,NHE,IER)
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C
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C TNF calculates the neutral temperature (tn) given the electron and
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C neutral temperatures (TE, TN) and the electron, o+, h+, o, h,
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C n2, o2 and he concentrations (NE, NOP, NHP, NO, NH, NN2, NO2,
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C NHE). o+ and h+ ions are assumed to be the only ions present.
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C only coulomb collisions and ion-neutral polarization and
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C charge-exchange interactions are considered in balancing
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C the ion gas energy source and sink terms. the solution for
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C tn is an iterative procedure in which TI is the initial value
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C of tn for the first iteration. all concentrations are in
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C units of cm**-3.
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C
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C Input:
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C TI - Ion Temperature (K)
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C TE - Electron Temperature
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C NE - Electron concentration (cm**-3)
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C NHP - H Ion concentration
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C NO - O concentration
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C NH - H concentration
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C NN2 - N2 concentration
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C NO2 - O2 concentration
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C NHE - HE concentration
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C
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C Output:
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C IER - If (IER.NE.0) an error has occurred.
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C
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C .. Scalar Arguments ..
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DOUBLE PRECISION NE,NH,NHE,NHP,NN2,NO,NO2,TE,TI
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INTEGER IER
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C ..
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C .. Local Scalars ..
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DOUBLE PRECISION ALOGEI,ALOGT1,ALOGT2,ALOGT3,CEI,CHPH,CHPN,
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* CHPO,CONST,CONVRG,COPH,COPN,COPO,COULOG,DIVRG,
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* DTEST,FACTOR,FEI,FHPN,FOPN,NOP,QHPH,QHPO,QOPH,
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* QOPO,SQRTT1,T1,T2,T3,TECUBE,TEPTI,TN,TNSAVE
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INTEGER ITER,NITER
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C ..
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C .. Intrinsic Functions ..
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INTRINSIC ABS,DEXP,DLOG,DSQRT
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C ..
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C .. Data statements ..
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C
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DATA CONVRG/1.0D0/,NITER/10/,DIVRG/1.D20/
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C ..
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IER = 0
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TNF = 0.0D0
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C
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C .....check input parameters.....
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C write(16,"(5e13.5)") ti,te,ne,nhp,no,nh,nn2,no2,nhe
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IF (TE.LT.TI .OR. NE.LT.1.D0 .OR. NE.GT.1.D10 .OR.
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* NHP.LT.0.D0 .OR. NHP.GT.1.D10 .OR. NO.LT.0.D0 .OR.
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* NO.GT.1.D20 .OR. NH.LT.0.D0 .OR. NH.GT.1.D20 .OR.
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* NN2.LT.0.D0 .OR. NN2.GT.1.D20 .OR. NO2.LT.0.D0 .OR.
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* NO2.GT.1.D20 .OR. NHE.LT.0.D0 .OR. NHE.GT.1.D20) THEN
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TNF = 0.0D0
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IER = 3
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ELSE
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C
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C NHP - H+ CONCENTRATION
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C
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NOP = NE - NHP
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TECUBE = TE**3
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C LEI COEFF.
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CEI = (3.22D-8*NOP+51.12D-8*NHP)*NE/DSQRT(TECUBE)
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ALOGEI = DLOG(1.D0+TE/TI)
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TEPTI = TE + TI
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C .....lin.....
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C O+ POLARIZATION
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COPN = 6.6D-14*NN2 + 5.8D-14*NO2 + 2.8D-14*NHE
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C H+ POLARIZATION
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CHPN = 3.1D-14*NN2 + 2.8D-14*NO2 + 5.5D-14*NHE
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C
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TN = TI
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ITER = 0
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C
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10 CONTINUE
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TNSAVE = TN
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T1 = TI + TN
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IF (T1.LT.0.0D0) GO TO 60
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SQRTT1 = DSQRT(T1)
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ALOGT1 = DLOG(T1)
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T2 = TI + .063D0*TN
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IF (T2.LT.0.0D0) GO TO 50
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ALOGT2 = DLOG(T2)
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T3 = TN + .063D0*TI
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IF (T3.LT.0.0D0) GO TO 40
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ALOGT3 = DLOG(T3)
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C O+O CHARGE EXCHANGE
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COPO = .00627D-14*NO*SQRTT1
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C H+H CHARGE EXCHANGE
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CONST = .02498D-14*NH
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CHPH = CONST*SQRTT1
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C H+O CHARGE EXCHANGE
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CHPO = .02498D-14*NO*DSQRT(T2)
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C ..... o+h charge exchange coefficient.....
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COPH = CONST*DSQRT(T3)*(5.D0+3.D0*DEXP(-227.8D0/TE)+
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* DEXP(-325.6D0/TE))/8.D0
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C Coulomb Logarithm from Itikawa (JATP, 1975)
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COULOG = 8.06 + 0.5D0 * DLOG(TECUBE/NE)
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C qopo = (7.47-.206*dlogt1)**2
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QOPO = 58.3D0
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C H+H
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QHPH = (10.2D0-.360D0*ALOGT1)**2
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C H+O
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QHPO = (4.26D0-.0869D0*ALOGT2)**2
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C O+H
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QOPH = (4.26D0-.0869D0*ALOGT3)**2
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C E-I HEAT EXCHANGE
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FEI = CEI*COULOG
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C O+ N HEAT EXCHANGE
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FOPN = (COPN+COPO*QOPO+COPH*QOPH)*NOP
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C H+ N HEAT EXCHANGE
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FHPN = (CHPN+CHPH*QHPH+CHPO*QHPO)*NHP
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FACTOR = FEI/(FOPN+FHPN)
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TN = (1.D0+FACTOR)*TI - FACTOR*TE
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DTEST = ABS(TN-TNSAVE)
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IF (DTEST.GE.DIVRG) GO TO 30
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ITER = ITER + 1
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IF (ITER.GT.NITER) GO TO 20
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IF (DTEST.GT.CONVRG) GO TO 10
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TNF = TN
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GO TO 70
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20 CONTINUE
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TN = 0.0D0
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IER = 2
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GO TO 70
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30 CONTINUE
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TN = 0.0D0
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IER = 1
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GO TO 70
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40 CONTINUE
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TN = 0.0D0
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IER = 1
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GO TO 70
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50 CONTINUE
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TN = 0.0D0
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IER = 1
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GO TO 70
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60 CONTINUE
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TN = 0.0D0
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IER = 1
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END IF
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70 CONTINUE
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RETURN
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END
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