Mattias Marklund

Nonlinear model for magnetosonic shocklets in plasmas

Exact nonlinear equations for magnetosonic shocklets in a uniform hot magnetoplasma are derived by using the nonlinear magnetohydrodynamic equations. Analytic, as well as numerical, solutions of the nonlinear equations are presented. Shocklike structures of the ion fluid velocity and magnetic field (or the plasma density) perturbations are obtained. The results may have relevance to the understanding of fast magnetosonic shocklets that have been recently observed by onboard instruments of the Cluster spacecraft at the Earth’s bow shock.

Nonlinear effects associated with interactions of intense photons with a photon gas

The derivative correction to the Heisenberg–Euler Lagrangian has been introduced. A general dispersion relation for a photon traveling on a slowly varying background electromagnetic field has been presented. A set of equations describing the nonlinear propagation of an electromagnetic pulse on a radiation fluid background is then derived. Novel modulational and filamentational instabilities are found, and using numerical methods, it has been shown that electromagnetic pulses may collapse and split into pulse trains. Also presented are analytical results concerning the collapse, split, and Mach cone formation. The implications of the results are discussed.

Nonlinear propagation of broadband intense electromagnetic waves in an electron-positron plasma

A kinetic equation describing the nonlinear evolution of intense electromagnetic pulses in electron-positron (e-p) plasmas is presented. The modulational instability is analyzed for a relativistically intense partially coherent pulse, and it is found that the modulational instability is inhibited by the spectral pulse broadening. A numerical study for the one-dimensional kinetic photon equation is presented. Computer simulations reveal a Fermi-Pasta-Ulam-type recurrence phenomenon for localized broadband pulses. The results should be of importance in understanding the nonlinear propagation of broadband intense electromagnetic pulses in e-p plasmas in laser-plasma systems as well as in astrophysical plasma settings.

Dust acoustic wave in a strongly magnetized pair-dust plasma

The existence of the dust acoustic wave (DAW) in a strongly magnetized electron-positron (pair)-dust plasma is demonstrated. In the DAW, the restoring force comes from the pressure of inertialess electrons and positrons, and the dust mass provides the inertia. The waves could be of interest in astrophysical settings such as the supernovae and pulsars, as well as in cluster explosions by intense laser beams in laboratory plasmas.

Kinetic theory of electromagnetic ion waves in relativistic plasmas

A kinetic theory for electromagnetic ion waves in a cold relativistic plasma is derived. The kinetic equation for the broadband electromagnetic ion waves is coupled to the slow density response via an acoustic equation driven by a ponderomotive force-like term linear in the electromagnetic field amplitude. The modulational instability growth rate is derived for an arbitrary spectrum of waves. The monochromatic and random phase cases are studied.

The intense radiation gas

We present a new dispersion relation for photons that are nonlinearly interacting with a radiation gas of arbitrary intensity due to photon-photon scattering. It is found that the photon phase velocity decreases with increasing radiation intensity, and it attains a minimum value in the limit of super-intense fields. By using Hamiltons ray equations, a self-consistent kinetic theory for interacting photons is formulated. The interaction between an electromagnetic pulse and the radiation gas is shown to produce pulse self-compression and nonlinear saturation. Implications of our new results are discussed.

Relativistic self-compression approaching the Schwinger limit

The effects of relativistic mass increase is considered in the context of intense laser-plasma interactions. It is found that the result of the relativistic effect is to enhance the self-compression and collapse of the intense laser pulse, making it possible to reach the Schwinger field limit, at which pair creation would need to be considered.

Random phases in Bose-Einstein condensates with higher order nonlinearities

Abstract.We present a statistical description of Bose-Einstein condensates with general higher order nnonlinearities. In particular, we investigate the case of cubic-quintic nonlinearities,nof particular interest for dilute condensates. nThe implication of decoherence for the stability properties of the ncondensate is discussed. nn

Statistical description of short pulses in long optical fibers: effects of nonlocality

We present a statistical description of the propagation of short pulses in long optical fibers, taking into account the Kerr and nonlocal nonlinearities on an equal footing. We use the Wigner approach on the modified nonlinear Schrödinger equation to obtain a wave kinetic equation and a nonlinear dispersion relation. The latter shows that the optical pulse decoherence reduces the growth rate of the modulational instability and thereby contributes to the nonlinear stability of the pulses in long optical fibers. It is also found that the interaction between spectral broadening and nonlocality tends to extend the instability region.