The FACs are not by definition balanced in an analysis grid since we use spherical elementary currents and our analysis regions are in general not global. That is ok with some regional analyses (we could happen to look at a region dominated by upward current, for example), but sometimes the physics indicates that the upward and downward currents should be balanced. For example, if we model the full hemisphere, there should probably not be a net current in to or out of the analysis region. We could add an optional regularization term to enforce this.
The FACs are not by definition balanced in an analysis grid since we use spherical elementary currents and our analysis regions are in general not global. That is ok with some regional analyses (we could happen to look at a region dominated by upward current, for example), but sometimes the physics indicates that the upward and downward currents should be balanced. For example, if we model the full hemisphere, there should probably not be a net current in to or out of the analysis region. We could add an optional regularization term to enforce this.