Modelling of magnetic fields of CP stars II. Analysis of longitudinal field, crossover, and quadratic field observations

In recent years, the introduction and systematic application of new diagnos tic techniques has enormously increased the opportunities to investigate ma gnetic fields of chemically peculiar (CP) stars. To approach the problem of modelling these fields, in previous papers we set up a theory aimed at des cribing the magnetic configuration due to the superposition of a dipole wit h an arbitrary quadrupole. The present work is a first application of this theory to spectro-polarimetric observations of Stokes I and V. We have atte mpted to model nine magnetic CP stars by analysing their curves of longitud inal field, crossover and quadratic field. We found that the classical dipo lar model is adequate in only one case, while in six cases it should defini tely be ruled out. For two stars a specific dipole plus quadrupole model ha s been recovered.