Laboratory Simulation of Magnetized Plasma Turbulence in the Intergalactic Medium

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We propose an experimental programme to probe one of the greatest puzzles of modern astrophysics: the generation and amplification of magnetic fields ubiquitously found in the Universe. The aim is to demonstrate amplification of magnetic fields by turbulent dynamo - a great challenge of modern experimental plasma physics. We will also study the distribution of turbulent energy between velocity, magnetic and density fluctuations, providing a comprehensive experimental characterisation of the energy cascade in a turbulent plasma. Magnetic fields are ubiquitously observed in the Universe. Their energy density is comparable to the energy density of the mean plasma flows, so the magnetic fields are essential players in the dynamics of the luminous matter. The total magnetic energy represents a sizable fraction of the cosmic energy budget. What is the origin of these fields? The fact that they are ubiquitous, stochastic and dynamically strong suggests that a universal physical mechanism is at play. The most popular scenario of the cosmic magnetogenesis is that the field grows via some form of turbulent dynamo - fast (exponential) amplification of stochastic field by turbulent motions into which it is embedded, starting from an initial small seed. Understanding magnetogenesis is part of the broader challenge of understanding cosmic turbulence, and the way different form of energies (thermal, turbulent, magnetic) are partitioned on various scales.With the advent of high-power lasers, a new field of research has opened where, using simple scaling relations, astrophysical environments can be reproduced in the laboratory. The similarity is sufficiently close to make such experiments of high interest. Here we propose to establish an experimental platform using laser-produced plasmas where magnetic fields are produced and amplified by turbulence. In the turbulent plasma, small magnetic fields are initially generated by electrical currents resulting from mis-aligned density and temperature gradients - the so-called Biermann battery effect. By then characterizing the properties of such plasmas and the embedded magnetic fields, we intend to show that those tiny fields can be amplified to much larger values, and up to equipartition with the kinetic energy of the turbulent motions. We will use these experiments to measure the magnetic-energy, density and velocity spectra in the turbulent plasma, thus addressing the details of the energy cascade. Thus, our work would establish, for the first time experimentally, the soundness of the theoretical expectation that tiny seeds produced at protogalactic structures (~10^-21 G) can be amplified to observed dynamically significant values (~10^-6 G) in cosmologically short times.