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Title: Inferring Magnetospheric Heavy Ion Density using EMIC Waves

We present a method to infer heavy ion concentration ratios from EMIC wave observations that result from ionion hybrid (IIH) resonance. A key feature of the ion-ion hybrid resonance is the concentration of wave energy in a field-aligned resonant mode that exhibits linear polarization. This mode converted wave is localized at the location where the frequency of a compressional wave driver matches the IIH resonance condition, which depends sensitively on the heavy ion concentration. This dependence makes it possible to estimate the heavy ion concentration ratio. In this letter, we evaluate the absorption coefficients at the IIH resonance at Earth's geosynchronous orbit for variable concentrations of He+ and field-aligned wave numbers using a dipole magnetic field. Although wave absorption occurs for a wide range of heavy ion concentrations, it only occurs for a limited range of field-aligned wave numbers such that the IIH resonance frequency is close to, but not exactly the same as the crossover frequency. Using the wave absorption and observed EMIC waves from GOES-12 satellite, we demonstrate how this technique can be used to estimate that the He+ concentration is around 4% near L = 6.6.
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Resource Type:
Technical Report
Research Org:
Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Contributing Orgs:
1 Princeton Plasma Physics Laboratory, Princeton, NJ 08543, USA 2 Institute for Fusion Studies, University of Texas at Austin, TX 78712, USA 3 Center for Electromechanics, University of Texas at Austin, TX 78758, USA 4 ITER-India/Institute for Plasma Research, Bhat 382428, Gandhinagar, India 5 University of Maryland, College Park, MD 20742, USA 6 Virginia Diodes, Inc. Charlottesville, VA 22902, USA 7 Plasma Science and Fusion Center, MIT, Cambridge, MA 02139, USA 8 ITER Organization, Route de Vinon sur Verdon, 13115, St Paul Lez Durance, France
Country of Publication:
United States