It is with great pleasure that I write this modest and very personal tribute for the current volume of the Journal of Plasma Physics dedicated to honor Professor José Tito da Luz Mendonça on the occasion of his 65th birthday. Modest because, most probably, I will not have enough expertise to summarize an outstanding and truly impressive career of more than 40 years in a short text. Very personal since this contribution is based on my knowledge acquired during more than 25 years of joint work at Instituto Superior Técnico (IST).

We present a dispersion relation for a plane-polarized electromagnetic wave in plasmas composed of cold electrons, relativistically hot electrons and bi-Maxwellian protons. It is shown that the free energy in proton-temperature anisotropy drives purely growing electromagnetic modes in our three-component plasma. Expressions for the growth rates and thresholds of instabilities are presented. The present results are relevant for explaining the origin of spontaneously generated magnetic fields in laboratory and astrophysical plasmas.

It is our great pleasure to dedicate this special issue of Journal of Plasma Physics to our dear friend and colleague Professor Padma Kant Shukla on the occasion of his 60th birthday on 7th July 2010. Padma is one of the most prominent and productive scientists in plasma physics and in neighboring fields, and has published more than 1300 papers in scientific journals. It has for some time been the aim of his friends to honor him on this occasion, and earlier this year we sent out invitations to distinguished scientists who have collaborated with Padma over the years. The response has been overwhelming, and we collected 43 manuscripts, covering a diverse range of topics in plasma physics, which are now published in this issue. We believe that these papers reflect some of the impact of Padma's research in plasma physics.

The amplitude modulation of a finite amplitude drift wave by zonal flows in a non-uniform magnetoplasma is considered. The evolution of a nonlinearly coupled drift wave-zonal flow (DW-ZF) system is governed by a nonlinear equation for the slowly varying envelope of the drift waves, which drives (via the Reynolds stress of the drift wave envelope) the second equation for zonal flows. The nonlinear dispersion relation for the modulational instability of a drift wave pump is derived and analyzed. In a special case, the DW-ZF system of equations reduces to the cubic nonlinear Schrödinger equation, which admits localized solutions in the form of DW envelope solitons, accompanied by a shock-like ZF structure. Numerical solutions of the nonlinearly coupled DW-ZF systems reveal that an arbitrary spatial distribution of the DW rapidly decays into an array of localized drift wave structures, propagating with different speeds, that are robust and, in many respect, behave as solitons. The corresponding ZF evolves into the sequence of shocks that produces a strong shearing, i.e. multiple plasma flows in alternating directions.

In this letter, we propose a model to explain the disintegration of extragalactic jets and to predict the associated timescale. The model assumes that a jet is current and charge neutral as well as collimated at its source; however, the forward electron current gradually decays producing a magnetic field transverse to the direction of jet propagation. This growing transverse magnetic field eventually causes the jet to disintegrate.

We present a derivation of the dispersion relation for electrostatic oscillations in a zero-temperature quantum plasma, in which degenerate electrons are governed by the Wigner equation, while non-degenerate ions follow the classical fluid equations. The Poisson equation determines the electrostatic wave potential. We consider parameters ranging from semiconductor plasmas to metallic plasmas and electron densities of compressed matter such as in laser compression schemes and dense astrophysical objects. Owing to the wave diffraction caused by overlapping electron wave function because of the Heisenberg uncertainty principle in dense plasmas, we have the possibility of Landau damping of the high-frequency electron plasma oscillations at large enough wavenumbers. The exact dispersion relations for the electron plasma oscillations are solved numerically and compared with the ones obtained by using approximate formulas for the electron susceptibility in the high- and low-frequency cases.

It is a great honor and pleasure to dedicate this special issue of Journal of Plasma Physics to our dear friend and colleague Professor Tito Mendonça on the occasion of his 65th birthday on December 28, 2010. Professor Tito is one of the most inspiring scientists in plasma physics, with contributions touching many other fields, using cross-cutting methodologies and novel theoretical techniques, which have led to important contributions and insights. Moreover, he has inspired many students at the Instituto Superior Técnico in Lisbon and mentored a new generation of physicists in Portugal to pursue scientific careers in a wide spectrum of fields from plasma physics to nonlinear optics, from astrophysics to quantum optics.

The potential distribution around a charged dust grain in an electronegative plasma is obtained by using the appropriate dielectric susceptibilities for the Boltzmann distributed electrons and negative ions, and for the inertial positive ions that are streaming from the bulk plasma into the electronegative plasma sheath. The existence of oscillatory ion wakefields is shown. Positive ions are trapped/focused in the ion wakefields, and subsequently the negative dust particles are attracted to each other, forming ordered dust structures.

The solar coronal plasma is maintained at temperatures of millions of degrees, much hotter than the photosphere, which is at a temperature of just 6000 K. In this paper, the plasma particle heating based on the kinetic theory of wave–particle interactions involving kinetic Alfvén waves and lower-hybrid drift modes is presented. The solar coronal plasma is collisionless and therefore the heating must rely on turbulent wave heating models, such as lower-hybrid drift models at reconnection sites or the kinetic Alfvén waves. These turbulent wave modes are created by a variety of instabilities driven from below. The transition region at altitudes of about 2000 km is an important boundary chromosphere, since it separates the collision-dominated photosphere/chromosphere and the collisionless corona. The collisionless plasma of the corona is ideal for supporting kinetic wave–plasma interactions. Wave–particle interactions lead to anisotropic non-Maxwellian plasma distribution functions, which may be investigated by using spectral analysis procedures being developed at the present time.

As the Journal of Plasma Physics so fittingly dedicates this current volume to honor Professor Padma Kant Shukla, for his extraordinary and prolific contributions to the field, over a period spanning four decades, on the occasion of his 60th birthday, it gives me great pleasure to contribute this personal tribute. Padma is without doubt one of the preeminent plasma theorists of his generation with a productivity that is phenomenal and perhaps unmatched (well in excess of 1000). What is truly impressive is not only his extraordinary productivity but also the depth and breadth of his contributions, which while being centered in plasma physics, bridge many other disciplines including condensed matter physics, particle physics, and geophysics. Although I was familiar with Padma's work, in several areas, earlier, I first met him about 20 years ago, when he began working in a field of great interest to me, namely dusty plasmas. Very quickly Padma became a leader in this very new and rapidly developing field, in particular, pioneering the fascinating area of waves in dusty plasmas; predicting the existence, among others, of the very low frequency dust acoustic mode, which was spectacularly observed subsequently in the laboratory, and has been cited about 1000 times since. During this time I got to know Padma very well while participating in numerous international meetings convened by him and also while hosting him, several times, as a visiting professor at my home institution, and observing his multifaceted talents as an outstanding scholar, inspiring mentor, tireless organizer, and committed humanitarian. While Padma's accomplishments are extraordinary, what makes them even more noteworthy is his personal history. Padma came from a family of modest means in a small Indian village. He was the first member of his extended family who went to college, mainly due to the efforts of the village schoolteacher who obviously recognized the young student's innate talent. Living up to his schoolteacher's expectations he later graduated (with honors) from Agra University at the age of 17 and then proceeded to obtain his PhD in physics from the Hindu Banaras University, at the age of 21. He then proceeded to the University of Umeå, Sweden, on scholarship, and quickly blossomed to his full potential under the caring guidance of Prof. Lennart Stenflo, while also earning his second PhD, three years later. These early experiences deeply influenced Padma; on the one hand he recognizes that raw talent exists in all corners of the world, and on the other hand he feels a deep commitment to help discover, nurture, and mentor such talent. Toward this end Padma did several things. He organized numerous international meetings in both developed and developing nations. He has also continued to organize the annual Plasma Physics Summer School at the Abdus Salam International Center for Theoretical Physics in Trieste, Italy. He has used these opportunities to discover promising young scientists from the world over, helping them to come to his host university in Bochum, with support obtained from various international organizations, and mentored them. These young scholars, haling from every continent of the world, have gone on to become active scientists in their own right and many have proceeded to become leading researchers, educators, and administrators in their home countries. It is in recognition of his “extraordinary efforts in the discovery, the nurturing and mentoring of scientific talent across the globe” that he received the highly prestigious Nicholson Medal, awarded by the American Physical Society, for human outreach by a leading scientist in 2005. In recognition of his outstanding scientific contributions Padma has received numerous international honors including several honorary doctorates, foreign membership of several national academies, fellowships of a number of international scientific organizations and prizes. Yet, I think that among all these honors, the Nicholson Medal perhaps is the most appropriate because it recognizes what Padma truly is: not just a great scientist but one who is also an outstanding humanitarian. It has been a great privilege to have known Padma for the last twenty years. I have been inspired by his life and his work. Personally, as well as on behalf of all his friends and admirers in the scientific community around the globe, I wish Padma a long, happy, healthy, and prosperous life, with continuing success in all his endeavors.

It is shown that the ponderomotive force of a large-amplitude electromagnetic wave in Rydberg plasmas can generate quasi-stationary magnetic fields. The present result can account for the origin of seed magnetic fields in the ultracold Rydberg plasmas when they are irradiated by the high-frequency electromagnetic wave.

Relativistic collisional effects on the filamentation instability are analytically and numerically investigated by comparing collisionless and collisional scenarios for a fast ignition (FI) configuration. The theoretical kinetic model, including warm species and space charge effects, predicts the preferential formation of larger filaments and the inhibition/enhancement of the instability when collisions are accounted for. These collisional effects are qualitatively and quantitatively confirmed by 1D and 2D particle-in-cell (PIC) simulations, also providing a physical picture for the inhibition/enhancement regime due to collisions, based on the electron beam slowdown. By plugging typical FI parameters in the dispersion relation, the theoretical model predicts significant growth rates of the instability deep inside the FI target, thus showing the potential role of the filamentation instability as a mechanism for energy deposition into the pellet core.

Some previous dispersion relations for large amplitude waves in plasmas are generalized so that also quantum effects are included.

The authors have considered the charging of spherical particles in a plasma, taking into account the electric field emission of electrons from the dust particles and the change in the electron/ion densities in the plasma. The dependence of the charge of a particle and electron/ion densities on the radius and number of dust particles and the density of electrons/ions and the temperature in the undisturbed plasma has been studied numerically without and with the inclusion of the electric field emission of electrons from the particles. It is seen that both the electric field emission and the electron/ion kinetics significantly affect the charging process.

It is shown that the polarization force, arising from interactions between thermal ions and highly charged dust grains, can accelerate charged dust grains and can also create spontaneous magnetic fields in a quasi-neutral dusty plasma. The present results are relevant for understanding the origin of dust grain acceleration and the generation of spontaneous magnetic fields in cosmic dusty plasmas.

The amplitude modulation of ion-acoustic waves is investigated in a plasma consisting of adiabatic warm ions, and two different populations of thermal electrons at different temperatures. The fluid equations are reduced to nonlinear Schrödinger equation by employing a multi-scale perturbation technique. A linear stability analysis for the wave packet amplitude reveals that long wavelengths are always stable, while modulational instability sets in for shorter wavelengths. It is shown that increasing the value of the hot-to-cold electron temperature ratio (μ), for a given value of the hot-to-cold electron density ratio (ν), favors instability. The role of the ion temperature is also discussed. In the limiting case ν = 0 (or ν → ∞), which correspond(s) to an ordinary (single) electron-ion plasma, the results of previous works are recovered.

Fully nonlinear electrostatic waves in a plasma containing electrons, positrons, and ions are investigated by solving the governing equations exactly. It is found that both smooth and spiky quasistationary waves exist, and large-amplitude waves necessarily have large-phase velocities, but small-amplitude waves can be both fast and slow.

We extend the quantum theory of Time Refraction for a generic spatial and temporal modulation of the optical properties of a medium, such as a dielectric or a gravitational field. The derivation of the local Bogoliubov transformations relating the global electromagnetic modes (valid over the entire span of space and time) with the local modes (valid for the vicinity of each spatial and temporal position) is presented and used in the evaluation of vacuum photon creation by the optical modulations of the medium. We use this approach to relate and review the results of different quantum effects such as the dynamical Casimir effect, space and Time Refraction, the Unruh effect and radiation from superluminal non-accelerated optical boundaries.

We show that the non-stationary ponderomotive force of a large-amplitude electromagnetic wave in a very dense quantum plasma with streaming degenerate electrons can spontaneously create d.c. magnetic fields. The present result can account for the seed magnetic fields in compact astrophysical objects and in the next-generation intense laser–solid density plasma interaction experiments.

The theory of particle diffusion in an electrostatic turbulent plasma is formulated by applying the direct-interaction approximation (DIA) to subensemble-averaged functions instead of conventional ensemble-averaged ones. This theory approximately incorporates the Lagrangian description into the DIA through decorrelation trajectories. The running diffusion coefficient is shown to be calculated by solving a nonlinear ordinary differential equation together with an equation for decorrelation trajectories and by averaging initial conditions at the starting point of trajectories.