Generation of Collisionless Shocks by Laser-Plasma Piston in Magnetised Background: Experiment “BUW”

Theoretical basis and main results of the first successful large-scale, Laser-Plasma experiment “BUW”, on generation of Collisionless Shock Wave in magnetised Background Plasma, are presented. Our classic approach is based on the action of so called Magnetic Laminar Mechanism (or Larmor coupling) for collisionless interaction between interpenetrating super-Alfvenic plasma flows of Laser-Plasma and Background in transverse magnetic field

GENERATION OF QUASI-PERPENDIQULARE COLLISIONLESS SHOCKS BY LASER-PRODUCED PLASMA TO SIMULATE THE EFFECTS OF SUPER-COMPRESSION OF THE EARTH MAGNETOSPHERE

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On the possibility for laboratory simulation of generation of Alfvén disturbances in magnetic tubes in the solar atmosphere

The paper deals with generation of Alfvén plasma disturbances in magnetic flux tubes through exploding laser plasma in magnetized background plasma. Processes with similar effect of excitation of torsion-type waves seem to provide energy transfer from the solar photosphere to the corona. The studies were carried out at experimental stand KI-1 representing a high-vacuum chamber 1.2 m in diameter, 5 m in length, external magnetic field up to 500 G along the chamber axis, and up to 2·10–6 Torr pressure in operating mode. Laser plasma was produced when focusing the CO2 laser pulse on a flat polyethylene target, and then the laser plasma propagated in θ-pinch background hydrogen (or helium) plasma. As a result, the magnetic flux tube 15–20 cm in radius was experimentally simulated along the chamber axis and the external magnetic field direction. Also, the plasma density distribution in the tube was measured. Alfvén wave propagation along the magnetic field was registered from disturbance of the magnetic field transverse component Bφ and field-aligned current Jz. The disturbances propagate at a near-Alfvén velocity 70–90 km/s and they are of left-hand circular polarization of the transverse component of magnetic field. Presumably, the Alfvén wave is generated by the magnetic laminar mechanism of collisionless interaction between laser plasma cloud and background. A right-hand polarized high-frequency whistler predictor was registered which propagated before the Alfvén wave at a velocity of 300 km/s. The polarization direction changed with the Alfvén wave coming. Features of a slow magnetosonic wave as a sudden change in background plasma concentration along with simultaneous displacement of the external magnetic field were found. The disturbance propagates at ~20–30 km/s velocity, which is close to that of ion sound at low plasma beta value. From preliminary estimates, the disturbance transfers about 10 % of the original energy of laser plasma

GENERATION OF QUASI-PERPENDIQULARE COLLISIONLESS SHOCKS BY LASER-PRODUCED PLASMA TO SIMULATE THE EFFECTS OF SUPER-COMPRESSION OF THE EARTH MAGNETOSPHERE

-235-23

Laboratory and PIC simulations of collisionless interaction between expanding space plasma clouds and magnetic field with and without ionised background

Experiments on flute instability of plasma clouds at Alfven Mach-number Ma $\sim$ 0 and 1, and with varying ion's magnetization level have been realized at the KI-1 laser-plasma facility at the ILP of Novosibirsk, with similarity parameters close to those of Barium releases in Earth's magnetosphere. A number of diagnostics have allowed to characterize the dynamics of the cloud-magnetic field interaction, as well as flutes development, or suppression for Ma $>$ 1. Hybrid simulations with HAWAI2D code have reproduced the main observed features, such as the diamagnetic cavity dynamics, and flutes growth. A mode-mixing phenomenon related to Larmor rotation has been observed in simulations, which seems to lead to a reduction of mode number at later times in agreement with experimental results