According to the partially screened gap scenario , an efficient electron-positron pair creation , a general precondition of radio-pulsar activity , relies on the existence of magnetic spots , i.e. , local concentrations of strong and small scale magnetic field structures at the surface of neutron stars .
They have a strong impact on the surface temperature , which is potentially observable .
Here we reinforce the idea that such magnetic spots can be formed by extracting magnetic energy from the toroidal field that resides in deep crustal layers , via Hall drift .
We study and discuss the magneto-thermal evolution of qualitatively different neutron star models and initial magnetic field configurations that lead to the creation of magnetic spots .
We find that magnetic spots can be created on a timescale of 10 ^ { 4 } years with magnetic field strengths \gtrsim 5 \times 10 ^ { 13 } G , provided almost the whole magnetic energy is stored in its toroidal component , and that the conductivity in the inner crust is not too large .
The lifetime of the magnetic spots is at least \sim one million of years , being longer if the initial field permeates both core and crust .