  The concept of hyperbolic flux tubes (HFTs) is a generalization of the
concept of separator field lines for coronal magnetic fields with a trivial
magnetic topology. An effective mechanism of a current layer formation in HFTs
is proposed. This mechanism is called magnetic pinching and it is caused by
large-scale shearing motions applied to the photospheric feet of HFTs in a way
as if trying to twist the HFT. It is shown that in the middle of an HFT such
motions produce a hyperbolic flow that causes an exponentially fast growth of
the current density in a thin force-free current layer. The magnetic energy
associated with the current layer that is built up over a few hours is
sufficient for a large flare. Other implications of HFT pinching for solar
flares are discussed as well.
