The topology and polarisation of subbeams associated with the “drifting” subpulse emission of pulsar B0943+10

IV. Q-to-B-mode recovery dynamics

¹ Sterrenkundig Instituut “Anton Pannekoek”, 1098 SJ Amsterdam, The Netherlands e-mail: jrankin@astro.uva.nl
² Pushchino Radio Astronomy Observatory, 142292 Pushchino, Russia e-mail: suleym@prao.psn.ru
³ Isaac Newton Institute of Chile, Pushchino Branch, Russia

Received: 1 September 2005
Accepted: 20 March 2006

Abstract

Pulsar B0943+10 is well known for its “B” (burst) mode, characterized by accurately drifting subpulses, in contrast to its chaotic “Q” (quiet) mode. Six new Arecibo observations at 327 MHz with durations of 2+ h each have shed considerable light on the modal dynamics of this pulsar. Of these, three were found to be exclusively “B” mode, and three were discovered to exhibit transitions from the “Q” to the “B” mode. One of these observations has permitted us to determine the circulation time of the subbeam carousel in the “Q” mode for the first time, at some  stellar rotation periods. The onset of the “B” mode is then observed to commence similarly in all three observations. The initial circulation time is about 36 periods and relaxes to nearly 38 periods in a roughly exponential fashion with a characteristic time of some 1.2 h. This is the longest characteristic time ever found in a mode-switching pulsar. Moreover, just after the “B”-mode onset the pulsar exhibits a symmetrical resolved-double profile form with a somewhat stronger trailing component, but this second component slowly dies away leaving the usual single “B”-mode profile with the longitude of the magnetic axis falling at about its trailing half power point. Thus it would appear that Q-to-B- and B-to-Q-transitions have different characteristic times. Some speculations are given on the nature of this slow modal alternation.