1996A&A...309..481X

Pulsar polarimetric observations, conducted at the highest frequency ever, 32GHz, have been used to probe the emission properties of pulsar radiation at mm-wavelengths. The sample consists of eight nearby, relatively-young pulsars, located above the 5-Myr luminosity line. The flatter spectral indices characterizing the pulsars in this sample do not show any correlation with observed and derived parameters often used to describe pulsar properties. Simple Gaussian profiles and depolarized emission are the general properties that characterise pulsar emission in this newly-explored spectral region. However, an investigation of the frequency dependence of the fundamental emission characteristics (i.e. flux density, modulation index, profile frequency-development and polarization properties) indicates that there are high- and low-frequency regimes between which the character of the emission is markedly different. Assuming circularly-symmetric emission zones, as well as dipolar magnetic field configurations, the altitude of the mm-wavelength emission is estimated. This height is generally located at 10R*, while the radial height distribution is fairly compact. The dominance of the dipole magnetic field throughout the emission region is supported by the persistence of the polarization position angle swing with pulse longitude and the asymptotic narrowing of the profile widths over the widest range of frequencies yet examined.