Evolution of ion distributions across the nearly perpendicular bow shock: specularly and non-specularly reflected-gyrating ions

Journal Article · Mon Aug 01 04:00:00 EDT 1983 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JA088iA08p06121· OSTI ID:5470530

Sckopke, N; Paschmann, G; Bame, S J; Gosling, J T; Russell, C T

Ion velocity space distributions measured with Los Alamos/Garching instruments on ISEE 1 and 2 across the earth's bow shock have revealed that the nearly perpendicular shock reflects some fraction of the incident solar wind ions over a wide range of Mach numbers (M/sub A/approx. =2.0-12.4). The relative density of the reflected ions varies from 1-3% of the solar wind density at M/sub A/roughly-equal2 to 15-25% at M/sub A/ = 8-12, in qualitative agreement with computer simulations and with predictions that indicate that such ions are needed to provide essential dissipation at the shock. These ions gyrate about B in the plasma rest frame with a speed of approx.2 v/sub i/n, where r/sub i/n is the normal component of the solar wind flow, and their density increases by approx.2 orders of magnitude at the foward end of the ''foot'' of the shock profile approx.0.7 ion gyroradii upstream from the shock ramp. This is substantial evidence that the bulk of these ions have been reflected at the shock in a nearly specular fashion. Depending on the shock geometry, some low numbers of reflected-gyrating ions are sometimes observed a few gyroradii ahead of the outer edge of the foot. Model calculations suggest that these additional ions are produced by non-specular reflection of a much smaller fraction of the incident solar wind. Downstream of the shock ramp, the secondary ions gyrate with a slightly higher speed, v/sub g/roughly-equal2.15 v/sub i/n, in the downstream rest frame. Individual groups of gyrating ions rapidly disperse in velocity space to form a high-energy torus centered at the bulk velocity of the distributions.

• Research Organization: Max-Planck-Institut fuer Physik und Astrophysik, Institut fuer Extraterrestriche Physik, 8046 Garching, Federal Republic of Germany
• OSTI ID: 5470530
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 88:A8; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640203* -- Atmospheric Physics-- Magnetospheric Phenomena-- (-1987)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
BACKSCATTERING
COMPUTERIZED SIMULATION
DISTRIBUTION FUNCTIONS
EARTH ATMOSPHERE
FUNCTIONS
INTERPLANETARY MAGNETIC FIELDS
INTERPLANETARY SPACE
ION DENSITY
MACH NUMBER
MAGNETIC FIELDS
MAGNETOSPHERE
REFLECTION
SCATTERING
SHOCK WAVES
SIMULATION
SOLAR ACTIVITY
SOLAR WIND
SPACE
VELOCITY