Local time dependence of ULF wave activity driven by interplanetary shocks and foreshock transients

Magnetospheric ultra-low frequency (ULF) waves are driven by multiple sources. In this study we focus on two sources: interplanetary (IP) shocks that are large-scale events and foreshock transients that are mesoscale events. The abrupt variations of interplanetary magnetic field (IMF) and solar wind parameters in IP shocks are known to generate Pc5 range (2-7 mHz) ULF waves in the magnetosphere. The impact angle – the angle between the Sun-Earth line and IP shock normal vector – has been observed to affect the generation of magnetospheric ULF waves. Discontinuities in the IMF can create transient phenomena in Earth's foreshock. The largest transient phenomena, foreshock bubbles and hot flow anomalies, have a core with low density and magnetic field strength and a boundary with enhanced density and field strength. These changes in the density can cause outward and inward motions of the magnetopause and thus generate Pc5 ULF waves in the magnetosphere. To get novel insights on how the ULF waves are distributed inside the magnetosphere, we use a new ground-based, 1-minute resolution, magnetic local time dependent Pc5 ULF index derived from SuperMAG data. We study the local time dependence of magnetospheric ULF waves generated by IP shocks and foreshock transients and whether this dependence is related to the impact angle of IP shocks and impact point of foreshock transients. In addition, this study assesses the suitability of the new index for studying the ULF wave activity driven by foreshock transients.