arXiv subjects

Fabrice Mottez

Publications and source records attributed to Fabrice Mottez.

23 records · Page 2Linked to original sources

arXiv2011

On the possibility of radio emission of planets around pulsars

A planet orbiting around a pulsar would be immersed in an ultra-relativistic under-dense plasma flow. It would behave as a unipolar inductor, with a significant potential drop along the planet. As for Io in Jupiter's magnetosphere, there would be two stationary Alfvén waves, the Alfvén wings (AW), attached to the planet. The AW would be supported by strong electric currents, in some circumstances comparable to those of a pulsar. It would be a cause of powerful radio waves emitted all along the AW, and highly collimated through relativistic aberration. There would be a chance to detect these radio-emissions from Earth. The emission would be pulses as for ordinary pulsars; their occurrence would depend on the planet-star-observer angle. These results are still preliminary, further work needs to be done.

astro-ph.EP↗

arXiv2011

Magnetic coupling of planets and small bodies with a pulsar wind"

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, such as PSR B1257+12 and PSR B1620-26 that are expected to hold a planetary system, or to pulsars with suspected asteroids or comets. We extend the theory of Alfvén wings to relativistic winds. When the wind is relativistic albeit 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" one second pulsar, the associated current can reach the same magnitude as the Goldreich-Julian current that powers the pulsar's magnetosphere.

astro-ph.EP↗

arXiv2011

A magnetic thrust action on small bodies orbiting a pulsar

We investigate the electromagnetic interaction of a relativistic stellar wind with small bodies in orbit around the star. Based on our work on the theory of Alfvén wings to relativistic winds presented in a companion paper, we estimate the force exerted by the associated current system on orbiting bodies and evaluate the resulting orbital drift. This Alfvénic structure is found to have no significant influence on planets or smaller bodies orbiting a millisecond pulsar. %influence on the orbit of bodies around a millisecond pulsar. On the timescale of millions of years, it can however affect the orbit of bodies with a diameter of 100 kilometres around standard pulsars with a period $P \sim $1 s and a magnetic field $B \sim 10^{8}$ T. Kilometer-sized bodies experience drastic orbital changes on a timescale of $10^4$ years.

astro-ph.EP↗

arXiv2006

Comment on "PIC simulations of circularly polarised Alfvén wave phase mixing: A new mechanism for electron acceleration in collisionless plasmas" by Tsiklauri et al

Tsiklauri et al. recently published a theoretical model of electron acceleration by Alfvén waves in a nonuniform collisionless plasmas. We compare their work with a series of results published earlier by an another team, of which Tsiklauri et al. were probably unaware. We show that these two series of works, apparently conducted independently, lead to the same conclusions. This reinforces the theoretical consistency of the model.

astro-ph↗

arXiv2004

Exact nonlinear analytic Vlasov-Maxwell tangential equilibria with arbitrary density and temperature profiles

The tangential layers are characterized by a bulk plasma velocity and a magnetic field that are perpendicular to the gradient direction. They have been extensively described in the frame of the Magneto-Hydro-Dynamic (MHD) theory. But the MHD theory does not look inside the transition region if the transition has a size of a few ion gyroradii. A series of kinetic tangential equilibria, valid for a collisionless plasma is presented. These equilibria are exact analytical solutions of the Maxwell-Vlasov equations. The particle distribution functions are sums of an infinite number of elementary functions parametrized by a vector potential. Examples of equilibria relevant to space plasmas are shown. A model for the deep and sharp density depletions observed in the auroral zone of the Earth is proposed. Tangential equilibria are also relevant for the study of planetary environments and of remote astrophysical plasmas.

physics.space-ph↗