Abstract
Lasergenerated colliding plasma streams can serve as a testbed for the study of various astrophysical phenomena and the general physics of selforganization. For streams of a sufficiently high kinetic energy, collisions between the ions of one stream with the ions of the other stream are negligible, and the streams can penetrate through each other. On the other hand, the intrastream collisions for highMachnumber flows can still be very frequent, so that each stream can be described hydrodynamically. This paper presents an analytical study of the effects that these interpenetrating streams have on largescale magnetic fields either introduced by external coils or generated in the plasma near the laser targets. Specifically, a problem of the frozenin constraint is assessed and paradoxical features of the field advection in this system are revealed. A possibility of using this system for studies of magnetic reconnection is mentioned.
Work performed for U.S. DoE by LLNL under Contract No. DEAC5207NA27344.
I. INTRODUCTION
II. THE ELECTRON MOMENTUM EQUATION
III. STREAMLINES OF THE EFFECTIVE FLOW
IV. MAGNETIC FIELD ADVECTION
V. ADVECTION OF AN EXTERNALLY GENERATED POLOIDAL MAGNETIC FIELD
VI. DISCUSSION
Key Topics
 Magnetic fields
 55.0
 Plasma flows
 22.0
 Plasma collisions
 6.0
 Astrophysical plasmas
 5.0
 Lagrangian mechanics
 5.0
Figures
The geometry of the problem. Arrows show streamlines of the diverging ion flow in the vicinity of the targets. The size of the sources is assumed to be small compared to L, consistent with recent experiments.
The geometry of the problem. Arrows show streamlines of the diverging ion flow in the vicinity of the targets. The size of the sources is assumed to be small compared to L, consistent with recent experiments.
Streamlines of the effective flow: (a) half angular width of 30°, (b) half angular width of 60°, (c) half angular width of 90° (isotropic flow), and (d) half angular width of 60° and f = 0.5 (the upper jet is 2 times weaker than the lower one).
Streamlines of the effective flow: (a) half angular width of 30°, (b) half angular width of 60°, (c) half angular width of 90° (isotropic flow), and (d) half angular width of 60° and f = 0.5 (the upper jet is 2 times weaker than the lower one).
Comparison of magnetic field advection for a single and a double flow. The lower dotted line corresponds to a crosssection halfway between the midplane and the lower target. Streamlines of the single flow (dashed straight line) and effective flow (solid line) are virtually indistinguishable below this crosssection. The radial field distributions here are also essentially the same for single flow and the counterstreaming flows. This distribution is shown in Fig. 4 , curve 1. In the case of a single flow, the magnetic field decreases significantly from this crosssection to that near the midplane (the dotted line at a distance of 0.1L from the midplane), see curve 2 in Fig. 4 . Conversely, for the counterstreaming flows, the field at the distance of 0.1L from the midplane becomes higher than the field at the distance of 0.5L from the target.
Comparison of magnetic field advection for a single and a double flow. The lower dotted line corresponds to a crosssection halfway between the midplane and the lower target. Streamlines of the single flow (dashed straight line) and effective flow (solid line) are virtually indistinguishable below this crosssection. The radial field distributions here are also essentially the same for single flow and the counterstreaming flows. This distribution is shown in Fig. 4 , curve 1. In the case of a single flow, the magnetic field decreases significantly from this crosssection to that near the midplane (the dotted line at a distance of 0.1L from the midplane), see curve 2 in Fig. 4 . Conversely, for the counterstreaming flows, the field at the distance of 0.1L from the midplane becomes higher than the field at the distance of 0.5L from the target.
The magnetic field radial distribution: (1) halfway between the lower target and the midplane; (2) below the midplane for a single flow; below the midplane for symmetric counterstreaming flows; below the midplane for the symmetric counterstreaming flows. All the fields are normalized to the maximum value B _{0} of the magnetic field for the curve #1.
The magnetic field radial distribution: (1) halfway between the lower target and the midplane; (2) below the midplane for a single flow; below the midplane for symmetric counterstreaming flows; below the midplane for the symmetric counterstreaming flows. All the fields are normalized to the maximum value B _{0} of the magnetic field for the curve #1.
The magnetic field variation along the axis z for r = 0.5. The coordinates are normalized to the parameter L (Fig. 1 ). For the value of L as in Table I , the thickness of each of the “pancake” structures is ∼0.05 cm.
Radial magnetic field created by the effective flow from the bias field near the midplane: (a) The radial dependence of B_{pr} just below the midplane; the normalization field B* is defined as B* = 2B_{po} (r _{0} /L)^{2}. (b) The axial dependence of the radial field near the midplane for r/L = 0.5 and θ = 45°; dashed line indicates the smoothing of the transition due to the finite plasma resistivity.
Radial magnetic field created by the effective flow from the bias field near the midplane: (a) The radial dependence of B_{pr} just below the midplane; the normalization field B* is defined as B* = 2B_{po} (r _{0} /L)^{2}. (b) The axial dependence of the radial field near the midplane for r/L = 0.5 and θ = 45°; dashed line indicates the smoothing of the transition due to the finite plasma resistivity.
Streamlines for tilted targets: (a) Target orientation; (b) Streamlines for and half divergence angle of 60°. The axes of the flowsare shown by arrows. Flows have the same density. (c) Streamlines for and halfdivergence angle of 30°. The lower stream is two times less dense than the upper one.
Streamlines for tilted targets: (a) Target orientation; (b) Streamlines for and half divergence angle of 60°. The axes of the flowsare shown by arrows. Flows have the same density. (c) Streamlines for and halfdivergence angle of 30°. The lower stream is two times less dense than the upper one.
Tables
Parameters of each of the two streams in the midpoint between the targets for fully stripped carbon.
Parameters of each of the two streams in the midpoint between the targets for fully stripped carbon.
Derived parameters.
Derived parameters.
Characterization of the magnitude of the effects neglected in the electron momentum equation.
Characterization of the magnitude of the effects neglected in the electron momentum equation.
Article metrics loading...
Full text loading...
Most read this month
Most cited this month










Electron, photon, and ion beams from the relativistic interaction of Petawatt laser pulses with solid targets
Stephen P. Hatchett, Curtis G. Brown, Thomas E. Cowan, Eugene A. Henry, Joy S. Johnson, Michael H. Key, Jeffrey A. Koch, A. Bruce Langdon, Barbara F. Lasinski, Richard W. Lee, Andrew J. Mackinnon, Deanna M. Pennington, Michael D. Perry, Thomas W. Phillips, Markus Roth, T. Craig Sangster, Mike S. Singh, Richard A. Snavely, Mark A. Stoyer, Scott C. Wilks and Kazuhito Yasuike

Commenting has been disabled for this content