Excitation of compressional waves and the formation of shocklets in the earth's foreshock

Journal Article · Fri May 01 04:00:00 EDT 1987 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JA092iA05p04423· OSTI ID:6349180

Hada, T; Kennel, C F; Teresawa, T

Large-amplitude waves with typical frequencies of 0.01--0.05 Hz are often observed in the foreshocks of earth and other planets. Large-amplitude waves in the earth's foreshock are sometimes (but not always) observed in a highly time-developed form, either as steepened pulses or as discrete oscillatory wave packets of finite length. This implies that nonlinearities are strong enough to modify their waveforms before the solar wind carries them out the foreshock. The instabilities and steepening of upstream waves in the earth's foreshock caused by backstreaming ions are discussed in the first part of the paper. For typical foreshock ''diffuse'' ion distributions, right and left-hand polarized(RHP and LHP) waves propagating parallel to the local magnetic field are preferentially excited. Such noncompressional waves neither steepen nor grow fast enough to account for the amplitude polarizations and waveforms observed in the diffuse ion foreshock. Oblique waves develop a density compression and their magnetic field polarization is elliptical. Although these characteristics match the observations of the steepened waves in the diffuse ion zone, the growth rates of those waves oblique enough to steepen are too small to account for observed amplitudes.

• Research Organization: Institute of Geophysics and Planetary Physics, Unvieristy of California at Los Angeles
• OSTI ID: 6349180
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 92:A5; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640201* -- Atmospheric Physics-- Auroral
Ionospheric
& Magetospheric Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
BACKSCATTERING
CHARGED PARTICLES
COMPRESSION
CYCLOTRON FREQUENCY
DAMPING
EARTH ATMOSPHERE
EARTH MAGNETOSPHERE
IONS
MAGNETIC FIELD CONFIGURATIONS
PLASMA WAVES
REFLECTION
SCATTERING
SHOCK WAVES
SOLAR ACTIVITY
SOLAR WIND
WAVE FORMS
WAVE PROPAGATION