Properties of matter in ultrahigh magnetic fields and the structure of the surface of neutron stars

The physical properties of atoms, molecules, and solids in ultrahigh magnetic fields $B\gg10^9$ G that are believed to exist on the surface of neutron stars are discussed. In these fields, atoms are strongly deformed and elongated along the magnetic field lines; the binding energy and ionizing energy of the atoms are substantially increased and the interatomic interaction is dramatically changed. This strongly modifies the properties of matter at the surface of magnetic neutron stars which are crucial for modelling the pulsar magnetosphere. A scenario for magnetosphere evolution is proposed which suggests free emission for a young pulsar and strong binding of the matter to the surface at a later stage. This later stage is due to strongly bound chains of alternate heavy atoms and light atoms accreted on the surface of the star.