The role of transient ion foreshock phenomena in driving Pc5 ULF wave activity

The ion foreshock is a source of energy for magnetospheric ULF waves, but it is usually only considered effective at driving ULF waves with frequencies above the Pc5 (2–7 mHz) range. We present observations for an 8 h high speed solar wind interval on 14 July 2008 during which three distinct types of transient ion foreshock phenomena (TIFP) were observed just upstream of the dayside bow shock. We demonstrate that TIFP generate global magnetospheric Pc5 ULF waves with amplitudes as large as 10 mV/m in the electric field and 10 nT in the magnetic field. We characterize the magnetospheric ULF response to several different TIFP that occur during this interval, including the first report of the ULF response to a foreshock bubble. Using a novel spacecraft configuration, we find that the local time with the highest Pc5 wave amplitude is closely related to the location of the ion foreshock. Statistical studies of Pc5 ULF wave activity, other case studies of ULF waves driven by processes in the ion foreshock, and recent theoretical and simulation work on TIFP place these results in context: TIFP are an important energy source for Pc5 ULF waves in the magnetosphere.