We report analysis of an 8-h observation of PSR B0943+10 at 325 MHz performed at the Giant Metrewave Radio Telescope (GMRT) in India. B0943+10 is well known for displaying regular subpulse drifting and two emission modes. We investigate the modal behaviour of B0943+10. By reconstructing an entire ‘B’ mode from two consecutive ‘B’ modes, we estimate that the pulsar spends roughly 7.5 h in the ‘B’ mode and about 2.2 h in the ‘Q’ mode, on average. Although the pulsar can switch modes within one pulse, the subpulse drift rate changes with a characteristic time of 1.2 h over the course of a ‘B’...

We report analysis of an 8-h observation of PSR B0943+10 at 325 MHz performed at the Giant Metrewave Radio Telescope (GMRT) in India. B0943+10 is well known for displaying regular subpulse drifting and two emission modes. We investigate the modal behaviour of B0943+10. By reconstructing an entire ‘B’ mode from two consecutive ‘B’ modes, we estimate that the pulsar spends roughly 7.5 h in the ‘B’ mode and about 2.2 h in the ‘Q’ mode, on average. Although the pulsar can switch modes within one pulse, the subpulse drift rate changes with a characteristic time of 1.2 h over the course of a ‘B’ mode. Under the subbeam carousel model we find the drift rate changes are produced by a 10 per cent increase in the average number of subbeams and a 16 per cent increase in the carousel circulation time. We speculate that under the partially screened gap model the increase in circulation time should be related to a small increase in the neutron star surface temperature.