HR: 1340h
AN: SM23A-0496    [Abstracts]
TI: AKR rain: A study of periodically modulated narrow-band drifting AKR emission observed with the Cluster WBD instrument
AU: * Mutel, R L
EM: robert-mutel@uiowa.edu
AF: The University of Iowa, Department of Physics and Astronomy, Iowa City, IA 52242 United States
AU: Menietti, J D
EM: jdm@space.physics.uiowa.edu
AF: The University of Iowa, Department of Physics and Astronomy, Iowa City, IA 52242 United States
AU: Christopher, I
EM: ivar-christopher@uiowa.edu
AF: The University of Iowa, Department of Physics and Astronomy, Iowa City, IA 52242 United States
AB: We have studied a peculiar type of AKR emission detected at 125, 250, and 500 kHz using the WBD instrument on the Cluster spacecraft. The emission ('rain') is characterized by a series of extremely narrowband (50 Hz or less) bursts drifting downward in frequency between 3-12 kHz/sec and often strongly amplitude modulated with a frequency separation 150-250 Hz. Assuming the emission can be identified with the local gyrofrequency, each burst corresponds to a localized emitter of dimension 1 km or less (about 10 Debye lengths) traveling upward along a magnetospheric field line with a speed 200-300 km/sec. Since this speed range corresponds to the local ion acoustic speed, we ascribe the emission to EMIC waves which excite localized AKR emission. We use simultaneous observations of 'rain' bursts from multiple spacecraft to determine the angular distribution of individual bursts.
DE: 7867 Wave/particle interactions
DE: 2772 Plasma waves and instabilities
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting