HR: 11:00h
AN: SM12A-03 INVITED     [Abstracts]
TI: Mass Density Inferred From Toroidal Wave Frequencies And its Comparison to Electron 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: Dept Physics & Astronomy, Dartmouth College, 6127 Wilder Laboratory, Hanover, NH 03755-3528 United States
AU: Anderson, R R
EM: roger-r-anderson@uiowa.edu
AF: Department of Physics and Astronomy, University of Iowa, 615 Van Allen Hall, Iowa City, IA IA 52242 United States
AU: Hughes, W J
EM: hughes@bu.edu
AF: Department of Astronomy, Boston University, 725 Commonwealth Avenue, Boston, MA 02215 United States
AB: The frequency of standing Alfven waves depends on the plasma mass density and this fact has been used since the late 1950s to infer the mass density from observed ULF waves. The technique is valuable in magnetospheric physics because particle experiments usually cannot determine the total ion mass density. The ULF technique was revitalized in the early 1990s when the cross phase technique was developed to provide accurate standing wave frequencies from observations on the ground. It is important to note that reliable conversion from the frequency to the density depends on a number of factors. First, the field line configuration needs to be known. Second, a functional form needs to be given for the variation of the mass density along the field line. Third, the harmonic number of the observed waves needs to be determined. Concerning these factors, spacecraft observations have several advantages: the local magnetic field can be measured (although at a single point), multiharmonic toroidal waves are routinely detected to allow modeling of the mass density distribution along the field line, and the harmonic mode can be unambiguously determined using combined electric and magnetic field observations. In this presentation we use data from the CRRES satellite to illustrate the ULF technique during a period of high geomagnetic activity. We discuss the contribution of heavy ions to the storm time ring current by comparing inferred values of the mass density from the ULF technique with values of the electron number density inferred from plasma wave data.
DE: 2487 Wave propagation (6934)
DE: 2752 MHD waves and instabilities
DE: 2768 Plasmasphere
DE: 2788 Storms and substorms
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting