MeerKAT observations of the reversing drifting subpulses in PSR J1750-3503

Abstract: We present an analysis of the subpulse drift in PSR J1750-3503, which is characterized by abrupt transitions of drift direction. As the pulsar does not exhibit other mode changes or clear nulling, it is an ideal candidate system for studying the phenomenon of drift direction change. For $\sim 80\%$ of the time the subpulses are characterized by positive drift - from early to later longitudes - while the drift direction is negative in the other $\sim 20\%$. The subpulse separation for single pulses with positive drift, $P_2=(18.8\pm 0.1)^{\circ}$, is higher then for single pulses with negative drift, $P_2=(17.5\pm 0.2)^{\circ}$. When the drift is stable, the measured repetition time of the drift pattern is $P_3^{\rm obs}=(43.5 \pm 0.4) P$, where $P$ is pulsar period. We show that the observed data can be reproduced by a carousel models with subpulse rotation around the magnetic axis using purely dipolar configuration of surface magnetic field. The observed drift characteristics can be modeled assuming that the actual repetition time $P_3<2P$, such that we observe its aliased value. A small variation in $P_3$, of the order of $6\%$ (or less assuming higher alias orders), is enough to reproduce the characteristic drift direction changes we observe.