Time-dependent magnetohydrodynamic self-similar extragalactic jets

Extragalactic jets are visualized as dynamic erruptive events modelled by time-dependent magnetohydrodynamic (MHD) equations. The jet structure comes through the temporally self-similar solutions in two-dimensional axisymmetric spherical geometry. The two-dimensional magnetic field is solved in the finite plasma pressure regime, or finite $\beta$ regime, and it is described by an equation where plasma pressure plays the role of an eigenvalue. This allows a structure of magnetic lobes in space, among which the polar axis lobe is strongly peaked in intensity and collimated in angular spread comparing to the others. For this reason, the polar lobe overwhelmes the other lobes, and a jet structure arises in the polar direction naturally. Furthermore, within each magnetic lobe in space, there are small secondary regions with closed two-dimensional field lines embedded along this primary lobe. In these embedded magnetic toroids, plasma pressure and mass density are much higher accordingly. These are termed as secondary plasmoids. The magnetic field lines in these secondary plasmoids circle in alternating sequence such that adjacent plasmoids have opposite field lines. In particular, along the polar primary lobe, such periodic plasmoid structure happens to be compatible with radio observations where islands of high radio intensities are mapped

Drift wave turbulence in a dense semiclassical magnetoplasma

A semiclassical nonlinear collisional drift wave model for dense magnetized plasmas is developed and solved numerically. The effects of fluid electron density fluctuations associated with quantum statistical pressure and quantum Bohm force are included, and their influences on the collisional drift wave instability and the resulting fully developed nanoscale drift wave turbulence are discussed. It is found that the quantum effects increase the growth rate of the collisional drift wave instability, and introduce a finite de Broglie length screening on the drift wave turbulent density perturbations. The relevance to nanoscale turbulence in nonuniform dense magnetoplasmas is discussed.Comment: Submitted to Phys. Letters A (2011

Twisted Volkov states in a plasma

This work considers quantum electron states in the field of twisted waves in a plasma. We consider electromagnetic and electrostatic waves. They can be associated with intense laser pulses carrying orbital angular momentum, and to the resulting twisted wakefields. Klein-Gordon and Dirac equations are considered. We show that twisted Volkov states of electrons in electromagnetic and electrostatic waves in a plasma can be excited, and discuss their main properties. These results support the idea that acceleration of helical electron beams in plasmas is possible

Parametric excitation of neutrino pairs by electron plasma waves

The collective coupling of neutrinos and anti-neutrinos in a dense plasma is considered. Such a coupling is provided by the existence of electron plasma waves. These waves can parametrically excite neutrino–anti-neutrino pairs, and the parametric decay rate is established. This stimulated process for neutrino pair production can eventually become dominant over the single particle decay rates characteristic of the usual Urca process and provide an alternative mechanism for the neutrino cooling of collapsing neutron stars

Neutrino-driven instabilities in very dense plasmas

Nonlinear interactions between intense neutrino bursts and electrostatic plasma oscillations in a very dense Fermi plasma are considered. By using the fluid description for intense neutrino bursts and the quantum hydrodynamic model for a dense Fermi plasma, we derive a system of equations that exhibit nonlinear couplings between neutrinos and electrostatic electron plasma waves/ion-acoustic oscillations. The latter incorporate the appropriate electron pressure law and the quantum force involving the strong electron density correlation in a dense Fermi plasma. The governing equations are Fourier transformed and combined to deduce the dispersion relations, which admit instabilities. It is found that for dense Fermi plasmas under extreme conditions, such as those in the interior of massive white dwarfs, the neutrino driven electrostatic instabilities develop rapidly, and they can be responsible for the neutrino energy absorption in dense astrophysical Fermi plasmas