Coherent pulsar radio radiation by antenna mechanisms: general theory

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Abstract
We apply our general formalism for coherent curvature radiationto the radio emission of pulsars. We adopt the magnetospheric model of Ruderman & Sutherland. The electrostatic streaming instability dominates all other plasma modes. The beam–plasma instability they envisioned does not grow rapidly enough to produce appreciable coherence, and thus cannot explain the observed radiation. Nonetheless, we derive an expression for pulsar luminosity, |$L(\nu)\,\propto\,\nu^{-2.2}$|⁠, with features which should be shared by a general class of simple, instability-driven radiation models. The electrostatic instabilities make the electron–positron plasma into a phased array, like an antenna. This proves much more efficient than the usual, local picture of coherence which extends only over one wavelength. We also conjecture that the high-frequency steepening of L(ν) derives from linear growth near the pulsar, and that the low-frequency turnover may arise when relativistic plasma energy density exceeds the dipolar field energy density, rather than from self-absorption. In Tables 1 and 2 we give convenient conversions from observed radiation properties to pulsar parameters in hopes that these will prove useful to observers.

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