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

Journal Article · Thu Mar 17 00:00:00 EDT 2016 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.4943881· OSTI ID:1248238

Fu, Xiangrong ^[1]; Cowee, Misa M. ^[1]; Gary, S. Peter ^[2]; Winske, Dan ^[1]

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1. Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
2. Space Science Institute, Boulder, Colorado 80301, USA

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.

• Research Organization: Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE Laboratory Directed Research and Development (LDRD) Program; USDOE National Nuclear Security Administration (NNSA); National Science Foundation (NSF)
• Grant/Contract Number: AC52-06NA25396; IGPPS
• OSTI ID: 1248238
• Alternate ID(s): OSTI ID: 1242320; OSTI ID: 1338735
• Report Number(s): LA-UR-15-29656; PHPAEN; 10.1063/1.4943881
• Journal Information: Physics of Plasmas, Vol. 23, Issue 3; ISSN 1070-664X
• Publisher: American Institute of Physics
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
Heliospheric and Magnetospheric Physics
double layer
ion acoustic
electron acoustic
PIC simulation