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/* This file is part of Cloudy and is copyright (C)1978-2008 by Gary J. Ferland and
 * others.  For conditions of distribution and use see copyright notice in license.txt */
/* atmdat_HS_caseB - interpolate on line emissivities from Storey & Hummer tables for hydrogen */
#include "cddefines.h"  
#include "atmdat.h"  

double atmdat_HS_caseB( 
          /* upper and lower quantum numbers*/
          long int iHi, 
          long int iLo, 
          /* element number, 1 or 2 at this point, but decremented to C scale later */
          long int nelem, 
          /* temperature to interpolate, for H between 500-30,000K*/
          double TempIn, 
          /* density to interpolate */
          double DenIn,
          /* case - 'a' or 'b' */
          char chCase )

/* general utility to interpolate line emissivities from the Storey & Hummer tables
 of case B emissivities.  
 iHi<25, iLo, the principal quantum
 numbers, and are upper and lower levels in any order.  
 nelem element number on physicial scale, 1 or 2 have data
 TempIn = temperature, and must lie within the range of the table, which depends on
 the ion charge, and is 500 - 30,000K for hydrogen.  
 DenIn is the density and must not exceed the high density limit to the table.  

 routine returns -1 if conditions outside temperature range, or
 above density range of tabulated case b results
 If desired density is low limit, lower limit is used instead 
*/

{
        long int 
                ipTemp, /*pointer to temperature*/
                ipDens, /*pointer to density*/
                ipDensHi ,
                ipTempHi;
        int ipUp , ipLo , ip;
        double x1 , x2 , yy1 , yy2 , z1 , z2 , za , zb ,z;
        int iCase;

        DEBUG_ENTRY( "atmdat_HS_caseB()" );

        /*make sure nelem is 1 or 2*/
        if( nelem<ipHYDROGEN || nelem> HS_NZ )
        {
                printf("atmdat_HS_caseB called with improper nelem, was%li and must be 1 or 2",nelem);
                cdEXIT(EXIT_FAILURE);

        }
        /* now back nelem back one, to be on c scale */
        --nelem;

        /* case A or B? */
        if( chCase == 'a' || chCase=='A' )
        {
                iCase = 0;
        }
        else if(  chCase == 'b' || chCase=='B' )
        {
                iCase = 1;
        }
        else
        {
                iCase = false;
                printf("atmdat_HS_caseB called with improper case, was %c and must be A or B",chCase);
                cdEXIT(EXIT_FAILURE);
        }

        /*===========================================================*/
        /* following is option to have principal quantum number given in either order, 
         * final result is that ipUp and ipLo will be the upper and lower levels */
        if( iHi > iLo )
        {
                ipUp = (int)iHi;  ipLo = (int)iLo;
        }
        else if( iHi < iLo )
        {
                ipUp = (int)iLo; ipLo = (int)iHi;
        }
        else
        { 
                printf("atmdat_HS_caseB called with indices equal, %ld  %ld  \n",iHi,iLo);
                cdEXIT(EXIT_FAILURE);
        }

        /* now check that they are in range of the predicted levels of their model atom*/
        if( ipLo <1 ) 
        {
                printf(" atmdat_HS_caseB called with lower quantum number less than 1, = %i\n",
                        ipLo);
                cdEXIT(EXIT_FAILURE);
        }

        if( ipUp >25 ) 
        {
                printf(" atmdat_HS_caseB called with upper quantum number greater than 25, = %i\n",
                        ipUp);
                cdEXIT(EXIT_FAILURE);
        }

        /*===========================================================*/
        /*bail if above high density limit */
        if( DenIn > atmdat.Density[iCase][nelem][atmdat.nDensity[iCase][nelem]-1] ) 
        {
                /* this is flag saying bogus results */
                return -1;
        }

        if( DenIn <= atmdat.Density[iCase][nelem][0] )
        {
                /* this case, desired density is below lower limit to table,
                 * just use the lower limit */
                ipDens = 0;
        }
        else
        {
                /* this case find where within table density lies */
                for( ipDens=0; ipDens < atmdat.nDensity[iCase][nelem]-1; ipDens++ )
                {
                        if( DenIn >= atmdat.Density[iCase][nelem][ipDens] && 
                                DenIn < atmdat.Density[iCase][nelem][ipDens+1] ) break;
                }
        }


        /*===========================================================*/
        /* confirm within temperature range*/
        if( TempIn < atmdat.ElecTemp[iCase][nelem][0] || 
                TempIn > atmdat.ElecTemp[iCase][nelem][atmdat.ntemp[iCase][nelem]-1] ) 
        {
                /* this is flag saying bogus results */
                return -1;
        }

        /* find where within grid this temperature lies */ 
        for( ipTemp=0; ipTemp < atmdat.ntemp[iCase][nelem]-1; ipTemp++ )
        {
                if( TempIn >= atmdat.ElecTemp[iCase][nelem][ipTemp] && 
                        TempIn < atmdat.ElecTemp[iCase][nelem][ipTemp+1] ) break;
        }

        /*===========================================================*/
        /*we now have the array indices within the temperature array*/

        if( ipDens+1 > atmdat.nDensity[iCase][nelem]-1 )
        { 
                /* special case, when cell is highest density point */
                ipDensHi = atmdat.nDensity[iCase][nelem]-1;
        }
        else if( DenIn < atmdat.Density[iCase][nelem][0])
        {
                 /* or density below lower limit to table, set both bounds to 0 */
                ipDensHi = 0;
        }
        else
        { 
                ipDensHi = ipDens+1;
        }

        /*special case, if cell is highest temperature point*/
        if( ipTemp+1 > atmdat.ntemp[iCase][nelem]-1 )
        { 
                ipTempHi = atmdat.ntemp[iCase][nelem]-1;
        }
        else
        { 
                ipTempHi = ipTemp+1;
        }

        x1 = log10( atmdat.Density[iCase][nelem][ipDens] );
        x2 = log10( atmdat.Density[iCase][nelem][ipDensHi] );

        yy1 = log10( atmdat.ElecTemp[iCase][nelem][ipTemp] );
        yy2 = log10( atmdat.ElecTemp[iCase][nelem][ipTempHi] );

        /*now generate the index to the array, expression from Storey code -1 for c*/
        ip = (int)((((atmdat.ncut[iCase][nelem]-ipUp)*(atmdat.ncut[iCase][nelem]+ipUp-1))/2)+ipLo - 1);

        /*pointer must lie within line array*/
        ASSERT( ip < NLINEHS ); 
        ASSERT( ip >= 0 );

        /* interpolate on emission rate*/
        z1 = log10( atmdat.Emiss[iCase][nelem][ipTemp][ipDens][ip]);
        z2 = log10( atmdat.Emiss[iCase][nelem][ipTemp][ipDensHi][ip]);

        if( fp_equal( x2, x1 ) ) 
        {
                za = z2;
        }
        else 
        {
                za = z1 + log10( DenIn / atmdat.Density[iCase][nelem][ipDens] ) * (z2-z1)/(x2-x1);
        }

        z1 = log10( atmdat.Emiss[iCase][nelem][ipTempHi][ipDens][ip]);
        z2 = log10( atmdat.Emiss[iCase][nelem][ipTempHi][ipDensHi][ip]);

        if( fp_equal( x2, x1 ) )
        {
                zb = z2;
        }
        else 
        {
                zb = z1 + log10( DenIn / atmdat.Density[iCase][nelem][ipDens] ) * (z2-z1)/(x2-x1);
        }

        if( fp_equal( yy2, yy1 ) )
        {
                z = zb;
        }
        else 
        {
                z = za + log10( TempIn / atmdat.ElecTemp[iCase][nelem][ipTemp] ) * (zb-za)/(yy2-yy1);
        }

        return ( pow(10.,z) );
}

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