Study of polarization characteristics of sub-pulse drifting in pulsars.

Decades after their discovery, pulsars continue to intrigue us with the mystery of their emission mechanism. Among the many phenomena in pul- sar radio emissions, subpulse drifting offers unique insights into pulsar beam geometry and emission physics. Subpulse drifting is a phenomenon in which individual substructures within the pulses move in phase across the pulse window, providing insights into the intricate geometry of the pulsar beam. The carousel model (Ruderman & Sutherland 1975) explains subpulse drift- ing as the rotation of sub-beams around the magnetic axis of the pulsar. In this model, sub-beams are formed by sparks near the pulsar surface, rotat- ing around the magnetic axis. However, the model does not account for key observed phenomena, including drift rate variability, mode switching, evo- lutionary drifting, and nulling—the temporary cessation of pulse emission. PSR J0026–1955, rediscovered in the Southern-Sky SMART pulsar survey with the Murchison Widefield Array (MWA) in 2022, is a remarkable source for investigating these phenomena. This pulsar exhibits subpulse drifting, a high nulling fraction (∼ 58%), drift rate evolution, and rapid mode changes, making it an excellent candidate to scrutinize the carousel model. Previ- ous studies (Janagal et al. 2023) identified four distinct subpulse drifting modes, showing both stable and evolutionary subpulse drifting in full in- tensity mode at 300-500 MHz. Using high-sensitivity, full-polarimetric data from the upgraded Giant Meterwave Radio Telescope (uGMRT), we present the first polarization study of the average profile and subpulse drifting be- havior of the pulsar PSR J0026-1955. Our analysis highlights weaker circular compared to linear polarization, with notable polarization angle variations near the pulse peak, hinting at the proof for the rotating vector model. We observe transient evolutionary drifting modes dominating over stable modes, synchronous drift modulation in the polarization angles, and sudden switches in ellipticity angles. Studying the different subpulse drifting modes through the lens of polarization reveals crucial insights into the behavior of sparks near the pulsar surface, shedding light on the underlying mechanisms driving the emission processes and the propagation of the beams, especially in the case of evolutionary subpulse drifting.