HR: 0800h
AN: SH31A-1175    [Abstracts]
TI: Ion-Acoustic Instabilities in the Solar Wind
AU: * Gomberoff, L
EM: lgombero@uchile.cl
AF: Universidad de Chile, Las Palmeras 3425, NUNOA, Santiago, M 653 Chile
AU: Hoyos, J
EM: jhoyos@fisica.ciencias.uchile.cl
AF: Universidad de Chile, Las Palmeras 3425, NUNOA, Santiago, M 653 Chile
AB: It has been shown that ion-acoustic waves can be estabilized by finite amplitude left-hand polarized waves propagating in the direction of the external magnetic field [Gomberoff et al., 2004, J. Geophys. Res. 10(A0718),10.109/20004JA010466]. This result was shown to apply in plasma systems composed of electrons, protons and a proton beam. Later on, it was shown that the same instability is possible even in the absence of the proton beam [Gomberoff et al., 2004b J. Res. Lett. (submitted)]. It is shown here that the instability can actually be triggered quite generall by circularly polarized finite amplitude waves propagating either forward or backward relative to the external field. The instability occurs when the amplitude of the finite amplitude wave is larger than a threshold value. These waves are shown to have the properties of the ion-acoustic waves observed in the solar wind: (a) they do not seem to be Landau damped for proton temperatures larger that the electron temperatures, $T_p \geq T_{e}$, (b) they are more likely to occur closer to the Sun, and (c) the may exist independently of the proton beam velocity.
DE: 7500 SOLAR PHYSICS, ASTROPHYSICS, AND ASTRONOMY
DE: 7815 Electrostatic structures
DE: 7839 Nonlinear phenomena
DE: 7868 Wave/wave interactions
DE: 6984 Waves in plasma
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2004 AGU Fall Meeting