The prospects of using extreme relativistic laser-matter interactions for laboratory astrophysics are discussed. Laser-driven process simulation of matter dynamics at ultra-high energy density is proposed for the studies of astrophysical compact objects and the early universe.

Magnetic field generation in the Universe is still an open problem. Possible mechanisms involve the Weibel instability, due to anisotropic phase-space distributions, as well as the Biermann battery, due to misaligned density and temperature gradients. These mechanisms can be reproduced in scaled laboratory experiments. In this contribution we estimate the relative importance of these two processes and explore the laser-energy requirements for producing Weibel dominated shocks.

Cosmic rays are accelerated in astrophysical plasmas which collide at supersonic speeds where shock waves are formed, and along with other instabilities, they compete for the dissipation and acceleration mechanisms. The diffusive acceleration mechanism plays a leading role in the explanation of very high energy cosmic rays observed. In this mechanism, particles are repeatedly gaining energy in multiple crossings of an astrophysical shock discontinuity, due to collisions with upstream and downstream magnetic scattering centers, resulting in a power-law spectrum extending up to very high energies. Relativistic jets and their shocks in Active Galactic Nuclei (AGN) is a prominent source for particle acceleration. Especially, relativistic single or multiple shocks have been theorized and observed along the jets of AGN and are claimed to be responsible for accelerating even the highest-energy cosmic rays observed. In this paper we will report and discuss the cosmic ray acceleration efficiency and properties of single or multiple shocks in the limit of relativistic plasmas in AGN jet environments.

A two-dimensional numerical study of the expansion of a dense plasma through a more rarefied one is reported. The electrostatic ion-acoustic shock, which is generated during the expansion, accelerates the electrons of the rarefied plasma inducing a superthermal population which reduces electron thermal anisotropy. The Weibel instability is therefore not triggered and no self-generated magnetic fields are observed, in contrast with published theoretical results dealing with plasma expansion into vacuum.

Using powerful lasers, we are now able to produce in laboratory relevant regimes of density, temperature and velocity to create a diagnosable exact scaled model of magnetic cataclysmic variables accretion column. We present here preliminary results of a numerical modeling of these astrophysical objects which will allow us to precise the experimental setup of future experiments.

CNES, ESA and NASA have invested in helioseismic and asteroseismic disciplines for 2 decades with SoHO (1995–2015), COROT (2006–2013), KEPLER (2009–2014), PICARD (2010–2013) and SDO (2010–2015). These missions focus on the stellar internal dynamics and their influence of neighboring planets. Progress along this path requires that the microscopic physics is well under control, but several seismic probes indicate some discrepancies which justify new investigations of the energy transport in radiative zones of the Sun and massive stars, despite strong efforts dedicated to reaction rates, screening, equation of state and opacity coefficients between 1990 and 2000. We describe here how the OPAC consortium tackles the complex problem of photon absorption by matter both theoretically and experimentally, by using high energy laser facilities. These studies might be also useful for other disciplines like fusion for energy and X-ray spectroscopy astronomy.

We discuss the role of Configuration Interaction (CI) and the influence of the number of configurations taken into account in the calculations of nickel and iron spectral opacities provided by the OPAC international collaboration, including statistical approaches (SCO, CASSANDRA, STA), detailed accounting (OPAS, LEDCOP, OP, HULLAC-v9) or hybrid method (SCO-RCG). Opacity calculations are presented for a temperature T of 27.3 eV and a density of 3.4 mg/cm3, conditions relevant for pulsating stellar envelopes.

Laboratory experiments demonstrate that current sheets evolving in magnetized plasmas can give rise to both flare-type events and generation of energetic plasma jets.

We report laboratory measurements of the Zeeman response of lines in the 0-0 Wing-Ford band of the F-X system (λ ~ 1 μm) of FeH, measured in magnetic fields 0.3 – 0.5 Tesla. New Landé factors are used to deduce the magnetic field in sunspots from Stokes V profiles recorded at the solar telescope THEMIS. The magnetic field deduced from atomic lines (Ti, Fe) is slightly higher than that found from FeH.

The influence of a magnetic field on the broadening of spectral lines and transition arrays in complex spectra is investigated. The anomalous absorption or emission Zeeman pattern is a superposition of many profiles with different relative strengths, shifts, widths, asymmetries and sharpnesses. The σ and π profiles can be described statistically, using the moments of the Zeeman components. We present two statistical modellings: the first one provides a diagnostic of the magnetic field and the second one can be used to include the effect of a magnetic field on simulated atomic spectra in an approximate way.

The optical spectra of L- and T-type dwarfs exhibit a continuum dominated by the far wings of the absorption profiles of the Na 3s-3p and K 4s-4p doublets perturbed by molecular hydrogen and helium. We examine the K resonance line wing and core with a unified line profile theory and compare to laboratory experiments and observations of the cool brown dwarf ϵ Indi Ba,b.

Stark broadening theories and calculations have been extensively developed for about 50 years. The theory can now be considered as mature for many applications, especially for accurate spectroscopic diagnostics and modelling. This requires the knowledge of numerous collisional line profiles, especially for very low abundant atoms and ions which are used as probes for modern spectroscopic diagnostics in astrophysics. Nowadays, the access to such data via an on line database becomes essential. STARK-B (http://stark-b.obspm.fr) is a collaborative project between the Astronomical Observatory of Belgrade and the Laboratoire d’Étude du Rayonnement et de la matière en Astrophysique (LERMA). It is a database of calculated widths and shifts of isolated lines of atoms and ions due to electron and ion collisions (impacts). It is devoted to modelling and spectroscopic diagnostics of stellar atmospheres and envelopes, laboratory plasmas, laser equipments and technological plasmas. Hence, the domain of temperatures and densities covered by the tables is wide and depends on the ionization degree of the considered ion. The STARK-B database is a part of VAMDC (Virtual Atomic and Molecular Data Centre, http://www.vamdc.eu), which is an European Union funded collaboration between groups involved in the generation and use of atomic and molecular data. VAMDC aims to build a secure, documented, flexible and interoperable e-science environment-based interface to existing atomic and molecular data.

Energy in the solar system is constantly being converted from one form to another. Often these processes take the form of dramatic events such as solar eruptions or geomagnetic storms with important societal impacts. Understanding energy conversion and magnetic storms is one of the grand challenges facing science and poses a great cultural and scientific puzzle. We plan to use a new modelling approach based on combining state of the art supercomputers with state of the art numerical methods that allow us to capture the key aspect in energy conversion: the interplay of small and large scales. At the core of energy conversion is the ability of macroscopic systems to store and process vast amounts of energy while at the same time requiring microscopic processes at the moment the energy is released. To describe and predict how energy can be stored for long periods and why it is then suddenly released, a complete description down to the level of tracking the trajectory of single particles is needed.

We review the main results of our previous works, in which we have investigated the development of the Kelvin-Helmholtz (KH) instability in the transitional regime from sub-magnetosonic to super-magnetosonic by varying the solar wind velocity, in conditions typical of those observed at the Earth’s magnetopause flanks. In super-magnetosonic regimes, we show that the vortices produced by the development of the KH instability act as an obstacle in the plasma flow and may generate quasi-perpendicular magnetosonic shock structures extending well outside the region of velocity shear.

Results are presented from studies of the process of plasma acceleration along the current sheet width under different experimental conditions. The behavior of the neutral component is included in the analysis.

The aim of this work is the analysis of the different transport regimes related to the propagation in the solar wind of solar energetic particles (SEPs) generated by impulsive events like solar flares. A numerical implementation of a Lévy random walk for parallel particle transport is developed, which allows obtaining superdiffusive transport. The comparison between the flows measured by satellites and fluxes extracted from the numerical simulation, will contribute to a deeper understanding of the mechanisms underlying the presence of superdiffusive regimes of SEP transport in interplanetary medium.

It can be argued that all astrophysical jets, from lowly sub-stellar objects such as young brown dwarfs to massive black holes at the centre of AGN, are generated by the same basic physical mechanism. While the nature of that mechanism is still debated, jets from young stars may represent our best chance of deciphering it. There are several reasons for this statement. First of all they are nearby, thus affording us not only high spatial resolution studies of the “central engine” but also time-resolved analysis of their kinematics. Moreover as they radiate emission lines, spectroscopy can reveal radial velocities, temperature, density, ion fraction, etc., along their flow. This wealth of data is a challenge to the theorist/computational simulator but also a highly effective means of discriminating between models. In addition, the observations tightly constrain laboratory experiments. Here, I briefly review what is known about conditions in jets from young stars as a guide to experiments, their generation including their link with accretion disks, and their evolution from the earliest proto-stellar to pre-main sequence phase.

We investigate the launching process of jets from accretion disks by means of axisymmetric MHD simulations. Here, we present results of numerical MHD simulations investigating how magnetic diffusivity and numerical resolution may affect the ejection-to-accretion fraction and the asymptotic outflow structure.

Outflows and jets are intimately related to the formation of stars, and play a central role in redistributing mass, energy and angular momentum within the core, disk and parent cloud. The interplay between magnetic field and rotation is widely thought to be responsible for launching and collimating these outflows. Shear induced by differential rotation along initially poloidal field lines results in an azimuthal component of the magnetic field being generated; the magnetic pressure gradient then accelerates the plasma, and inflates bipolar magnetic cavities within the circumstellar matter. However, the resulting winding of the magnetic field can be potentially disrupted by magneto-hydrodynamic instabilities. To better understand the role of magnetic fields in shaping these ouflows, a series of experiments on pulsed-power z-pinch machines have been developed. In this talk I will present results related to the formation of jets in young stellar objects and in the laboratory, and draw a parallel between the two systems.