Particle-in-cell (PIC) methods have a long history in the study of laser-plasma interactions. Early electromagnetic codes used Yee staggered grid for field variables combined with leapfrog EM-field update and Boris algorithm particle pushing. The general properties such schemes are well documented. Modern PIC tend to add these high-order shape functions particles, Poisson preserving updates, collisions, ionisation, hybrid scheme solid density high-field QED effects. In addition physics...

In simulations of a 10 PW laser striking solid, we demonstrate the possibility producing pure electron-positron plasma by same processes as those thought to operate in high-energy astrophysical environments. A maximum positron density 10(26) m(-3) can be achieved, 7 orders magnitude greater than achieved previous experiments. Additionally, 35% energy is converted burst γ rays intensity 10(22) W cm(-2), potentially most intense γ-ray source available laboratory. This absorption results strong...

In simulations of a 12.5 PW laser (focussed intensity I=4×1023Wcm−2) striking solid aluminum target, 10% the energy is converted to gamma-rays. A dense electron-positron plasma generated with maximum density 1026m−3, seven orders magnitude denser than pure e− e+ plasmas 1PW lasers. When power increased 320 (I=1025Wcm−2), 40% gamma-ray photons and pairs. both cases, there strong feedback between QED emission processes physics, defining feature new “QED-plasma” regime reached in these interactions.

A sequence of TRACE 171 Å observations taken on 2001 May 13 shows evidence flare-induced, transverse coronal loop oscillations. We revisit this particular data set and present the presence spatially resolved higher harmonics in displacements. The oscillations are identified as second-harmonic, fast MHD kink waves (periods 577-672 s), with (250-346 s) also present. apparent absence fundamental mode fact that it is second harmonic (P2) dominates oscillatory behavior may shed more light either...

A novel absorption mechanism for linearly polarized lasers propagating in relativistically underdense solids the ultrarelativistic (a ~ 100) regime is presented. The based on strong synchrotron emission from electrons reinjected into laser by space charge field they generate at front of pulse. This absorption, termed electron emission, due to a coupling conventional plasma physics processes quantum electrodynamic low density intensities above 10(22) W/cm(2). Reinjected identified 2D...

ABSTRACT Physical processes that may lead to solar chromospheric heating are analyzed using high-resolution 1.5D non-ideal MHD modeling. We demonstrate it is possible heat the plasma by direct resistive dissipation of high-frequency Alfvén waves through Pedersen resistivity. However, this unlikely be sufficient balance radiative and conductive losses unless unrealistic field strengths or photospheric velocities used. The precise profile determined input driving spectrum, since in there no...

Context. This paper extends the models of Craig & McClymont (1991, ApJ, 371, L41) and McLaughlin Hood (2004, A&A, 420, 1129) to include finite β nonlinear effects.

The peculiarities of the propagating transverse waves observed in solar corona with Coronal Multi-channel Polarimeter (CoMP) indicate existence fine field structuring coronal density. We present results numerical simulations studying evolution a localised magneto-hydrodynamic wave uniform magnetic field. consider two initial low plasma-beta equilibria: one homogeneous density, and field-aligned dense structure (such as loop or plume). perpendicular localisation strongly determines angular...

1D and 2D PIC simulations of light ion acceleration by irradiation structured thin foils short pulse, high intensity lasers have been performed. When the back coating material is thicker than typical scale length for TNSA fields energy spectra contain peaks. These peaks are found to be due ions an electric field which builds up at internal interfaces between materials with different electron number densities. The generated incomplete neutralization charge built head hot beam as it crosses...

The decay rate of vertical kink waves in a curved flux tube is modeled numerically. full MHD equations are solved for equilibrium an arcade geometry and the ψ, integral over modulus velocity perpendicular to local magnetic field, measured. These simulations 2D thus restricted oscillations loop plane. found increase with increasing wavelength, β decreasing density contrast ratio. wave tunneling effect shown be possible mechanism high recent observed oscillation reported by Wang & Solanki (2004).

<i>Aims. <i/>We perform an advanced study of the fast magnetoacoustic sausage oscillations coronal loops in context MHD seismology to establish dependence mode period and cut-off wavenumber on plasma-<i>β<i/> loop-filling plasma. A parametric ratios for different harmonics is also carried out.<i>Methods. <i/>Full magnetohydrodynamic numerical simulations were performed using Lare2d, simulating hot, dense a magnetic slab environment. The symmetric Epstein profile simple step-function both...

At laser intensities above 1023 W/cm2, the interaction of a with plasma is qualitatively different to interactions at lower intensities. In this intensity regime, solid targets start become relativistically underdense, gamma-ray production by synchrotron emission starts an important feature dynamics and, even higher intensities, electron-positron pair non-linear Breit-Wheeler process occur. paper, analysis presented effects target density, intensity, preplasma properties, and other...

Aims.We present results from numerical simulations that study the interaction of a pair twisted, buoyant magnetic flux tubes, which rise solar interior into outer atmosphere Sun. The aim our new model is to reproduce some dynamic phenomena in self-consistent manner.

Previous work on the interaction of high power lasers with density targets have identified that emission is primarily from within skin layer at target front (e.g. Ridgers et al 2012 Phys. Rev. Lett. 108 165006). This mechanism inefficient when compared to Reinjected Electron Synchrotron Emission (RESE) for laser low solids (Brady 109 245006). However, these detailed analyses mechanisms were mainly based 1D simulations and so did not incorporate some important 2D effects. In this paper are...

The damping of slow magnetoacoustic coronal loop oscillations by shock dissipation is investigated. Observations large-amplitude slow-mode observations made SUMER show a clear dependency the rate on oscillation amplitude. Fully nonlinear MHD simulations in presence thermal conduction are performed that an important mechanism at large amplitudes, enhancing up to 50% above given alone. A comparison between numerical and shows although model can indeed produce enhanced function amplitude, we...

Solar coronal equilibrium fields are often constructed by nonlinear force-free field (NLFFF) extrapolation from photospheric magnetograms. It is well known that the not and correct lower boundary for NLFFF construction ought to be top of chromosphere. To compensate this, pre-filtering algorithms applied data remove non-force-free components. Such models, while physically constrained, do address mechanisms may responsible becoming force-free. The chromospheric can change through, example,...

To better understand the decay of vertically polarised fast kink modes coronal loops by mechanism wave tunneling, simulations are performed in straight flux slabs which have Alfvén speed profiles include a tunneling region. The rates found to be determined mode number trapped and thickness Two analytical models suggested explain observed decay. first is extension work Roberts (1981, Sol. Phys., 69, 39) finite region, second simpler model yields an solution for relationship between rate,...

Quasilinear theory has long been used to treat the problem of a weak electron beam interacting with plasma and generating Langmuir waves. Its extension weak-turbulence treats resonant interactions these waves other wave modes, in particular, ion-sound These are strongly damped equal ion temperatures, as sometimes seen in, for example, solar corona wind. Weak turbulence is derived damping limit, term describing then added. In this paper, we use EPOCH particle-in-cell code numerically test...

Two of the central problems in our understanding solar chromosphere are how upper is heated and what drives spicules. Estimates required chromospheric heating, based on radiative conductive losses, suggest a rate ∼0.1 erg cm−3 s−1 lower drops to ∼10−3 chromosphere. The also permeated by spicules, higher density plasma from atmosphere propelled upwards at speeds ∼10–20 km s−1, for so-called Type I which reach heights ∼3000–5000 above photosphere. A clearer dynamics, its formation spicules...

Strongly localized concentrations or depressions of plasma density and magnetic field strength ('blobs') are ubiquitous in the edge region tokamak fusion experiments. The existing literature this area focuses primarily on blobs sufficiently large that a fluid description is appropriate. However, blob population may include some—not necessarily easily detectable—whose characteristic lengthscales order ion gyro-scales. This implies at level unlikely to capture full dynamics. Here, therefore,...

We present particle-in-cell (PIC) simulations of minority energetic protons in deuterium plasmas, which demonstrate a collective instability responsible for emission near the lower hybrid frequency and its harmonics. The capture drift regime relevant to tokamak fusion show further that excited electromagnetic fields collectively collisionlessly couple free energy from directed electron motion. This results an asymmetric tail antiparallel magnetic field. focus on obliquely propagating modes...

A novel mechanism for initiating laser filamentation intensities above 5 × 1017 W/cm2 is presented, seeded by the transient interference of an incident and its Raman backscattered daughter wave. For lasers propagating up short scale-length density gradients, reflectivity peaked near relativistically corrected quarter critical surface (RCQCS) thus observed to start on this surface. The at RCQCS occurs timescales comparable period. series 2D particle-in-cell (PIC) simulations confirm physical...

We present a model-independent experimental method for calibrating the amplitude of low-frequency electric field in an alkali vapor cell. Three-photon excitation to Rydberg state atomic rubidium produces electromagnetically induced transparency (EIT) signal that is sensitive fields originating outside superpose measured shape EIT resonance presence with expected line shape, obtained by numerically time-averaging effect DC-Stark shift. The value fractional transmission, caused Faraday...

Electron-positron plasmas are a prominent feature of the high energy Universe. In relativistic winds from pulsars and black holes it is thought that non-linear quantum electrodynamics (QED) processes cause electromagnetic to cascade into an e-e+ plasma. We show next-generation 10PW lasers, available in next few years, will generate such density pairs they create micro-laboratory for first experimental study similarly generated simulations laser striking solid we demonstrate production pure...