Suprathermal ions upstream from interplanetary shocks

Journal Article · Sun Jul 01 04:00:00 EDT 1984 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JA089iA07p05409· OSTI ID:6581727

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

Suprathermal ions with energies between solar wind thermal energies and approx.29 keV are occasionally observed ahead of outward propagating interplanetary shocks with the Los Alamos/Garching fast plasma experiment on ISEE 1 and 2. Compared with suprathermal ion velocity distributions observed upstream from the earth's bow shock, the upstream interplanetary shock ion velocity distributions are relatively structureless, and the particle fluxes are less intense. Typically the suprathermal ion distribution emerges smoothly from the solar wind thermal distribution and is nearly isotropic in the solar wind frame. Such distributions are observed with the fast plasma experiment only in association with interplanetary shocks. Field-aligned beams, kidney-bean-shaped distributions, shells of ions in velocity space, and bunches of gyrating ions-all common to the upstream region of the earth's bow shock-have not been observed ahead of interplanetary shocks. Highly structured ion velocity distributions observed upstream of the earth's bow shock apparently are caused directly or indirectly by the nearly specular reflection of solar wind ions at the shock, a consequence of the generally high Mach number of the solar wind flow at 1 AU. By way of contrast, most interplanetary shocks at 1 AU have low, subcritical Mach numbers, and solar wind ion reflection at these shocks does not appear to play a role in producing upstream suprathermal ion distributions at 1 AU. Nevertheless, solar wind ions are accelerated to high energies at interplanetary shocks. Leakage of shocked thermal plasma across these low-Mach-number shocks from the downstream region may play an important role in producing upstream suprathermal ion populations and may therefore constitute the first step in the acceleration of solar wind ions to high energies at these shocks.

• Research Organization: University of California, Los Alamos National Laboratory
• OSTI ID: 6581727
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 89:A7; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640107* -- Astrophysics & Cosmology-- Planetary Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ACCELERATION
DISTRIBUTION FUNCTIONS
EXPLORER SATELLITES
FUNCTIONS
INTERPLANETARY SPACE
PLASMA ACCELERATION
RADIATIONS
SATELLITES
SHOCK WAVES
SOLAR ACTIVITY
SOLAR PARTICLES
SOLAR RADIATION
SOLAR WIND
SPACE
STELLAR RADIATION