  For a planet to be considered habitable on its surface, it is an important
advantage for it to have a magnetic field that protects its atmosphere from
stellar winds as well as cosmic rays. Magnetic protection of potentially
habitable planets plays a key role in determining the chances of detecting
atmospheric biosignatures. This paper proposes to use the Preliminary Reference
Earth Model (PREM) internal structure as the base of a numerical model. With
this model, we estimate the magnetic properties of dry and water-rich
Earth-like and Super-Earth-like planets. We apply it to those of this kind at
the first 176 planets confirmed by TESS. Using PREM as a reference, we estimate
the internal structure of dry and water-rich rocky planets. This model provides
an estimation of the average density and core size of the planet and, with
them, its magnetic moment depending on whether it is tidally locked or not. Our
model estimates the thermodynamic variables as a function of pressure and
includes saltwater as a component of water-rich exoplanets. We have not used
the perfect layer differentiation approximation. We have validated our model
with those planets and satellites in the Solar system with similar
characteristics. The differences with the observed values in the internal
structure characteristics, mass, average density, moment of inertia factor, and
local Rossby number are remarkably low or even negligible. The estimated
magnetic moments are also very similar to the observed ones. We have applied
the model to the first 176 planets confirmed by the TESS, finding that, from an
astrobiological perspective TOI-700 d and TOI-2257 b are the most interesting
ones as being located in the habitable zone (HZ), although their magnetic
moments are only about 0.01 of the Earth's magnetic moment.
