Pulsars and neutron stars/Pulsar rotation measures

Measuring pulsar rotation measures

Pulsar rotation measures (RMs) are measured by fitting the position angle of the linear polarization over a range of observing frequencies as:

$\psi ={\rm {RM}}\lambda ^{2}$

where $\lambda =c/f$ where $f$ is the observing frequency.

Measured pulsar RMs vary, in part, because of the Earth's ionosphere. This ionospheric correction can be estimated using the International Reference Ionosphere (IRI) model.