Abstract
In our previous statistical study of ULF fluctuations near the Moon connected to the foreshock, we found that these fluctuations can be characterized as a mixture of transverse and compressional wave modes with different properties at both locations. Our investigations reveal that the growth rate of waves depends on their mode being larger for compressive variations of the magnetic field strength and plasma density than for variations of magnetic field components.
Here, we compare the behavior of fluctuations around the Moon with the waves observed closer to the bow shock. We selected observations in the dayside foreshock between the bow shock and 30 RE.
Based on statistical studies from the THEMIS spacecraft, we discuss their properties, occurrence rates and a relation to solar wind and foreshock conditions. We conclude that compressional fluctuations are stronger in the quasi-perpendicular shock than in the quasiparallel shock.