The polarization of the drifting sub-pulses from PSR B1919+21

Abstract

Aims. We aim to expand our understanding of radio wave emission and propagation in the pulsar magnetosphere by studying the polarization of drifting sub-pulses in highly sensitive observations of PSR~B1919+21 recorded at the Arecibo Observatory. Methods. We apply and compare several methods of analysis and visualization, including eigenvalue analysis of the longitude-resolved covariances between the Stokes parameters; longitude-resolved scatter plots of the normalised Stokes vectors in the Poincaré sphere; auto- and cross-correlations between the Stokes parameters as a function of offset in pulse longitude and lag in pulse number; and mean drift bands of polarization state, formed by averaging the Stokes parameters and quantities derived from them synchronously with the drifting sub-pulse modulation period. Results. We observe regions of pulse longitude where the superposition of orthogonally polarised modes is best described as incoherent and regions where the superposition appears to be at least partially coherent. Within the region of coherent superposition, over a range of pulse longitudes spanning $\sim 2\circ$, the distribution of the Stokes polarization vectors forms a torus centered near the origin of the Poincaré sphere. Furthermore, the polarization vectors rotate about the axis of revolution of the torus synchronously with the drifting sub-pulse modulation of the total intensity. Conclusions. The nearly uniform circular modulation of polarization state, clearly evident in both the toroidal distribution of the Stokes polarization vectors and the mean drift bands of the Stokes parameters, is not predicted by current theoretical models of pulsar emission. We propose different scenarios to explain the generation of the torus, based on either incoherent or phase-coherent superposition of orthogonally polarised modes.

14 pages, 11 figures

References in corpus (7)

• PSRCHIVE and PSRFITS An Open Approach to Radio Pulsar Data Storage and Analysis
• Profile and polarization characteristics of energetic pulsars
• The subpulse modulation properties of pulsars at 92 cm and the frequency dependence of subpulse modulation
• Pulsars with NenuFAR: backend and pipelines
• Circular polarization in radio pulsar PSR B1451-68: coherent mode transitions and intrabeam interference
• The Statistics of Radio Astronomical Polarimetry: Disjoint, Superposed, and Composite Samples
• Radio pulsar polarization as a coherent sum of orthogonal proper mode waves

Cited by in corpus (4)

• Pulsar polarization: a partial-coherence model
• Pulsar polarization: a broad-band population view with the Parkes Ultra-Wideband receiver
• Rapid Rotation of Polarization Orientations in PSR B1919+21's Single Pulses: Implications On Pulsar's Magnetospheric Dynamics
• An Introduction to Single-Antenna Radio Astronomical Polarimetry