Abstract The well known drifter PSR B0031-07 is known to exhibit drifting sub-pulses where the spacing between the drift bands (P3) shows three distinct modes A, B and C corresponding to 13, 7 and 4 times the pulsar period, respectively. We have investigated periodicities and polarisation properties of PSR B0031-07 for a sequence of 2700 single pulses taken simultaneously at 328 MHz and 4.85 GHz. We found that mode A occurs simultaneously at these frequencies, while modes B and C only occur at 328 MHz. However, when the pulsar is emitting in mode B at the lower frequency there is still emission at the higher frequency, hinting towards the presence of mode B emission at a weaker level. Further, we have established that modes A and B are associated with two orthogonal modes of polarisation, respectively. Based on these observations, we suggest a geometrical model where modes A and B at a given frequency are emitted in two concentric rings around the magnetic axis with mode B being nested inside mode A.
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