/*GrnVryDpth set grains abundance as a function of depth into cloud*/
#include "cddefines.h"
#include "grainvar.h"
#include "ionfracs.h"
#include "grnvrydpth.h"

double GrnVryDpth(
						/* pointer to grain type */
						long int nd)
{
	float GrnVryDpth_v;

#	ifdef DEBUG_FUN
	fputs( "<+>GrnVryDpth()\n", debug_fp );
#	endif

	/*set grains abundance as a function of depth into cloud
	 *NB most quantities are undefined for first calls to this sub */
	/* nd is the pointer to the grain species.  This routine must return
	 * a scale factor for the abundance at this position.
	 * */

	if( GrainVar.lgDustVary[nd] )
	{
		/* sample code - the scale factor will be the hydrogen ionization fraction
		 * following can be used for any other element - first dimesion
		 * is atomic weight and second is stage of ionization */
		GrnVryDpth_v = xIonFracs[1][0]/(xIonFracs[2][0] + 
		  xIonFracs[1][0]);
	}
	else
	{
		GrnVryDpth_v = 1.;
	}


#	ifdef DEBUG_FUN
	fputs( " <->GrnVryDpth()\n", debug_fp );
#	endif
	return( GrnVryDpth_v );
}