Probing Magnetospheres of Rotation-Driven Neutron Stars

Abstract

Magnetospheric issues are discussed as they relate to radio intensity variations, spindown, rotational noise, and emission altitudes. Radio fluctuations trace the overall state(s) of the magnetosphere in spite of the fact that L_radio ≪ IΩ. Five methods for estimating emission altitudes r_e are discussed. Four measure either the transverse width or radial depth of the emission region; assumption of a dipolar field and, in some cases, a radius to frequency mapping, yields estimates for the absolute radius of the emission region. The fifth method (v/c effects in Stokes parameter waveforms) provides direct altitude estimates. Most results suggest that r_e ≲ 0.02 R_LC at v = 0.4 GHz. A radius to frequency mapping appears viable for some but not necessarily all objects. The mapping need not be one-to-one. Prospects are discussed for using simultaneous radio and high energy observations to make further progress in our understanding of magnetospheres.