2005ApJ...626L..45D

The pulse profile of pulsar B1822-09 exhibits a very peculiar kind of mode changing: a ``precursor'' appearing just in front of the main pulse (MP) exhibits periods of nulling, during which an interpulse (IP) becomes detectable at a rotation phase separated by roughly 180° from the precursor. We propose that this bizarre phenomenon, which requires an information transfer between the two components, occurs by means of a reversal of the direction of coherent radio emission generated in the same emission region. This interpretation naturally explains the lack of weak radio emission in the off-pulse regions, as well as the problem of information transfer between emission regions associated with the MP precursor and the IP. The reversals also imply nulling. The model has profound physical implications: (1) the mechanism of coherent radio emission must allow radiation into two, opposite, intermittently changing directions; and (2) the radio waves must be able to propagate through inner regions of the neutron star magnetosphere with strong magnetic field. Most importantly, the model implies inward radio emission in the pulsar magnetosphere.