PSR B0809+74: Understanding Its Perplexing Subpulse-separation (P2)   Variations
  The longitude separation between adjacent drifting subpulses, $P_2$, is roughly constant for many pulsars. It was then perplexing when pulsar B0809+74 was found to exhibit substantial variations in this measure, both with wavelength and with longitude position within the pulse window. We analyze these variations between 40 and 1400 MHz, and we show that they stem primarily from the incoherent superposition of the two orthogonal modes of polarization. 
Joanna M. Rankin (UVM), R. Ramachandran (Berkeley), Svetlana A.   Suleymanova (PRAO)