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Title: Formation of collisionless shocks in magnetized plasma interaction with kinetic-scale obstacles

Abstract

We investigate the formation of collisionless magnetized shocks triggered by the interaction between magnetized plasma flows and miniature-sized (order of plasma kinetic-scales) magnetic obstacles resorting to massively parallel, full particle-in-cell simulations, including the electron kinetics. The critical obstacle size to generate a compressed plasma region ahead of these objects is determined by independently varying the magnitude of the dipolar magnetic moment and the plasma magnetization. Here we find that the effective size of the obstacle depends on the relative orientation between the dipolar and plasma internal magnetic fields, and we show that this may be critical to form a shock in small-scale structures. We also study the microphysics of the magnetopause in different magnetic field configurations in 2D and compare the results with full 3D simulations. Finally, we evaluate the parameter range where such miniature magnetized shocks can be explored in laboratory experiments.

Authors:
ORCiD logo [1];  [2];  [3];  [4]; ORCiD logo [5]; ORCiD logo [1]
  1. Univ. of Lisbon (Portugal). Inst. Superior Tecnico, Inst. of Plasmas and Nuclear Fusion, Group for Lasers and Plasmas (GoLP)
  2. Univ. of Lisbon (Portugal). Inst. Superior Tecnico, Inst. of Plasmas and Nuclear Fusion, Group for Lasers and Plasmas (GoLP); SLAC National Accelerator Lab., Menlo Park, CA (United States)
  3. Science and Technology Facilities Council (STFC), Oxford (United Kingdom). Rutherford Appleton Lab. (RAL)
  4. Science and Technology Facilities Council (STFC), Oxford (United Kingdom). Rutherford Appleton Lab. (RAL); Univ. of Strathclyde, Glasgow, Scotland (United Kingdom)
  5. Univ. of Lisbon (Portugal). Inst. Superior Tecnico, Inst. of Plasmas and Nuclear Fusion, Group for Lasers and Plasmas (GoLP); Univ. of Lisbon (Portugal). Inst. Univ. de Lisboa (ISCTE-IUL), Dept. of Information Science and Technology (DCTI)
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1353106
Grant/Contract Number:
ERC-2015-AdG 695088; AC02-76SF00515
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 24; Journal Issue: 2; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; mini magnetospheres; collisionless shocks; space physics; PIC simulations

Citation Formats

Cruz, F., Alves, E. P., Bamford, R. A., Bingham, R., Fonseca, R. A., and Silva, L. O. Formation of collisionless shocks in magnetized plasma interaction with kinetic-scale obstacles. United States: N. p., 2017. Web. doi:10.1063/1.4975310.
Cruz, F., Alves, E. P., Bamford, R. A., Bingham, R., Fonseca, R. A., & Silva, L. O. Formation of collisionless shocks in magnetized plasma interaction with kinetic-scale obstacles. United States. doi:10.1063/1.4975310.
Cruz, F., Alves, E. P., Bamford, R. A., Bingham, R., Fonseca, R. A., and Silva, L. O. Mon . "Formation of collisionless shocks in magnetized plasma interaction with kinetic-scale obstacles". United States. doi:10.1063/1.4975310. https://www.osti.gov/servlets/purl/1353106.
@article{osti_1353106,
title = {Formation of collisionless shocks in magnetized plasma interaction with kinetic-scale obstacles},
author = {Cruz, F. and Alves, E. P. and Bamford, R. A. and Bingham, R. and Fonseca, R. A. and Silva, L. O.},
abstractNote = {We investigate the formation of collisionless magnetized shocks triggered by the interaction between magnetized plasma flows and miniature-sized (order of plasma kinetic-scales) magnetic obstacles resorting to massively parallel, full particle-in-cell simulations, including the electron kinetics. The critical obstacle size to generate a compressed plasma region ahead of these objects is determined by independently varying the magnitude of the dipolar magnetic moment and the plasma magnetization. Here we find that the effective size of the obstacle depends on the relative orientation between the dipolar and plasma internal magnetic fields, and we show that this may be critical to form a shock in small-scale structures. We also study the microphysics of the magnetopause in different magnetic field configurations in 2D and compare the results with full 3D simulations. Finally, we evaluate the parameter range where such miniature magnetized shocks can be explored in laboratory experiments.},
doi = {10.1063/1.4975310},
journal = {Physics of Plasmas},
number = 2,
volume = 24,
place = {United States},
year = {Mon Feb 06 00:00:00 EST 2017},
month = {Mon Feb 06 00:00:00 EST 2017}
}

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  • The interaction of a laser-driven super-Alfvénic magnetic piston with a large, preformed magnetized ambient plasma has been studied by utilizing a unique experimental platform that couples the Raptor kJ-class laser system [Niemann et al., J. Instrum. 7, P03010 (2012)] to the Large Plasma Device [Gekelman et al., Rev. Sci. Instrum. 62, 2875 (1991)] at the University of California, Los Angeles. This platform provides experimental conditions of relevance to space and astrophysical magnetic collisionless shocks and, in particular, allows a detailed study of the microphysics of shock formation, including piston-ambient ion collisionless coupling. An overview of the platform and its capabilitiesmore » is given, and recent experimental results on the coupling of energy between piston and ambient ions and the formation of collisionless shocks are presented and compared to theoretical and computational work. In particular, a magnetosonic pulse consistent with a low-Mach number collisionless shock is observed in a quasi-perpendicular geometry in both experiments and simulations.« less
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  • Collisionless shocks are common phenomena in space and astrophysical systems, and in many cases, the shocks can be modeled as the result of the expansion of a magnetic piston though a magnetized ambient plasma. Only recently, however, have laser facilities and diagnostic capabilities evolved sufficiently to allow the detailed study in the laboratory of the microphysics of piston-driven shocks. We review experiments on collisionless shocks driven by a laser-produced magnetic piston undertaken with the Phoenix laser laboratory and the Large Plasma Device at the University of California, Los Angeles. The experiments span a large parameter space in laser energy, backgroundmore » magnetic field, and ambient plasma properties that allow us to probe the physics of piston-ambient energy coupling, the launching of magnetosonic solitons, and the formation of subcritical shocks. Here, the results indicate that piston-driven magnetized collisionless shocks in the laboratory can be characterized with a small set of dimensionless formation parameters that place the formation process in an organized and predictive framework.« less
  • Heating at collisionless shocks due to the kinetic cross-field streaming instability, which is the finite beta (ratio of plasma to magnetic pressure) extension of the modified two stream instability, is studied. Heating rates are derived from quasi-linear theory and compared with results from particle simulations to show that electron heating relative to ion heating and heating parallel to the magnetic field relative to perpendicular heating for both the electrons and ions increase with beta. The simulations suggest that electron dynamics determine the saturation level of the instability, which is manifested by the formation of a flattop electron distribution parallel tomore » the magnetic field. As a result, both the saturation levels of the fluctuations and the heating rates decrease sharply with beta. Applications of these results to plasma heating in simulations of shocks and the earth's bow shock are described.« less