APERIODIC MAGNETIC TURBULENCE PRODUCED BY RELATIVISTIC ION BEAMS

Journal Article · Mon Feb 01 04:00:00 EST 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/709/2/1148· OSTI ID:21392274

Niemiec, Jacek ^[1]; Pohl, Martin ^[2]; Bret, Antoine ^[3]; Stroman, Thomas ^[4]

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1. Instytut Fizyki Jadrowej PAN, ul. Radzikowskiego 152, 31-342 Krakow (Poland)
2. Institut fuer Physik und Astronomie, Universitaet Potsdam, 14476 Potsdam-Golm (Germany)
3. ETSI Industriales, Universidad de Castilla-La Mancha, 13071 Ciudad Real (Spain)
4. Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States)

Magnetic-field generation by a relativistic ion beam propagating through an electron-ion plasma along a homogeneous magnetic field is investigated with 2.5D high-resolution particle-in-cell (PIC) simulations. The studies test predictions of a strong amplification of short-wavelength modes of magnetic turbulence upstream of nonrelativistic and relativistic parallel shocks associated with supernova remnants (SNRs), jets of active galactic nuclei, and gamma-ray bursts. We find a good agreement in the properties of the turbulence observed in our simulations compared with the dispersion relation calculated for linear waves with arbitrary orientation of k-vector. Depending on the parameters, the back-reaction on the ion beam leads to filamentation of the ambient plasma and the beam, which in turn influences the properties of the magnetic turbulence. For mildly and ultrarelativistic beams, the instability saturates at field amplitudes a few times larger than the homogeneous magnetic field strength. This result matches our recent studies of nonrelativistically drifting, hot cosmic-ray particles upstream of SNR shocks which indicated only a moderate magnetic-field amplification by nonresonant instabilities. We also demonstrate that the aperiodic turbulence generated by the beam can provide efficient particle scattering with a rate compatible with Bohm diffusion. Representing the ion beam as a constant external current, i.e., excluding a back-reaction of the magnetic turbulence on the beam, we observe nonresonant parallel modes with wavelength and growth rate as predicted by analytic calculations. In this unrealistic setup, the magnetic field is amplified to amplitudes far exceeding the homogeneous field, as observed in recent magnetohydrodynamic and PIC simulations.

• OSTI ID: 21392274
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 709; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
79 ASTRONOMY AND ASTROPHYSICS
ACCELERATION
AMPLIFICATION
AMPLITUDES
BEAMS
CHARGED PARTICLES
COSMIC GAMMA BURSTS
COSMIC RADIATION
COSMIC RADIO SOURCES
DISPERSION RELATIONS
ELECTRONS
ELEMENTARY PARTICLES
ENERGY RANGE
FERMIONS
GALAXY NUCLEI
INSTABILITY
ION BEAMS
IONIZING RADIATIONS
IONS
LEPTONS
MAGNETIC FIELDS
ORIENTATION
PLASMA
PRIMARY COSMIC RADIATION
RADIATIONS
RELATIVISTIC RANGE
RESOLUTION
SCATTERING
SHOCK WAVES
SIMULATION
SUPERNOVA REMNANTS
TURBULENCE