Low frequency waves observed by Interball-1 in foreshock and magnetosheath Original Research Article

Solar wind parameters in the magnetosheath and foreshock fluctuate over time scales from less than one second to hours with amplitudes as high as 100%. We investigate such variations using ion flux and magnetic field measurements with 1 s time resolution from the Interball-1 spacecraft. WIND and Geotail spacecraft were used to monitor the unperturbed solar wind. Fast magnetosonic waves dominate in the foreshock region with correlation coefficients between the ion flux and magnetic field magnitude r(F/B) > 0.7. In the magnetosheath, the plasma flow is mainly turbulent and the character of the turbulence is strongly controlled by the angle ΘBn between the bow shock normal and the interplanetary magnetic field direction. Behind quasi-parallel bow shocks (ΘBn < 45°), variations of the ion flux and magnetic field strongly increase. As the magnetosheath is a very inhomogeneous, anisotropic medium sensitive to the external conditions, different types of MHD-modes can be observed. Behind the quasi-perpendicular bow shock, mirror-mode waves are sometimes observed in the middle of the magnetosheath and near the magnetopause.