Earth’s magnetosphere dynamics during “forced breathing” due to solar wind periodic density structures

In the solar wind density, we often observe periodic fluctuations on time scales ranging from a few minutes to a few hours which we refer to as Periodic Density Structures (PDSs). The PDSs belong to the class of “meso-scale structures” with radial length scales greater than or equal to the size of the Earth’s dayside magnetosphere. The periodic character of these transients (≈0.2-4.0 mHz) can determine periodic compressional fluctuations of the Earth’s magnetic field at similar frequencies (“forced breathing” mode). The corresponding time scales overlap with the frequency range of Pc5 Ultra Low Frequency (ULF) waves (≈1.7-6.7 mHz). The compressional “forced breathing” fluctuations are often global and impact the entire Earth’s magnetosphere system/dynamics.  Using a recently developed spectral analysis approach applied to magnetic field observations at satellites and ground stations, we were able to differentiate directly driven magnetic field oscillations from Pc5 ULF waves triggered by other sources. Here, we discuss clear examples of such a directly driven process also showing effects on radiation belt electron dynamics and loss.