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.

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.

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

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.

Large amplitude ion-acoustic solitons are treated by a Sagdeev pseudopotential analysis, in a plasma with two adiabatic constituents, with the full inclusion of inertial and pressure effects for both. The sign of the supersonic species determines the polarity of the solitons, which are compressive in both constituents. Emphasis is placed on the determination of the soliton existence domains in compositional parameter space, allowing correct Sagdeev pseudopotential graphs to be easily generated, and offering insight into why limitations occur. Soliton velocities are bounded from below by the true acoustic velocity in the plasma model, and from above by the breakdown of the description when the supersonic ions reach their sonic point. Increases in the mass density ratio and the soliton velocity or decreases in the temperature ratio lead to increases in soliton amplitudes and decreases of the widths. Applications include hydrogen and electron–positron plasmas, and various kinds of dusty plasmas.

We review the concept of photon effective charge in a plasma, and extend it to the case of longitudinal photons or plasmons. A simple electrostatic fluid model is considered in a non-magnetized and non-relativistic plasma. The contribution of the ions to the plasmon charge is also considered.

The appearance of rogue waves is well known in oceanographics, optics, and cold matter systems. Here we show a possibility for the existence of atmospheric rogue waves.

Micrometeoroids entering the terrestrial atmosphere lead to two important related electrical effects. One is the electrification of the upper atmosphere along their paths and the other is the electrical charging of the micrometeoroids themselves. In this brief note we will emphasize the central role of the initial encounter speed of the incoming micrometeoroid, showing how it changes the altitude profiles of electron production and electrical charging, not just quantitatively but also qualitatively. We will discuss the underlying reasons for this, as well as their importance in meteor studies.

We develop a two dimensional, self-consistent, compressible fluid model to study evolution of Alfvenic modes in partially ionized astrophysical and space plasmas. The partially ionized plasma consists mainly of electrons, ions and significant neutral atoms. The nonlinear interactions amongst these species take place predominantly through direct collision or charge exchange processes. Our model uniquely describe the interaction processes between two distinctly evolving fluids. In our model, the electrons and ions are described by a single-fluid compressible magnetohydrodynamic (MHD) model and are coupled self-consistently to the neutral fluid via compressible hydrodynamic equations. Both plasma and neutral fluids are treated with different energy equations that adequately enable us to monitor non-adiabatic and thermal energy exchange processes between these two distinct fluids. Based on our self-consistent model, we find that the propagation speed of Alfvenic modes in space and astrophysical plasma is slowed down because these waves are damped predominantly due to direct collisions with the neutral atoms. Consequently, energy transfer takes place between plasma and neutral fluids. We describe the mode coupling processes that lead to the energy transfer between the plasma and neutral and corresponding spectral features.

Large-scale spatial variations of the guide magnetic field of interplanetary and interstellar plasmas give rise to the mirror force −(p⊥2/2mγB)∇B). The parallel component of this mirror force causes adiabatic focusing of the cosmic ray guiding center whereas the perpendicular component of the mirror force gives rise to the gradient and curvature drifts of the cosmic ray guiding center. Adiabatic focusing and the gradient and curvature drift terms additionally enter the Fokker–Planck transport equation for the gyrotropic cosmic ray particle phase space density in partially turbulent non-uniform magnetic fields. For magnetohydrodynamic turbulence with dominating magnetic fluctuations, the diffusion approximation is justified, which results in a modification of the diffusion–convection transport equation for the isotropic part of the gyrotropic phase space density from the additional focusing and drift terms. For axisymmetric undamped slab Alfvenic turbulence we show that all perpendicular spatial diffusion coefficients are caused by the non-vanishing gradient and curvature drift terms. For a specific (symmetric in μ) choice of the pitch-angle Fokker–Planck coefficients we show that the ratio of the perpendicular to parallel spatial diffusion coefficients apart from a constant is determined by the spatial first derivatives of the non-constant cosmic ray Larmor radius in the non-uniform magnetic field.

Nonlinear coupling of the motion in the three spatial degrees of freedom of a cold fluid electron–positron plasma is investigated. Exact solutions describing expanding flows with oscillations are obtained. It is found that the energy in the irrotational flow component is in general transferred to the rotational components, but not in the reversed direction. Furthermore, since the density evolution need not be related to all the three flow components, oscillations in one or two of the flow fields can be purely electromagnetic and are not accompanied by density oscillations.

The instabilities associated with drift waves can be suppressed (or even removed) by introducing negative ions into the usual electron ion plasma. The presence of negative ions causes a decrease in the amplitude of the perturbed electrostatic fields which are mainly produced by the difference of electron and ion masses. It is shown that the presence of negative ions is a stabilizing effect for drift eigenmode in a slab geometry and the frequency of this electrostatic mode is reduced. In a pure pair-ion plasma the convective cell mode can become unstable because of shear flow under certain conditions.

The nonlinear interaction between electromagnetic, electrostatic and gravitational waves in a Vlasov plasma is reconsidered. By using a orthonormal tetrad description the three-wave coupling coefficients are computed. Comparing with previous results, it is found that the present theory leads to algebraic expression that are much reduced, as compared to those computed using a coordinate frame formalism. Furthermore, here we calculate the back reaction on the gravitational waves, and a simple energy conservation law is deduced in the limit of a cold plasma.

We present here some very unusual experimental results on the dynamics of charged particle in a magnetic field which cannot be comprehended in terms of the Lorentz dynamics regarded, as per the current conceptual framework, as the appropriate one for the macro-scale description. Astonishingly, these results have been shown to be manifestations of a novel macro-scale quantum structure, designated as ‘transition amplitude wave’ (TAW), riding with the guiding centre trajectory, which is generated in the latter trajectory in consequence of the scattering of the particle with a fixed scattering centre. One set of observed results is thus identified as matter wave interference effects on the macro-scale attributable to this entity. The other enigmatic observation demonstrates the detection of a curl-free magnetic vector potential on the macro-scale, which is also shown to be a consequence of the TAW embedded in the Lorentz trajectory. These enigmatic results thus point to the unravelling of a new concept of a ‘dressed’ Lorentz trajectory—dressed with the TAW—accountable for these results, as against the ‘bare’ trajectory. These results and the formalism which enables one to comprehend them have led to the emergence of a new class of phenomena which display quantum properties on the macro-scale.

A full-scale numerical study is performed of the nonlinear interaction between a large-amplitude electromagnetic wave and the Earth's ionosphere, and of the stimulated electromagnetic emission emerging from the turbulent layer, during the first 10 milliseconds after switch-on of the radio transmitter. The frequency spectra are downshifted in frequency and appear to emerge from a region somewhat below the cutoff of the O mode, which is characterized by Langmuir wave turbulence and localized Langmuir envelopes trapped in ion density cavities. The spectral features of escaping O-mode waves are very similar to those observed in experiments. The frequency components of Z-mode waves, trapped in the region between the O- and Z-mode cutoffs show strongly asymmetric and downshifted spectra.

Dust in fusion plasma is a quickly developing field. In this paper the current states of theory and modeling of dust in fusion plasma are discussed and their results compared with available experimental data.

The dispersion relation arising from a Vlasov–Poisson system with a Bohmian force term is examined and compared to the more fundamental Bohm and Pines dispersion relation for quantum plasmas. Discrepancies are found already when considering the leading order thermal effects. The time-averaged energy densities for longitudinal modes are also shown to be noticeably different.

Amplification of a short laser pulse by means of its interaction with a counter-propagating long pulse in a plasma has been suggested as a way of reaching high intensities. Two regimes have been discussed in the literature. The first is the Raman regime, where the process is backward Raman scattering, described by the standard equations for resonant three-wave coupling, while the second is the Compton regime, in which electron dynamics is dominated by the ponderomotive force generated by the high-frequency wave, and electrons behave as single particles rather than producing a Langmuir wave. Our aim here is to use a simple model of electron dynamics to investigate the transition between these regimes.

A dispersion equation, which describes the interaction of low-density electron beam with a degenerate electron quantum plasma, is derived and examined for some interesting cases. In addition to the instabilities similar to those for classical plasma, due to the quantum effect, a new type of instability is found. Growth rates of these new modes, which are purely quantum, are obtained. Furthermore, the excitation of Bogolyubov's type of spectrum by a strong electric field is discussed.

The dust ion-acoustic solitary waves (SWs) in an unmagnetized dusty adiabatic electronegative plasma containing inertialess adiabatic electrons, inertial single charged adiabatic positive and negative ions, and stationary arbitrarily (positively and negatively) charged dust have been theoretically studied. The reductive perturbation method has been employed to derive the Korteweg-de Vries equation which admits an SW solution. The combined effects of the adiabaticity of plasma particles, inertia of positive or negative ions, and presence of positively or negatively charged dust, which are found to significantly modify the basic features of small but finite-amplitude dust-ion-acoustic SWs, are explicitly examined. The implications of our results in space and laboratory dusty electronegative plasmas are briefly discussed.