The topology and polarization of sub-beams associated with the 'drifting' subpulse emission of pulsar B0943+10 - III. Analysis of Pushchino 103/40-MHz observations

The rotating emission-beam system of pulsar B0943 + 10 was explored in Paper I of this series using Arecibo observations at 430 and 111 MHz and in Paper II using Gauribidanur 35-MHz data. Here, we have the opportunity to study simultaneous, dual-frequency observations carried out at the Pushchino Radio Astronomy Observatory some 10 yr ago at frequencies of 103 and 40 MHz. The apparent modulation periods (P-3) and circulation times derived from the 11 d of observations seem to fall into two distinct ranges, apparently correlated with profile modal effects. The 103-MHz maps bear a strong resemblance to the 111-MHz Arecibo sequence studied in Paper I, but show a variety of sub-beam intensity patterns, whereas similar comments can be made about the 40-MHz maps in relation to the 35-MHz maps of Paper II. Most interesting here is the result that there is little correspondence between the sub-beam maps at the two frequencies. Only for two of the observations do we find a correspondence between the pairs: one of the 'B'-mode sequences with an asymmetric pattern as well as a 'Q'-mode sequence occurring immediately prior to a transition to the 'B' mode. Finally, we find that our various 'B'-mode observations vary markedly in their profile linear polarization. The strongest sequences suggest differing proportions of secondary polarization mode power.