Mode switching is an emission phenomenon in which the mean pulse profile abruptly switches between two or more stable states. Changes in current flow in the inner acceleration region or pulsar magnetosphere geometry can, in theory, result in mode switching.
Dr. Sun Shengnan of the Chinese Academy of Sciences’ (CAS) Xinjiang Astronomical Observatory (XAO) and her colleagues discovered that different states of emissions can be generated in different regions of the pulsar magnetosphere by analysing the polarisation of PSR J0614+2229 and PSR J1938+2213 using FAST observations.
The Astrophysical Journal published related findings.
PSR J0614+2229 was discovered to have two distinct emission modes, according to the researchers. The position angle (PA) swings of the two modes differed, implying that emission height may vary between modes. By rotating vector model fitting, they discovered that the difference in emission heights between the two modes was 90 km.
PSR J0614+2229 became much brighter during the transition between modes, which had never been seen before in mode-changing pulsars. The brighter emissions during mode switching could be related to the triggering mechanism of changing modes.
Furthermore, the PSR J1938+2213 appeared to have a weak emission state superimposed on brighter burst emissions, with the weak state always present. The PA swings of the two states differed noticeably, and the burst state displayed a sudden 90° jump, known as the orthogonal polarisation mode (OPM) phenomenon. The OPM can only be seen in the burst state, not in both.
The findings imply that emissions of two states are produced in different regions of the pulsar magnetosphere.