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We report a study of the transitional intervals between pulsar B0943+10’s two primary Q and B emission modes using Arecibo 327-MHz observations. The goal of this study was to detect signs of a ‘transitional’ mode at 327 MHz, discovered recently at lower frequencies. We have found subpulse drift and profile form patterns at 327 MHz similar to those identified at lower frequencies in the Q-to-B mode transition process. Pulse fading during about 15 stellar rotations preceding the appearance of subpulse drift was observed as well. Another part of the work is devoted to a detailed study of the pulse polarization variations in the main modes. A complex behaviour of the linear polarization percentage (LPP) of the dominant first component of the average profile with B-mode age has been found: during the first 4 h, the LPP continuously increases from 5 to 40 per cent, and over the next 1.5 h gradually decreases down to 30 per cent until the subsequent onset of the Q mode. In contrast, the LPP of the second component does not change over the B-mode lifetime, remaining at the level of 22 per cent. A non-instantaneous decrease in the LPP was detected at Q-mode onset. No systematic change of the LPP of the averaged Q-mode pulses over several hours of age was found. The results are discussed within the framework of the core–cone beam model and orthogonal polarization modes.

We present Faraday rotation measure (RM) values derived at L and P bands as well as some 60 Stokes-parameter profiles, both determined from our long-standing Arecibo dual-frequency pulsar polarimetry programmes. Many of the RM measurements were carried out towards the inner Galaxy and the anticentre on pulsars with no previous determination, while others are remeasurements intended to confirm or improve the accuracy of existing values. Stokes-parameter profiles are displayed for the 58 pulsars for which no meaningful Stokes profile at lower frequency is available and 4 without a high-frequency pair. This is a population that includes many distant pulsars in the inner Galaxy. A number of these polarized pulse profiles exhibit clear interstellar-scattering tails; none the less, we have attempted to interpret the associated emission-beam structures and to provide morphological classifications and geometrical models where possible.

This paper continues our study of radio pulsar emission-beam configurations with the primary intent of extending study to the lowest possible frequencies. Here, we focus on a group of 133 more recently discovered pulsars, most of which were included in the (100–200 MHz) LOFAR High-Band Survey, observed with Arecibo at 1.4 GHz and 327 MHz, and some observed at decametre wavelengths. Our analysis framework is the core/double-cone beam model, and we took opportunity to apply it as widely as possible, both conceptually and quantitatively, while highlighting situations where modelling is difficult, or where its premises may be violated. In the great majority of pulsars, beam forms consistent with the core/double-cone model were identified. Moreover, we found that each pulsar’s beam structure remained largely constant over the frequency range available; where profile variations were observed, they were attributable to different component spectra and in some instances to varying conal beam sizes. As an Arecibo population, many or most of the objects tend to fall in the Galactic anticenter region and/or at high Galactic latitudes, so overall it includes a number of nearer, older pulsars. We found a number of interesting or unusual characteristics in some of the pulsars that would benefit from additional study. The scattering levels encountered for this group are low to moderate, apart from a few pulsars lying in directions more towards the inner Galaxy.

This paper provides analyses of the emission beam structure of 76 ‘B’-named pulsars within the Arecibo sky. Most of these objects are included in both the Gould & Lyne and LOFAR High Band surveys and thus complement our other works treating various parts of these populations. These comprise a further group of mostly well-studied pulsars within the Arecibo sky that we here treat similarly to those in Olszanski et al. – and extend our overall efforts to study all of the pulsars in both surveys. The analyses are based on observations made with the Arecibo Telescope at 327 MHz and 1.4 GHz. Many have been observed at frequencies down to 100 MHz using either LOFAR or the Pushchino Radio Astronomy Observatory as well as a few with the Long Wavelength Array at lower frequencies. This work uses the Arecibo observations as a foundation for interpreting the low frequency profiles and emission-beam geometries. We attempt to build quantitative geometric emission-beam models using the core/double-cone topology, while reviewing the evidence of previous studies and arguments for previous classifications on these sources. These efforts were successful for all but two pulsars, and interesting new subpulse modulation patterns were identified in a number of the objects. We interpret the Arecibo pulsar population in the context of the entire population of ‘B’ pulsars.

We present pulsar emission beam analyses and models in an effort to examine pulsar geometry and physics at the lowest frequencies scattering permits. We consider two populations of well-studied pulsars that lie outside the Arecibo sky, the first drawing on the Jodrell Bank Gould & Lyne survey down to –35° declination and a second using Parkes surveys in the far south. These assemble the full sky population of 487 pulsars known before the late 1990s which conveniently all have ‘B’ names. We make full use of the core/double-cone emission beam model to assess its efficacy at lower frequencies, and we outline how different pair plasma sources probably underlie its validity. The analysis shows that with a very few exceptions pulsar radio emission beams can be modeled quantitatively with two concentric conal beams and a core beam of regular angular dimensions at 1 GHz. Further, the beamforms at lower frequencies change progressively in size but not in configuration. Pulsar emission-beam properties divide strongly depending on whether the plasma excitation is central within the polar fluxtube producing a core beam or peripheral along the edges generating conal beams, and this seems largely determined by whether their spin-down energy is greater or less than about 1032.5 ergs s−1. Core emission dominated pulsars tend concentrate closely along the Galactic plane and in the direction of the Galactic center; whereas conal pulsars are somewhat more uniformly distributed both in Galactic longitude and latitude. Core dominated pulsars also tend to be more distant and particularly so in the inner Galaxy region.

We present radio pulsar emission beam analyses and models with the primary intent of examining pulsar beam geometry and physics over the broadest band of radio frequencies reasonably obtainable. We consider a set of well-studied pulsars that lie within the Arecibo sky. These pulsars stand out for the broad frequency range over which emission is detectable, and have been extensively observed at frequencies up to 4.5 GHz and down to below 100 MHz. We utilize published profiles to quantify a more complete picture of the frequency evolution of these pulsars using the core/double-cone emission beam model as our classification framework. For the low-frequency observations, we take into account measured scattering time-scales to infer intrinsic versus scatter broadening of the pulse profile. Lastly, we discuss the populational trends of the core/conal class profiles with respect to intrinsic parameters. We demonstrate that for this subpopulation of pulsars, core and conal dominated profiles cluster together into two roughly segregated $P{\!-\!}\dot{P}$ populations, lending credence to the proposal that an evolution in the pair-formation geometries is responsible for core/conal emission and other emission effects such as nulling and mode changing.