Survey of coherent ion reflection at the quasi-parallel bow shock
- Los Alamos National Lab., NM (United States)
- Univ. of California, Los Angeles (United States)
Ions coherently reflected off the Earth's bow shock have previously been observed both when the upstream geometry is quasi-perpendicular and when it is quasi-parallel. In the case of quasiperpendicular geometry, the ions are reflected in a nearly specular manner and are quickly carried back into the shock by the convecting magnetic field. In the quasi-parallel geometry, however, near-specularly reflected ions' guiding center velocities would on the average be directed away from the shock, allowing the ions to escape into the upstream region. The conditions under which coherent reflection occurs and the subsequent coupling of the reflected ions to the incoming solar wind plasma are important factors when assessing the contribution of the reflected ions to the downstream temperature increase and the shock structure. The survey presented in this paper, along with previously reported observations, suggests that near-specularly reflected ions are indeed an important aspect of energy dissipation at the Earth's quasi-parallel bow shock. The authors find that (1) cool, coherent, near-specularly reflected ion beams are detected over nearly the full range of upstream plasma paraameters commonly found at the Earth's bow shock; (2) the beams are typically observed only near the shock ramp or some shock-like feature; and (3) the observed beam velocities are almost always consistent with what one would expect for near-specularly reflected ions after only a small fraction of a gyroperiod following reflection. The second and third points indicate that the beams spread very quickly in velocity space. This spread in velocities could be due either to interactions between the beam and incoming solar wind ions or to some initially small velocity spread in the beam.
- OSTI ID:
- 5222159
- Journal Information:
- Journal of Geophysical Research; (United States), Vol. 95:A3; ISSN 0148-0227
- Country of Publication:
- United States
- Language:
- English
Similar Records
Observational evidence on the origin of ions upstream of the earth's bow shock
ION ACCELERATION AT THE QUASI-PARALLEL BOW SHOCK: DECODING THE SIGNATURE OF INJECTION
Related Subjects
GENERAL PHYSICS
EARTH MAGNETOSPHERE
SOLAR WIND
IONS
REFLECTION
INTERACTIONS
COMPUTERIZED SIMULATION
ENERGY LOSSES
GEOMETRY
GUIDING-CENTER APPROXIMATION
ION BEAMS
ORIENTATION
SHOCK WAVES
BEAMS
CHARGED PARTICLES
EARTH ATMOSPHERE
LOSSES
MATHEMATICS
SIMULATION
SOLAR ACTIVITY
640201* - Atmospheric Physics- Auroral
Ionospheric
& Magetospheric Phenomena