Magnetohydrodynamic Wave-Associated Plasma Density Fluctuations in the Earth's Foreshock Region

Twenty episodes of magnetohydrodynamic wave activity in the Earth's ion foreshock region have been analyzed. Fluctuations in the electron density and magnetic field were analyzed to identify the various linear and nonlinear plasma processes that may be occurring in this region. Correlations between the density and various magnetic field components were performed. One major finding is that the component of the magnetic field parallel to the mean field is strongly correlated with the density fluctuations over a wide variety of scales. In addition two distinct wave populations were seen to exist. These findings have been interpreted as being the result of nonlinear parametric instabilities acting on obliquely propagating MHD waves.