2020PASP..132c4201R

The braking index parameter of intermittent pulsar would provide important insight into the pulsar slowdown and emission mechanism. In previous work, we presented the first braking index n=ν1/{dot}ν² of the intermittent pulsar B1931+24, J1841-0500, J1832+0029 and nulling pulsar B0823+26, by using their observed spin frequency first derivatives {dot}ν in "on" and "off" states. In this paper, to improve and justify our method for studying the braking mechanism of intermittent pulsars, we continue to formulate a method in which the second braking indices, m=ν²ν/{dot}ν³, of these pulsars can also be given with only the observed spin frequency first derivatives {dot}ν_on and {dot}ν_off. This paper will discuss, according to the emission and spin-down property of intermittent pulsars, three different magnetospheric configuration changes in the polar cap region. We find our approach produces feasible values of the second braking index of intermittent pulsar. Our calculations of the second braking indices are in close agreement with predicted second braking indices m = n(2n - 1), which are given by simple spin-down law of pulsar spin evolution, resulting in indirect observational support to our model.