Exploring the particle-wave coupling during intervals of the distant upstream ion foreshock: up to the first Earth's Lagrange (L1).

Several events have been identified of an ion foreshock extending up to 250 RE upstream of the Earth. These events occur mostly during periods of slowly drifting radial interplanetary magnetic field (IMF) when the 1-min average values of the strengths of the IMF and the solar wind (SW) speeds are mostly steady (Berdichevsky et al., 1999*). Here we study the frequency content, the polarization and the particle-wave coupling using a cross-spectrum analysis. We do a qualitative analysis of the origin of this wave-activity using the linear theory of plasma instabilities and explore the possibility of trapping of these strongly scattered particle fluxes. In this study we present results for observations on June 11, July 13, and Aug 25, 1995. For the study we use sampling times of waves and electron data of 12 sec or higher resolution energetic particle data. Solar wind plasma and magnetic field are collected by the MFI, SWE, WAVES, and 3DP instruments on Wind, and MGF and EPIC in GEOTAIL spacecraft. The spectral technique used is based on a set of Instrisic Modes resulting from an Emperical Decomposition Method inspired by the EMD method developed by Huang (Huang et al., 1998**) *Berdichevsky, D., G. Thejappa, R. Fitzenreiter, R. Lepping, T. Yamamoto, S. Kokubun, R. McEntire, D. Williams, and R.P. Lin, Widely spaced wave-particle observations during GEOTAIL and WIND magnetic conjunctions in the Earth's ion foreshock, J. Geophys. Res., 104, 463-482, 1999 **Huang, NE, Sheng, S, Long, SR, A new view of nonlinear water waves: The Hilbert Spectrum, Annu. Rev. Fluid Mech., 1999, 31, 417-57