The laboratory experiment involved impinging a laser beam on an aluminum wire target creating a blow-off plasma which serves as a laboratory model for the solar plasma wind. The magnetopause is the boundary between the magnetosphere and the plasma wind where the magnetic pressure balances with the plasma wind pressure.
The plasma wind action on the magnetic field cause a current, , to form on the magnetopause. The calculation of this current can be found by forming an Ampere loop around the magnetopause and observing that the magnetic field upstream of the magnetopause is zero.
A plasma jet from a capacitor driven coaxial electrode device was used to create a plasma wind for a magnetosphere experiment. The plasma jet is formed by ablation of a molybdenum electrode from a capacitor bank discharge, combined with electrodynamic plasma acceleration forces. The discharge was triggered with a laser-produced plasma.
200 mJ laser pulse impinging on an Al target next to (a) a 4.5 mm radius Al block and (b) a 4.5 mm radius magnetic dipole. (c) and (d) have similar conditions as (a) and (b), respectively, with a 500 mJ laser pulse. The plasma wind flows from the right to the left of each frame (at the blue/green area) to the block in the frame middle. Plasma build up occurs on the face of the Al block in frames (a) and (c), whereas the plasma builds up on the polar cusp in the magnetic dipole case in frames (b) and (d). The magnetopause is marked on relevant images.
Data for the magnetosphere experiment using a plasma jet from a capacitor driven coaxial electrodes charged to 4900 V for creating the plasma wind. The plasma wind comes from the right originating from the bright source on the right which is the coaxial electrode set up. Rows (a) and (a) cont. have an Al block and rows (b) and (b) cont. have a magnetic dipole of same dimensions for times 4700–5700 ns. The magnetopause can be seen in (b) from 4900 to 5700 ns. Plasma bombardment on the objects begins about 400 ns sooner with the aluminum block, than the magnetic field case due to the opposition of the plasma from the magnetic field pressure. The plasma bombardment is concentrated on the face of the aluminum block as in (a) and on the cusp regions of the magnetic dipole as in (b).
ICCD image of laser-produced plasma progression where the input laser energy is and the target is thick Al wire. (a) is without fields and (b) is with enclosed fields. The laser comes in from the right and the majority of the plasma flows to the left. The plasma front can be seen expanding in (a) at times 35–80 ns. The colder plasma dissipates in (a) in times 140–400 ns. Plasma stagnation can be seen from the magnetic pressure in b) with significant build up on the poles of the magnet at times 80–440 ns.
The fringe shift is compared to the line integral of the electron density from a cylindrical calculation from HYADES. The initial laser energy was 3.7 J on a copper wire and the expansion time was 50 ns.
Simulation results for the five key plasma parameters for the plasma wind from a 200 mJ laser pulse impinging on an aluminum wire target at a distance 2.0 cm away from the ablated target. The simulation was in cylindrical geometry.
(a) Magnetosphere data from the laser-produced plasma experiments with HYADES calculations in both cylindrical and spherical cases, also with the cylindrical case adjusted for lateral expansion. (b) Magnetopause measurement from the coaxial plasma jet source with 4900 and 3000 V applied voltages.
The parameters of Earth’s magnetosphere are listed in the first column (Refs. 4 and 6). Scaling relations for Earth’s magnetosphere and the experimental setting as calculated by HYADES (see Sec. V) are listed in the second column. The scaling parameters are (length scale ratio parameter), (mass density scale ratio parameter), and (pressure scale ratio parameter).
Comparison between the measured laser-produced plasma front distance as produced by a 1064 nm laser beam impinging on a diameter aluminum wire as compared to HYADES calculations in planar, cylindrical, and spherical coordinates.
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