Understanding pulsar magnetospheres with the SKAO

TL;DR

Understanding pulsar magnetospheres hinges on connecting geometry, intrinsic emission, variability, and global magnetospheric physics to a wealth of multi-wavelength data. The paper argues that SKA's sensitivity, broad bandwidths, and sub-arraying will enable both large-scale population studies and in-depth analyses of individual sources, including the double pulsar, while tying in gamma-ray, X-ray, and UV observations to advanced simulations. It outlines five core science questions and describes how SKA capabilities will address them through wide-field surveys, high-cadence monitoring, and coordinated multi-wavelength follow-ups, thus advancing models of magnetic-field geometry, emission mechanisms, and magnetospheric dynamics. The findings are poised to refine theories of dipole versus non-dipole fields, constrain radio luminosities and emission physics, and illuminate connections among pulsars, magnetars, FRBs, and long-period transients. Overall, SKA-driven monitoring and targeted studies will yield a cohesive, physically grounded picture of pulsar magnetospheres with broad implications for gravitational-wave timing and plasma physics.

Abstract

The SKA telescopes will bring unparalleled sensitivity across a broad radio band, a wide field of view across the Southern sky, and the capacity for sub-arraying, all of which make them the ideal instruments for studying the pulsar magnetosphere. This paper describes the advances that have been made in pulsar magnetosphere physics over the last decade, and details how these have been made possible through the advances of modern radio telescopes, particularly SKA precursors and pathfinders. It explains how the SKA telescopes would transform the field of pulsar magnetosphere physics through a combination of large-scale monitoring surveys and in-depth follow-up observations of unique sources and new discoveries. Finally, it describes how the specific observing opportunities available with the AA* and AA4 configurations will achieve the advances necessary to solve the problem of pulsar radio emission physics in the coming years.

Figures (5)

• Figure 1: Average of four MeerKAT UHF polarization light curves of PSR J0737$-$3039A being eclipsed by the truncated dipolar magnetosphere of PSR J0737$-$3039B. Top panel shows the linear polarization position angle ($\Psi$), middle is the ellipticity angle ($\chi$) and the lower panel depicts the changes in total intensity ($I$; black solid line), total linear polarization ($L$; dashed orange line) and circular polarization ($V$; dash-dotted purple line).
• Figure 2: Two examples of integrated pulse profiles of pulsars observed with the Murriyang radio telescope using its Ultra-Wideband receiver. The full frequency resolution of the receiver (704--4032 MHz) is split into 8 subbands, and the pulse profiles displayed here are taken from the subband centred at 1400 MHz. In each case the top subplot shows the position angle (PA) of the linear polarization, and the bottom subplot shows the total intensity (black), linear polarization (red) and circular polarization (blue) of the pulse profile.
• Figure 3: An example of a pulsar with profile variability as identified in the Thousand-Pulsar-Array project with MeerKAT. The figure is similar to that in bwk+24, but includes more recent data. The top panel shows the average pulse profile of PSR J1141$-$3322. The colour map in the lower left panel shows the phase resolved temporal evolution of profile shape of the pulsar (for details see bwk+24). The lower right panel shows the variations of $\dot \nu$ over the secular spin-down rate. An excess of emission associated with the trailing component can be seen to be mildly correlated with the increase in spin-down rate.
• Figure 4: Illustration of the dipolar magnetic field of a pulsar where key regions of interest are highlighted. The inner and outer magnetosphere are defined by the regions within and beyond the light-cylinder radius, indicated by the orange cylinder, where the co-rotation velocity exceeds the vacuum speed of light. Electromagnetic radiation is generated in the shaded regions, with radio emission originating from the polar cap (pink) and potentially the separatrix (yellow). High-energy non-thermal emission, including gamma-rays, is thought to originate from the current sheet beyond the Y-point (yellow; as opposed to older models prescribing radiation from the "outer gap", purple). Thermal X-ray emission arises from the hotspots (light blue regions on the central neutron star) where energetic particles, which are produced by the pair production discharges, bombard the stellar surface in the open field line region.
• Figure 5: This figure shows all of the pulsars discovered to date which have both a measured period $P$ and period derivative $\dot{P}$, as a function of those two variables. The pulsars are shown with small black dots, and a Gaussian kernel density estimation of the whole distribution is shown in green. A total of 4,343 pulsars have been discovered, of which 2,816 have a measurement of $\dot{P}$. Data taken from the pulsar catalogue psrcatManchester2005 on 6th July 2025.