HR: 17:15h
AN: SM44A-06    [Abstracts]
TI: Toroidal Harmonics Observed at The GOES 5 Spacecraft and Their Implication for the Field Line Distribution of Mass Density
AU: * Takahashi, K
EM: kazue.takahashi@jhuapl.edu
AF: Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723-6099 United States
AU: Denton, R E
EM: richard.e.denton@dartmouth.edu
AF: Dartmouth College, Dept Physics & Astronomy, Hanover, NH 03755-3528 United States
AB: Abstract. The relationship between the frequencies of standing Alfven wave harmonics depends on the distribution of mass along the magnetic field line that sustains the waves. This fact is the basis of inversion techniques to estimate the plasma mass density variation along the magnetic field using ULF waves. However, the multiharmonic technique has not been used extensively because it is difficult to accurately determine the frequencies. Data from geostationary satellites provide the best possibility for a successful implementation of the technique because these satellites accumulate the spectral information on the harmonics with minimal variations in frequency. We have statistically studied the frequency of multiharmonic toroidal waves detected by the GOES 5 geostationary satellite in 1986, during solar minimum. We quantify the relationship among the harmonics using the frequency ratio fn/f3, where fn is the frequency of the nth harmonic (n = 1 for the fundamental mode) and the third harmonic is chosen as the reference because it is the most ubiquitous mode at GOES 5. Using all data acquired in 1986 we find f1/f3 = 0.24, f2/f3, = 0.64, f4/f3 = 1.37, and f5/f3 = 1.73. These frequencies are consistent with a mass density distribution that is only slightly peaked at the magnetic equator as compared with the distribution previously inferred from frequencies measured by the CRRES spacecraft. The CRRES mission, however, took place during 1990 and 1991, which was at solar maximum. Results to date will be presented, including an examination of the inferred mass density distribution as a function of activity level.
DE: 2730 Magnetosphere: inner
DE: 2740 Magnetospheric configuration and dynamics
DE: 2752 MHD waves and instabilities (2149, 6050, 7836)
DE: 2753 Numerical modeling
DE: 2760 Plasma convection (2463)
SC: SPA-Magnetospheric Physics [SM]
MN: Fall Meeting 2005