On December 7, at 11:15, we invvite to seminar room (no. 34 in the A2 building).
This time our colleague dr. Andrzej Szary (IA UZ/ASTRON, The Netherlands) will give a talk entitled:
"Polar caps are theme parks. The carousel model of drifting subpulses."
The remarkable drift feature reported for PSR J0815+0939, wherein one component drifts in the direction opposite of the general trend, is a great challenge to pulsar theory.
We proposed a model which breaks with the assumption of carousel rotation of subpulses around the magnetic axis. We showed that since plasma drift takes place in regions where the charge density is below the so-called co-rotational density it should be connected with motion around the rotation axis. The plasma responsible for radio emission is generated and accelerated just above the polar cap, while the radio emission is generated at much higher altitudes. We showed that this transition from the polar cap region to the emission region influences the observed drift characteristics. We performed detailed analysis of archival data of PSR J0815+0939 which revealed that the second component is the only one which exhibits drift in the opposite direction. The bi-drifting phenomenon was modelled by introducing small-scale crust-anchored magnetic anomalies which alter the location of the polar cap with respect to the rotation axis, and hence the drift characteristics.