Magnetic coupling of planets and small bodies with a pulsar wind

Abstract

Aims. We investigate the electromagnetic interaction of a relativistic stellar wind with a planet or a smaller body in orbit around the star. This may be relevant to objects orbiting a pulsar that are expected to hold a planetary system, such as PSR B1257+12 and PSR B1620-26, or to pulsars with suspected asteroids or comets. Methods. We extend the theory of Alfvén wings to relativistic winds. Results. When the wind is relativistic but slower than the total Alfvén speed, a system of electric currents carried by a stationary Alfvénic structure is driven by the planet or by its surroundings. For an Earth-like planet around a "standard" second pulsar, the associated current can reach the same magnitude as the Goldreich-Julian current that powers the pulsar's magnetosphere.

Towards a theory of extremely intermittent pulsars

“…The factor Σ A is the Alfvén wing conductance. Mottez & Heyvaerts (2011b) have shown that for a highly relativistic Poynting-flux-dominated wind, as expected around pulsars,…”

“…Mottez & Heyvaerts (2011b) have shown than in cold ideal magneto-hydrodynamic Poyntingflux-dominated winds, where the models show that asymptotically γ ∞ ∼ σ 1/3 0 , the wind is sub-Aflvénic, in the sense defined above, at any distance. But if γ ∞ ∼ σ a 0 , and a > 1/3, a transition from sub-Alfvénic to super-Alfvénic wind occurs at a finite distance.…”

“…In the highly relativistic pulsar wind, the acceleration and emission process may be quite different from those arising in the vicinity of Jupiter, but the current A125, page 3 of 8 A&A 555, A125 (2013) neutron star I A certainly constitutes an important source of free energy for radio emissions. Mottez & Heyvaerts (2011b) have suggested that the strong current in the pulsar companion's Alfvén wings could be unstable and might cause powerful radio emissions. The generation mechanism of these emissions has not been studied yet, but preliminary results are presented in Mottez (2011), assuming that the radio-source is convected with the pulsar's wind when it passes the Alfvén wing.…”

“…Neubauer (1980) has developed a non-relativistic model of Alfvén wings to explain the interaction between Jupiter and its satellite Io. Mottez & Heyvaerts (2011b) have adapted a linear but relativistic version of that theory. The geometry of an Alfvén wing is sketched in Fig.…”

“…Taking Eqs. (3) and (5) into account, the definition of the induced electric field E 0 and the fact that at a large distance from the light cylinder v φ Ωr, the electric current carried by an Alfvén wing is, for the best energy coupling of the planet and the Alfvén wing (Mottez & Heyvaerts 2011b)…”