Magnetospheric eclipses in the double pulsar system PSR J0737-3039

In the binary radio pulsar system PSR J0737-3039, the faster pulsar, A, is eclipsed once per orbit. A clear modulation of these eclipses at the 2.77 s period of pulsar B has recently been discovered. We construct a simple geometric model that successfully reproduces the eclipse light curves, based on the idea that the radio pulses are attenuated by synchrotron absorption on the closed magnetic field lines of pulsar B. The model explains most of the properties of the eclipse: its asymmetric form, the nearly frequency-independent duration, and the modulation of the brightness of pulsar A at both once and twice the rotation frequency of pulsar B in different parts of the eclipse. This detailed agreement confirms the dipolar structure of the star's poloidal magnetic field. The inferred parameters are the inclination angle between the line of sight and orbital plane normal, similar to 90 degrees.5; the inclination of pulsar B's rotation axis to the orbital plane normal, similar to 60 degrees; and the angle between the rotation axis and the magnetic moment, similar to 75 degrees. The model makes clear predictions for the degree of linear polarization of the transmitted radiation. The weak frequency dependence of the eclipse duration implies that the absorbing plasma is relativistic, with a density much larger than the corotation charge density. Such hot, dense plasma can be effectively stored in the outer magnetosphere, where cyclotron cooling is slow. The gradual loss of particles inward through the cooling radius is compensated for by an upward flux driven by a fluctuating component of the current and by the pumping of magnetic helicity on the closed field lines. The trapped particles are heated to relativistic energies by the damping of magnetospheric turbulence and, at a slower rate, by the absorption of the radio emission of the companion pulsar. A heating mechanism is outlined that combines electrostatic acceleration along the magnetic field with the emission and absorption of wiggler radiation by charged particle bunches.