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Title: The electron forewake: Shadowing and drift-energization as flowing magnetized plasma encounters an obstacle

Flow of magnetized plasma past an obstacle creates a traditional wake, but also a forewake region arising from shadowing of electrons. The electron forewakes resulting from supersonic flows past insulating and floating-potential obstacles are explored with 2D electrostatic particle-in-cell simula-tions, using a physical ion to electron mass ratio. Drift-energization is discovered to give rise to modifications to the electron velocity-distribution, including a slope-reversal, providing a novel drive of forewake instability. The slope-reversal is present at certain locations in all the simula-tions, and appears to be quite robustly generated. Wings of enhanced electron density are observed in some of the simulations, also associated with drift-energization. In the simulations with a floating-potential obstacle, the specific potential structure behind that obstacle allows fast electrons to cross the wake, giving rise to a more traditional shadowing-driven two-stream instability. In conclusion, fluctuations associated with such instability are observed in the simulations, but this instability-mechanism is expected to be more sensitive to the plasma parameters than that associated with the slope-reversal.
Authors:
ORCiD logo [1] ;  [1]
  1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
Publication Date:
Grant/Contract Number:
SC0010491
Type:
Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 22; Journal Issue: 10; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Research Org:
Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
OSTI Identifier:
1469378
Alternate Identifier(s):
OSTI ID: 1223158

Haakonsen, Christian Bernt, and Hutchinson, Ian H. The electron forewake: Shadowing and drift-energization as flowing magnetized plasma encounters an obstacle. United States: N. p., Web. doi:10.1063/1.4932006.
Haakonsen, Christian Bernt, & Hutchinson, Ian H. The electron forewake: Shadowing and drift-energization as flowing magnetized plasma encounters an obstacle. United States. doi:10.1063/1.4932006.
Haakonsen, Christian Bernt, and Hutchinson, Ian H. 2015. "The electron forewake: Shadowing and drift-energization as flowing magnetized plasma encounters an obstacle". United States. doi:10.1063/1.4932006. https://www.osti.gov/servlets/purl/1469378.
@article{osti_1469378,
title = {The electron forewake: Shadowing and drift-energization as flowing magnetized plasma encounters an obstacle},
author = {Haakonsen, Christian Bernt and Hutchinson, Ian H.},
abstractNote = {Flow of magnetized plasma past an obstacle creates a traditional wake, but also a forewake region arising from shadowing of electrons. The electron forewakes resulting from supersonic flows past insulating and floating-potential obstacles are explored with 2D electrostatic particle-in-cell simula-tions, using a physical ion to electron mass ratio. Drift-energization is discovered to give rise to modifications to the electron velocity-distribution, including a slope-reversal, providing a novel drive of forewake instability. The slope-reversal is present at certain locations in all the simula-tions, and appears to be quite robustly generated. Wings of enhanced electron density are observed in some of the simulations, also associated with drift-energization. In the simulations with a floating-potential obstacle, the specific potential structure behind that obstacle allows fast electrons to cross the wake, giving rise to a more traditional shadowing-driven two-stream instability. In conclusion, fluctuations associated with such instability are observed in the simulations, but this instability-mechanism is expected to be more sensitive to the plasma parameters than that associated with the slope-reversal.},
doi = {10.1063/1.4932006},
journal = {Physics of Plasmas},
number = 10,
volume = 22,
place = {United States},
year = {2015},
month = {10}
}