Jurčák criterion states that umbra-penumbra boundaries are defined by a
constant vertical magnetic field in stable sunspots. In this seminar I
will talk about the vertical magnetic field on the boundary of an evolving
pore. SDO/HMI vector field maps provide a temporal cadence that allow us
to investigate the connection between the strengthening and weakening of
the vertical magnetic field, and the stability and posterior dissipation
of the pore. This analysis shows a relation between the stability of the
pore and the Jurčák criterion.