Diffuse ions at a quasi-parallel collisionless shock: Simulations

Journal Article · Mon Oct 01 04:00:00 EDT 1990 · Geophysical Research Letters (American Geophysical Union); (United States)

DOI:https://doi.org/10.1029/GL017i011p01821· OSTI ID:5514967

Scholer, M ^[1]

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1. Max-Planck-Inst. fuer extraterrestrische Physik, Garching (West Germany)

Large scale one-dimensional hybrid simulations of a quasi-parallel ({Theta}{sub Bn} = 20{degree}) high Mach numbers (M{sub s} {approximately} 5) collisionless shock have been performed. The numerical system is 500 ion inertial lengths long and the shock has been followed up to 150 ion gyroperiods. The omnidirectional distribution function of the ions in the region upstream of the shock exhibits a high energy tail. About 5% of all ions in the upstream region have a velocity exceeding the shock ram velocity. Phase space contour plots show that these ions are diffuse. These ions are accelerated to high velocities during their first encounter with the shock. They stay very close to the shock for an extended period of time, about 50 gyroperiods, and experience the electric and magnetic field near the constantly reforming shock. Although the electric field at the particle position is highly fluctuating, the particle motion leads to a net energy gain. These particles may constitute a seed particle population for a first order Fermi process. The initial state of such a Fermi process can indeed be seen: some particles escape upstream, are turned back by the upstream waves and recross the shock, thus increasing their energy even further.

• OSTI ID: 5514967
• Journal Information: Geophysical Research Letters (American Geophysical Union); (United States), Journal Name: Geophysical Research Letters (American Geophysical Union); (United States) Vol. 17:11; ISSN GPRLA; ISSN 0094-8276
• Country of Publication: United States
• Language: English

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Ionospheric
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71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ACCELERATION
CHARGED PARTICLES
COMPUTERIZED SIMULATION
DISTRIBUTION FUNCTIONS
EARTH ATMOSPHERE
EARTH MAGNETOSPHERE
ELECTRIC FIELDS
FUNCTIONS
INTERACTIONS
IONS
MAGNETIC FIELDS
MATHEMATICAL MODELS
MATHEMATICAL SPACE
ONE-DIMENSIONAL CALCULATIONS
ORIGIN
PHASE SPACE
REFLECTION
SHOCK WAVES
SIMULATION
SOLAR ACTIVITY
SOLAR WIND
SPACE
VELOCITY