Simulation studies of electron acceleration by ion ring distributions in solar flares

K. G. McClements, J. J. Su, R. Bingham, J. M. Dawson, D. S. Spicer

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

Using a 2 1/2-D fully relativistic electromagnetic particle-in-cell code (PIC) we have investigated a potential electron acceleration mechanism in solar flares. The free energy is provided by ions which have a ring velocity distribution about the magnetic field direction. Ion rings may be produced by perpendicular shocks, which could in turn be generated by the super-Alfvénic motion of magnetic flux tubes emerging from the photosphere or by coronal mass ejections (CMEs). Such ion distributions are known to be unstable to the generation of lower hybrid waves, which have phase velocities in excess of the electron thermal speed parallel to the field and can, therefore, resonantly accelerate electrons in that direction. The simulations show the transfer of perpendicular ion energy to energetic electrons via lower hybrid wave turbulence. With plausible ion ring velocities, the process can account for the observationally inferred fluxes and energies of non-thermal electrons during the impulsive phase of flares. Our results also show electrostatic wave generation close to the plasma frequency: we suggest that this is due to a bump-in-tail instability of the electron distribution.
LanguageEnglish
Pages229-241
Number of pages13
JournalSolar Physics
Volume130
Issue number1-2
DOIs
Publication statusPublished - Dec 1990

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electron acceleration
solar flares
electron
ion
rings
simulation
ions
electrons
electrostatic waves
ion distribution
wave generation
coronal mass ejection
plasma frequencies
photosphere
electron distribution
phase velocity
flares
energy
magnetic flux
emerging

Keywords

  • electromagnetic particle-in-cell code
  • solar flares
  • electron acceleration
  • ion rings
  • wave generation

Cite this

McClements, K. G. ; Su, J. J. ; Bingham, R. ; Dawson, J. M. ; Spicer, D. S. / Simulation studies of electron acceleration by ion ring distributions in solar flares. In: Solar Physics. 1990 ; Vol. 130, No. 1-2. pp. 229-241.
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abstract = "Using a 2 1/2-D fully relativistic electromagnetic particle-in-cell code (PIC) we have investigated a potential electron acceleration mechanism in solar flares. The free energy is provided by ions which have a ring velocity distribution about the magnetic field direction. Ion rings may be produced by perpendicular shocks, which could in turn be generated by the super-Alfv{\'e}nic motion of magnetic flux tubes emerging from the photosphere or by coronal mass ejections (CMEs). Such ion distributions are known to be unstable to the generation of lower hybrid waves, which have phase velocities in excess of the electron thermal speed parallel to the field and can, therefore, resonantly accelerate electrons in that direction. The simulations show the transfer of perpendicular ion energy to energetic electrons via lower hybrid wave turbulence. With plausible ion ring velocities, the process can account for the observationally inferred fluxes and energies of non-thermal electrons during the impulsive phase of flares. Our results also show electrostatic wave generation close to the plasma frequency: we suggest that this is due to a bump-in-tail instability of the electron distribution.",
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Simulation studies of electron acceleration by ion ring distributions in solar flares. / McClements, K. G.; Su, J. J.; Bingham, R.; Dawson, J. M.; Spicer, D. S.

In: Solar Physics, Vol. 130, No. 1-2, 12.1990, p. 229-241.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Simulation studies of electron acceleration by ion ring distributions in solar flares

AU - McClements, K. G.

AU - Su, J. J.

AU - Bingham, R.

AU - Dawson, J. M.

AU - Spicer, D. S.

PY - 1990/12

Y1 - 1990/12

N2 - Using a 2 1/2-D fully relativistic electromagnetic particle-in-cell code (PIC) we have investigated a potential electron acceleration mechanism in solar flares. The free energy is provided by ions which have a ring velocity distribution about the magnetic field direction. Ion rings may be produced by perpendicular shocks, which could in turn be generated by the super-Alfvénic motion of magnetic flux tubes emerging from the photosphere or by coronal mass ejections (CMEs). Such ion distributions are known to be unstable to the generation of lower hybrid waves, which have phase velocities in excess of the electron thermal speed parallel to the field and can, therefore, resonantly accelerate electrons in that direction. The simulations show the transfer of perpendicular ion energy to energetic electrons via lower hybrid wave turbulence. With plausible ion ring velocities, the process can account for the observationally inferred fluxes and energies of non-thermal electrons during the impulsive phase of flares. Our results also show electrostatic wave generation close to the plasma frequency: we suggest that this is due to a bump-in-tail instability of the electron distribution.

AB - Using a 2 1/2-D fully relativistic electromagnetic particle-in-cell code (PIC) we have investigated a potential electron acceleration mechanism in solar flares. The free energy is provided by ions which have a ring velocity distribution about the magnetic field direction. Ion rings may be produced by perpendicular shocks, which could in turn be generated by the super-Alfvénic motion of magnetic flux tubes emerging from the photosphere or by coronal mass ejections (CMEs). Such ion distributions are known to be unstable to the generation of lower hybrid waves, which have phase velocities in excess of the electron thermal speed parallel to the field and can, therefore, resonantly accelerate electrons in that direction. The simulations show the transfer of perpendicular ion energy to energetic electrons via lower hybrid wave turbulence. With plausible ion ring velocities, the process can account for the observationally inferred fluxes and energies of non-thermal electrons during the impulsive phase of flares. Our results also show electrostatic wave generation close to the plasma frequency: we suggest that this is due to a bump-in-tail instability of the electron distribution.

KW - electromagnetic particle-in-cell code

KW - solar flares

KW - electron acceleration

KW - ion rings

KW - wave generation

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JO - Solar Physics

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