Abstract
The whistleranisotropyinstability is studied in a magnetized, homogeneous, collisionless plasma model. The electrons (denoted by subscript e) are represented initially with a single biMaxwellian velocity distribution with a temperature anisotropy, where and denote directions perpendicular and parallel to the background magnetic field, respectively. Kinetic linear dispersion theory predicts that, if the ratio of the electron plasma frequency to the electron cyclotron frequency is greater than unity and , the maximum growth rate of this instability is at parallel propagation, where the fluctuating fields are strictly electromagnetic. At smaller values of , however, the maximum growth rate shifts to propagation oblique to and the fluctuating electric fields become predominantly electrostatic. Linear theory and twodimensional particleincell simulations are used to examine the consequences of this transition. Three simulations are carried out, with initial , 0.03, and 0.01. The fluctuating fields of the run are predominantly electromagnetic, with nonlinear consequences similar to those of simulations already described in the literature. In contrast, the growth of fluctuations at oblique propagation in the low electron runs leads to a significant , which heats the electrons leading to the formation of a substantial suprathermal component in the electron parallel velocity distribution.
This work was performed under the auspices of the U.S. Department of Energy (DOE). It was supported in part by the Defense Threat Reduction Agency under the “Basic Research for Combating Weapons of Mass Destruction (WMD)” Program, projects IACRO 104946I and IACRO 104284I, and in part by the Dynamic Radiation Environment Assimilation Model (DREAM) Project at Los Alamos National Laboratory. We are grateful to the sponsors of DREAM for financial and technical support.
I. INTRODUCTION
II. LINEAR THEORY
III. PARTICLEINCELL SIMULATIONS
IV. CONCLUSIONS
Key Topics
 Magnetic anisotropy
 12.0
 Particleincell method
 10.0
 Maxwell equations
 9.0
 Electric fields
 8.0
 Electrostatics
 8.0
Figures
The linear growth rate of the whistler anisotropy instability as a function of the angle of propagation for three different values of as labeled. Here and in Figures 2–4, , , , and . Further, and the electron anisotropies are chosen to yield . (a) and . (b) and .
The linear growth rate of the whistler anisotropy instability as a function of the angle of propagation for three different values of as labeled. Here and in Figures 2–4, , , , and . Further, and the electron anisotropies are chosen to yield . (a) and . (b) and .
Linear theory results: The fluctuating field ratios for the whistler anisotropy instability as functions of the angle of propagation for the wavenumbers of maximum growth rate using the same parameters as stated in the caption of Figure 1. (a) Fluctuating magnetic field ratios and (b) fluctuating electric field ratios.
Linear theory results: The fluctuating field ratios for the whistler anisotropy instability as functions of the angle of propagation for the wavenumbers of maximum growth rate using the same parameters as stated in the caption of Figure 1. (a) Fluctuating magnetic field ratios and (b) fluctuating electric field ratios.
Linear properties of the whistler anisotropy instability at as functions of . (a) The real frequency, (b) the angle of propagation, (c) the magnitude of the wavenumber, (d) the electron temperature anisotropy, and (e) the electric/magnetic field energy ratio [Eq. (1)]. For all cases at which the maximum growth rate is at oblique propagation, that is, , .
Linear properties of the whistler anisotropy instability at as functions of . (a) The real frequency, (b) the angle of propagation, (c) the magnitude of the wavenumber, (d) the electron temperature anisotropy, and (e) the electric/magnetic field energy ratio [Eq. (1)]. For all cases at which the maximum growth rate is at oblique propagation, that is, , .
(Color online) The linear growth rate of the whistler anisotropy instability as a function of wavenumber k and angle of propagation for the initial plasma parameters of the three simulations defined in the text: (a) Run 1 with , (b) Run 2 with , and (c) Run 3 with . The heavy black lines in each panel correspond to the condition . The asterisk in each panel represents the maximum growth rate of . Note that the minimum value of the color scale corresponds to so that larger damping rates saturate in the plot.
(Color online) The linear growth rate of the whistler anisotropy instability as a function of wavenumber k and angle of propagation for the initial plasma parameters of the three simulations defined in the text: (a) Run 1 with , (b) Run 2 with , and (c) Run 3 with . The heavy black lines in each panel correspond to the condition . The asterisk in each panel represents the maximum growth rate of . Note that the minimum value of the color scale corresponds to so that larger damping rates saturate in the plot.
(Color online) PIC simulation results at for (left column) and (right column) . The heavy black lines of the righthand panels correspond to the black lines of Figure 4, that is, the condition .
(Color online) PIC simulation results at for (left column) and (right column) . The heavy black lines of the righthand panels correspond to the black lines of Figure 4, that is, the condition .
(Color online) PIC simulation results: The electron temperature anisotropy, the fluctuating magnetic field component energies, and the fluctuating electric field component energies as functions of time for [(a), (d), (g)] Run 1 with , [(b), (e), (h)] Run 2 with , and [(c), (f), (i)] Run 3 with . In panels (d), (e), and (f), the red lines denote , the green lines denote , the blue lines denote , and the black lines denote . In panels (g), (h), and (i), the red lines denote , the green lines denote , the blue lines denote , and the black lines denote .
(Color online) PIC simulation results: The electron temperature anisotropy, the fluctuating magnetic field component energies, and the fluctuating electric field component energies as functions of time for [(a), (d), (g)] Run 1 with , [(b), (e), (h)] Run 2 with , and [(c), (f), (i)] Run 3 with . In panels (d), (e), and (f), the red lines denote , the green lines denote , the blue lines denote , and the black lines denote . In panels (g), (h), and (i), the red lines denote , the green lines denote , the blue lines denote , and the black lines denote .
PIC simulation results for the reduced electron velocity distribution . (a) Run 1 with , (b) Run 2 with , and (c) Run 3 with . The dashed curves represent the initial Maxwellian distributions, and the solid curves display the parallel velocity distributions at .
PIC simulation results for the reduced electron velocity distribution . (a) Run 1 with , (b) Run 2 with , and (c) Run 3 with . The dashed curves represent the initial Maxwellian distributions, and the solid curves display the parallel velocity distributions at .
PIC simulation results from Run 3 for part of the reduced electron velocity distribution at four simulation times. The dashed line represents the initial Maxwellian distribution, the dotted line corresponds to , the longdashedshortdashed line corresponds to , and the solid line corresponds to .
PIC simulation results from Run 3 for part of the reduced electron velocity distribution at four simulation times. The dashed line represents the initial Maxwellian distribution, the dotted line corresponds to , the longdashedshortdashed line corresponds to , and the solid line corresponds to .
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