HR: 08:45h
AN: SM21C-04    [Abstracts]
TI: A Statistical Survey of the ULF Spectrum and Wave Characteristics Observed by the Polar and ISEE Satellites
AU: * Chi, P J
EM: pchi@igpp.ucla.edu
AF: UCLA, Institute of Geophysics and Planetary Physics, Box 951567, Los Angeles, CA 90095-1567 United States
AU: Russell, C T
EM: ctrussell@igpp.ucla.edu
AF: UCLA, Institute of Geophysics and Planetary Physics, Box 951567, Los Angeles, CA 90095-1567 United States
AB: In this study we analyze the statistical properties of the wave spectrum in the Ultra-low-frequency (ULF) band by using the magnetometer data collected by Polar and ISEE satellites. The combined dataset consists of more than 25 years of observations covering a large portion of the magnetosphere, and therefore they provide the empirical knowledge of ULF wave characteristics as well as their spatial and temporal variations. In order to conduct the statistical analysis, two useful databases of the ULF waves are generated: (1) the spectral density in the ULF band, and (2) a catalog of the ULF wave events selected by applying a statistical criterion on the wave spectrum obtained in (1). Wavelet analysis is used in producing the two databases because of its computational efficiency. The catalog of ULF waves consists of the events whose waves are more monochromatic, and it is useful for identifying the occurrence of different types of ULF waves as well as understanding their generation mechanisms. Initial results show that the compressional Pc~3 waves occur more often in the subsolar region of the magnetosphere, consistent with the model of which the upstream waves being the source, whereas some compressional Pc~5 waves are found at high-latitude regions, possibly associated with the surface waves on the magnetospheric boundary. For the transverse component of the Pc~3-5 waves, the wave frequency decreases statistically with the $L$-value, in agreement with with the field line resonance effects. The wave catalog can also facilitate the selection of interesting events for in-depth studies. On the other hand, the wave spectrum database provides a useful input to the research of particle energization in the radiation belt, for which a simplified formula for the ULF spectrum is broadly assumed because of the limitations in observations. Our study also attempts to define a standard of fast generation of ULF wave databases so that similar computer algorithms can be applied to the electromagnetic field data acquired by future satellite missions.
DE: 2720 Energetic particles, trapped
DE: 2730 Magnetosphere--inner
DE: 2731 Magnetosphere--outer
DE: 2752 MHD waves and instabilities
DE: 2794 Instruments and techniques
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting