Propagation of Ultralow‐Frequency Waves from the Ion Foreshock into the Magnetosphere During the Passage of a Magnetic Cloud Journal of Geophysical Research: Space Physics

We have examined the properties of ultralow-frequency (ULF) waves in space (the ion foreshock, magnetosheath, and magnetosphere) and at dayside magnetometer stations (L = 1.6–6.5) during Earth's encounter with a magnetic cloud in the solar wind, which is characterized by magnetic fields with large magnitudes (∼14 nT) and small cone angles (∼30°). In the foreshock, waves were excited at ∼90 m Hz as expected from theory, but there were oscillations at other frequencies as well. Oscillations near 90 mHz were detected at the other locations in space, but they were not in general the most dominant oscillations. On the ground, pulsations in the approximate Pc2–Pc4 band (5 mHz–120 mHz)