The importance of electrostatic ion-cyclotron instability for quiet-time proton auroral precipitation

Journal Article · Sat Jan 01 04:00:00 EST 1977 · Geophys. Res. Lett.; (United States)

DOI:https://doi.org/10.1029/GL004i001p00045· OSTI ID:7130612

Ashour-Abdalla, M; Thorne, R M

Even during geomagnetically quiet periods the loss cone distribution of energetic outer zone ions can provide sufficient free energy to excite quasi-electrostatic instability over a broad frequency range confined to bands centered between multiples of the ion gyrofrequency. Preliminary calculations of the wave growth near the lower cyclotron harmonics indicates that auroral zone (L approx. = 10) wave amplitudes should readily approach the nonlinear range. The expected frequency range together with nonlinear saturation arguments suggests that this instability may be related to the more or less continual presence of the recently reported 1--10 mV/m broad band electrostatic wave turbulence on auroral field lines. Such turbulence should cause strong diffusion scattering of the ambient ion population (1--100 keV); this would account for the persistent nocturnal proton auroral precipitation from field lines just within the outer boundary of trapping. The instability, however, may be severely suppressed by thermal electron (1--10 eV) Landau damping. It should therefore be less effective on the dayside (especially at lower L), and it is expected to be quenched entirely within the plasmasphere or detached plasma regions. (AIP)

• Research Organization: Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90024
• OSTI ID: 7130612
• Journal Information: Geophys. Res. Lett.; (United States), Journal Name: Geophys. Res. Lett.; (United States) Vol. 4:1; ISSN GPRLA
• Country of Publication: United States
• Language: English

Related Subjects

640201* -- Atmospheric Physics-- Auroral
Ionospheric
& Magetospheric Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
AURORAE
CHARGED-PARTICLE PRECIPITATION
CYCLOTRON INSTABILITY
DAMPING
EARTH ATMOSPHERE
INSTABILITY
INSTABILITY GROWTH RATES
LANDAU DAMPING
LOSS CONE
MAGNETOSPHERE
PLASMA INSTABILITY
PLASMA MICROINSTABILITIES
PLASMA WAVES
PROTON PRECIPITATION
TURBULENCE