Suprathermal He{sup 2+} in the Earth`s foreshock region

Journal Article · Fri Sep 01 04:00:00 EDT 1995 · Journal of Geophysical Research

DOI:https://doi.org/10.1029/95JA00898· OSTI ID:175830

Fuselier, S A ^[1]; Thomsen, M F ^[2]; Ipavich, F M ^[3]; Schmidt, W K.H. ^[4]

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1. Lockheed Palo Alto Research Lab., CA (United States)
2. Los Alamos National Lab., NM (United States)
3. Univ. of Maryland, College Park, MD (United States)
4. Max-Planck-Institut fuer Aeronomie, Katlenburg-Lindau (Germany)

ISEE 1 and 2 H{sup +} and He{sup 2+} observations upstream from the Earth`s bow shock are used to investigate the origin of energetic (or diffuse) ion distributions. Diffuse ion distributions have energies from a few keV/e to > 100 keV/e and have near solar wind concentrations (i.e., an average of about 4% He{sup 2+}). These distributions may evolve from suprathermal ion distributions that have energies between 1 and a few keV/e. Upstream intervals were selected from the ISEE data to determine which suprathermal distributions have He{sup 2+} concentrations similar to those of diffuse ion distributions. The type of distribution and the location in the foreshock were similar in all events studied. Two intervals that represent the results from this study are discussed in detail. The results suggest that diffuse ion distributions evolve from suprathermal distributions in the region upstream from the quasi-parallel bow shock. For He{sup 2+}, the suprathermal distribution is a nongyrotropic partial ring beam and has characteristics consistent with specular reflection off the quasi-parallel bow shock. The suprathermal proton distributions associated with these He{sup 2+} distributions are nongyrotropic partial ring beams or nearly gyrotropic ring beams also approximately consistent with specular reflection. The location in the quasi-parallel foreshock and the similarity of the suprathermal He{sup 2+} and H{sup +} distributions suggest that these are the seed population for diffuse distributions in the foreshock region. 30 refs., 5 figs., 1 tab.

• OSTI ID: 175830
• Journal Information: Journal of Geophysical Research, Journal Name: Journal of Geophysical Research Journal Issue: A9 Vol. 100; ISSN JGREA2; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
ACCELERATION
COLLISIONLESS PLASMA
DISTRIBUTION
HELIUM IONS
HYDROGEN IONS 1 PLUS
INTERPLANETARY MAGNETIC FIELDS
SHOCK WAVES
SOLAR WIND
THERMAL SHOCK