In a recent work on variations in pulsar emission properties, Dr. Rai Yuen from the Xinjiang Astronomical Observatory, CAS, generalises the uniqueness of the radio profile of a pulsar to one specific emission configuration state in the magnetosphere of the pulsar. A pulsar may contain more than one emission configuration state allowing multiple profiles, each of a unique shape, to exist and changes in profile shape through switching between different states. 

Pulsar radio profiles are generated from averaging over large amount of individual pulses that arrive at a telescope as a steady steam of signals. Individual pulses from a pulsar change greatly but the average profile is stable over a long time and unique to the pulsar. No two average profiles are exactly the same allowing such feature to be used as fingerprints for pulsars.  

Occasionally, the average profiles of some pulsars suddenly change between two or more different shapes within a few pulsar rotations. A phenomenon known as mode-changing. Recent observations revealed another kind of profile change that takes place over longer timescales. Both phenomena are difficult to understand under the framework of an unchanging pulsar magnetosphere.

By abandoning the unchanging assumption, a pulsar magnetosphere may consist of multiple different emission configuration states each with its own characteristics for radio emission production. It is then possible to show that a profile shape is correlated to an emission state and that changes in the profile are due to switching between different states. The profile shape is unique only to an emission configuration state and it changes if the pulsar changes from one configuration to another different configuration in the magnetosphere as shown in Figure 1.

The proposal of multiple configuration states suggests that at least two emission mechanisms of different properties are in function, each at different epochs, in pulsar magnetospheres. It remains uncertain as to how many different emission configuration states can exist in a pulsar magnetosphere, and the mechanism responsible for switching between different states is still unknown. However, the model presents an alternative to understanding of the variability of pulsar radio emission.

Figure 1: Simulation showing two profiles in black and blue each corresponds to a different emission configuration. The profile appears to shift from one position (black) to another (blue), and vice versa, as the emission state switches between two different configurations. 

For further information please contact:

Rai Yuen

Tel: 0991-3689017

Email: ryuen@xao.ac.cn

Publication: Yuen, R., Melrose, D. B.: 2017, MNRAS, 469, 2049