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Title: On the generation of double layers from ion- and electron-acoustic instabilities

A plasma double layer (DL) is a nonlinear electrostatic structure that carries a uni-polar electric field parallel to the background magnetic field due to local charge separation. Past studies showed that DLs observed in space plasmas are mostly associated with the ion acoustic instability. Recent Van Allen Probes observations of parallel electric fields traveling much faster than the ion acoustic speed have motivated a computational study to test the hypothesis that a new type of DLs – electron acoustic DLs – generated from the electron acoustic instability are responsible for these electric fields. Nonlinear particle-in-cell simulations yield negative results, i.e. the hypothetical electron acoustic DLs cannot be formed in a way similar to ion acoustic DLs. We find that linear theory analysis and the simulations show that the frequencies of electron acoustic waves are too high for ions to respond and maintain charge separation required by DLs. However, our results do show that local density perturbations in a two-electron-component plasma can result in unipolar-like electric fields that propagate at the electron thermal speed, suggesting another potential explanation for the observations.
Authors:
 [1] ;  [1] ;  [2] ;  [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. Space Science Inst., Boulder, CO (United States)
Publication Date:
Report Number(s):
LA-UR-15-29656
Journal ID: ISSN 1070-664X
Grant/Contract Number:
AC52-06NA25396; IGPPS
Type:
Published Article
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 23; Journal Issue: 3; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE Laboratory Directed Research and Development (LDRD) Program; USDOE National Nuclear Security Administration (NNSA); National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Heliospheric and Magnetospheric Physics; double layer; ion acoustic; electron acoustic; PIC simulation
OSTI Identifier:
1248238
Alternate Identifier(s):
OSTI ID: 1242320; OSTI ID: 1338735