The test of the boundary in the closed region with that it opens
subroutine zsub33(ia,aa)

Description: The test result is handed in ainte1 from three-dimensional line of magnetic force of the earth's magnetosphere, in order to use with ainte1a result, and by selecting line of magnetic force which exists in the narrow region between open open region and closed region, in order to describe only the chosen line of magnetic force. 

Input variable:
      nxg=ia(1) : Data number of the x direction in the starting point of line of magnetic force
      nyg=ia(2) : Data number of the x direction in the starting point of line of magnetic force

Relating subroutine:
      ainte1a(ia,aa,f,p)
      ainte1(ia,aa,f,p)