Speaker
Description
Radio-wave emissions originating from pulsar plasmas have been investigated for
decades. Still, there exists a mismatch between the observations and theory. On top of the
polar gap of a neutron star, a plasma cloud is created due to the pair-production process.
Due to the short synchrotron radiation time, only parallel currents, with respect to the
background magnetic field, are present in the plasma cloud. Hence, the cloud can only
sustain emission of the O-mode. The problem arises because the observations are matched to
both O- and X-modes. The production of the X-mode has been studied extensively.
Regardless, the production mechanism remains unknown.
In the nonlinear theory, a current arises. We find two reasons why the nonlinear
current cannot act as a source for the X-mode. Firstly, the current is along the external
magnetic field, meaning that the X-mode is not affected by the current. Secondly, the current
is proportional to an odd power of charge. Hence, in a pair plasma with the same background
distribution for each species, the current vanishes. In other words, the production
mechanism of the X-mode remains a mystery