Setting bounding constraints

This section allows for specification of upper and/or lower bounding values for susceptibilities of each cell. There are three ways of specifying bounds:

1. Default: If the user chooses to not define upper and lower bounds, the program employs default bounds for susceptibilities in every cell of 1.0 and 0.0 respectively (S.I. units). While it is true that some rocks have susceptibility greater than 1.0, MAG3D Version 4.0 still assumes small susceptibilities, as this code has done since the original version. When there are very high susceptibilities, the relation between incident and induced magnetization is no longer linear, and the problem becomes more complicated. Inverting data in the presence of very high susceptibilities is still a topic of research, and MAG3D Version 4.0 does not allow for high susceptibilities in the solution.
2. Upper and lower values: Use this option if you want to set a single upper bound value and a single lower bound for all cells.
3. Using a file: Each cells can have individual upper and lower bounds if a bounds.sus file is specified. See the MAG3D manual Chapter 2.