Testing the accuracy of the ionospheric Faraday rotation corrections through LOFAR observations of bright northern pulsars

N. K. Porayko (1) , A. Noutsos (1) , C. Tiburzi (1) , J. P. W. Verbiest (1) , A. Horneffer (1) , J Künsemöller (2) , S. Osłowski (3) , A Kramer (1) , A Schnitzeler (1) , J. M. Anderson , M Brüggen (4) , Jean-Mathias Griessmeier (5, 6) , M. Hoeft , D. J. Schwarz , M. Serylak (6) , O. Wucknitz (1)

1 MPIFR - Max-Planck-Institut für Radioastronomie
2 Universität Bielefeld
3 Swinburne University of Technology [Melbourne]
4 University of Hamburg
5 LPC2E - Laboratoire de Physique et Chimie de l'Environnement et de l'Espace
6 USN - Unité Scientifique de la Station de Nançay

Faraday rotation of polarized emission from pulsars measured at radio frequencies provides a powerful tool to investigate the interstellar and interplanetary magnetic fields. However, besides being sensitive to the astrophysical media, pulsar observations in radio are affected by the highly time-variable ionosphere. In this article, the amount of ionospheric Faraday rotation has been computed by assuming a thin layer model. For this aim, ionospheric maps of the free electron density (based on Global Positioning System data) and semi-empirical geomagnetic models are needed. Through the data of five highly polarized pulsars observed with the individual German LOw-Frequency ARray stations, we investigate the performances of the ionospheric modelling. In addition, we estimate the parameters of the systematics and the correlated noise generated by the residual unmodelled ionospheric effects, and show the comparison of the different free-electron density maps. For the best ionospheric maps, we have found that the rotation measure corrections on 1 yr time-scales after subtraction of diurnal periodicity are accurate to similar to 0.06-0.07 rad m(-2).

Keywords: polarization; atmospheric effects; stars: neutron; pulsars: general

Domains: Sciences of the Universe [physics]; Astrophysics [astro-ph]; Solar and Stellar Astrophysics [astro-ph.SR]; Physics [physics]; Physics [physics]; Astrophysics [astro-ph]

N. K. Porayko, A. Noutsos, C. Tiburzi, J. P. W. Verbiest, A. Horneffer, et al.. Testing the accuracy of the ionospheric Faraday rotation corrections through LOFAR observations of bright northern pulsars. Monthly Notices of the Royal Astronomical Society, 2019, 483 (3), pp.4100-4113. ⟨10.1093/mnras/sty3324⟩. ⟨insu-02177535⟩