Interrelation between radio and X-ray signatures of drifting subpulses in pulsars

A partially screened vacuum gap model of the inner acceleration region in pulsars is examined with respect to the drifting subpulse phenomenon and the polar cap heating by the streams of back-flowing particles generated in sparks associated with drifting subpules. We investigated correlation between the intrinsic drift rate and polar cap heating rate and found that they are coupled to each other and therefore the X-ray luminosity Lx from heated polar cap depends only on the observational tertiary subpulse drift periodicity P̂3 (polar cap carousel time). We derived a ”clean-cut” formula relating Lx and P̂3, which manifests the fact that both the drift rate as well as the polar cap heating rate are determined by the same value of the gap electric field. In PSR B0943+10 for which both Lx and P̂3 are known, this formula holds amazingly well. Based on several cases in which P̂3 is known it is argued that Lx/Ė ∼ 10−3, where Ė is the pulsar spin-down rate. This intriguing property was previously attributed to the pulsar magnetospheric emission. In this paper we suggest that it could also be a characteristic property of thermal emission from the spark heated polar cap.