Hydromagnetic Wave Excitation Upstream of an Interplanetary Traveling Shock

Using data of the Highly Suprathermal Time-Of-Flight sensor of the Charge, Element, and Isotope Analysis System on board the Solar and Heliospheric Observatory spacecraft located at Lagrangian point L1 near Earth, we have measured proton spectra in the energy range 60 keV-2 MeV associated with the Bastille Day coronal mass ejection of 2000 July 14-16. For the same event, the power spectral densities of the magnetic field fluctuations in the solar wind have been measured with the magnetometer on board the Advanced Composition Explorer in the frequency range from about 0.05 mHz to 0.5 Hz. Within 0.11 AU upstream of the main shock, the flux of protons in the energy range 150 keV-2 MeV decreases much more rapidly with distance from the shock than is expected from diffusion in typical solar wind magnetic turbulence. In the same upstream region, the excitation of hydromagnetic waves in the frequency range 0.25-3 mHz and with power spectral density levels of up to 100 times the typical levels in the ambient solar wind is observed.