On the persistence of unstable bump-on-tail electron velocity distributions in the earth's foreshock

Journal Article · Thu Sep 01 04:00:00 EDT 1988 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JA093iA09p09628· OSTI ID:7066367

Klimas, A J; Fitzenreiter, R J

Further evidence for the persistence of bump-on-tail unstable reduced velocity distribution in the Earth's electron foreshock is presented. This persistence contradicts our understanding of quasi-linear saturation of the bump-on-tail instability; the distributions should be stabilized through velocity space diffusion too quickly to allow an observation of their unstable form. A modified theory for the saturation of the bump-on-tail instability in the Earth's foreshock is proposed and examined using numerical simulation and quasi-linear theoretical techniques. It is argued the mechanism due to Filbert and Kellogg and to Cairns which is responsible for the creation of the bump-on-tail velocity distribution in the foreshock is still operative during the evolution of the bump-on-tail instability. The saturated state of the plasma must represent a balance between this creation mechanism and velocity space diffusion; the saturated state is not determined by velocity space diffusion alone. Thus the velocity distribution of the saturated stat may still appear bump-on-tail unstable to standard linear analysis which does not take the creation mechanism into account. The bump-on-tail velocity distributions in the foreshock would then represent the state of the plasma after saturation of the bump-on-tail instability, not before.

• Research Organization: Laboratory for Extraterrestrial Physics, NASA Goddard Space Flight Center, Greenbelt, Maryland
• OSTI ID: 7066367
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 93:A9; 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
BOLTZMANN-VLASOV EQUATION
BUMP-IN-TAIL INSTABILITY
DEBYE LENGTH
DIFFERENTIAL EQUATIONS
DIMENSIONS
DISTRIBUTION FUNCTIONS
EARTH ATMOSPHERE
EARTH MAGNETOSPHERE
ELECTRON DENSITY
ELECTRON TEMPERATURE
ELECTRONS
ELEMENTARY PARTICLES
EQUATIONS
FERMIONS
FUNCTIONS
INSTABILITY
LENGTH
LEPTONS
PARTIAL DIFFERENTIAL EQUATIONS
PLASMA INSTABILITY
PLASMA MICROINSTABILITIES
SOLAR ACTIVITY
SOLAR WIND