Oblique whistler instability in the earth's foreshock

Journal Article · Tue Mar 01 04:00:00 EST 1983 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JA088iA03p02048· OSTI ID:6302039

Sentman, D D; Thomsen, M F; Gary, S P; Feldman, W C; Hoppe, M M

The linear Vlasov stability properties of electron velocity distributions, similar to those observed in the upstream foreshock region in association with obliquely propagating whistler waves at approximately 1 Hz, are studied. These distributions are modeled by a sum of bi-Maxwellians with drift speeds parallel to the magnetic field B. We find such distributions to be stable to modes with wavevectors k parallel to B but unstable to whistler waves propagating obliquely to the magnetic field. The frequencies and wavelengths of these unstable modes agree well with those of whistlers observed upstream of the earth's bow shock. The free energy source driving the instability is a region of positive parallel slope partialf/sub e//partialv/sub parallel/>0 at large pitch angles (about 85/sup 0/) and intermediate energies (about 20 eV), probably corresponding to the solar wind electrons magnetostatically reflected from the magnetic ramp of the bow shock. The whistlers grow via electromagnetic Landau resonance with this free energy source.

• Research Organization: Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90024
• OSTI ID: 6302039
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 88:A3; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640203* -- Atmospheric Physics-- Magnetospheric Phenomena-- (-1987)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
DISTRIBUTION FUNCTIONS
EARTH ATMOSPHERE
ELECTROMAGNETIC RADIATION
ELECTRON DENSITY
ELECTRON DRIFT
FUNCTIONS
INSTABILITY
MAGNETOSPHERE
NOISE
PLASMA INSTABILITY
RADIATIONS
RADIO NOISE
RADIOWAVE RADIATION
REFLECTION
SHOCK WAVES
SOLAR ACTIVITY
SOLAR WIND
WHISTLERS