  This thesis research focusses on the study of the young and energetic
isolated ordinary pulsar population detected by the Fermi gamma-ray space
telescope. We compared the model expectations of four emission models and the
LAT data. We found that all the models fail to reproduce the LAT detections, in
particular the large number of high spin-down power objects observed. This
inconsistency is not model dependent. A discrepancy between the
radio-loud/radio-quiet objects ratio was also found between the observed and
predicted samples. The gamma-ray luminosity proportional to the 0.5 power of
the spin-down power relation is robustly confirmed by all the assumed models
with particular agreement in the slot gap (SG) case. On luminosity bases, the
intermediate altitude emission of the two pole caustic SG model is favoured.
The beaming factor shows an spin-down power dependency that is slightly visible
in theSG case. Estimates of the pulsar orientations have been obtained to
explain the simultaneous gamma and radio light-curves. By analysing the
solutions we found a relation between the observed energy cutoff and the width
of the emission slot gap. This relation has been theoretically predicted. A
possible magnetic obliquity alignment with time is rejected -for all the
models- on timescale of the order of a million years. The light-curve
morphology study shows that the outer magnetosphere gap emission are favoured
to explain the observed radio-gamma lag. The light curve moment studies
(symmetry and sharpness) on the contrary favour a two pole caustic slot gap
emission. All the model predictions suggest a different magnetic field layout
with an hybrid two pole caustic and intermediate altitude emission to explain
both the pulsar luminosity and light curve morphology . The low magnetosphere
emission mechanism of the polar cap model, is systematically rejected by all
the tests done.
