Multifrequency Study on The Mode Switching of PSR J0614+2229

The mode switching phenomenon of PSR J0614+2229 was studied by using the archived observations at 686 MHz, 1369 MHz and 3100 MHz with the Parkes radio telescope which have not been published before, and combining existing observations from the literature. Over a wide frequency range from 327~MHz to 3100~MHz, the pulsar switches between one mode occurring earlier in pulse phase (mode A) and the other mode appearing later in phase (mode B), with a generally stable phase offset between their profile peaks. The two modes are found to be different in the following aspects. (1) Mode A has a flatter spectrum than mode B does, with a difference in the spectral index about 0.5. This accounts for the phenomenon that the flux ratio between the modes A and B increases with frequency and mode A becomes stronger than mode B above $sim500$ MHz. (2) For mode B, the flux density of the sub-integrated profile is anti-correlated with the emission phase, indicating that the emission from earlier phases is relatively stronger than that from later phases. But such an anti-correlation is not observed in mode A. (3) The frequency dependence of the full width of half maximum (FWHM) of the two modes are opposite to each other, namely the FWHM of mode A increases with frequency, while that of mode B decreases with frequency. A possible interpretation is suggested that the longitudinal spectral variation across the two beams may be opposite to each other. In mode A, the spectrum should steepen from the edge to the center of the beam. When the emission switches to mode B, the spectral variation should be reversed....