Abstract
Low-frequency (ULF) waves fill most of the upstream region that is connected to the bow shock by the interplanetary magnetic field (IMF) lines. The foreshock waves are generated by ion beam instability excited by counter-streaming flows of the incident and reflected ions.
However, the Moon coupled to its wake is a large obstacle that can affect the trajectory of energetic particles. Our previous global statistical study over nine years shows that waves could be growing as well as decaying towards the bow shock under the quasi-radial magnetic field.
In this work, we investigate the influence of the lunar wake on the activity of ULF waves in the Earth’s foreshock for the same IMF condition. We chose a statistical approach to compare two sets of data (global and effect of the lunar wake) with motivation to estimate factors influencing the growth rate of ULF fluctuations near the Moon and lunar wake.
We study the conditions for growing and damped fluctuations under different solar wind parameters. With this information, we discuss the role and importance of the different trajectories of wave propagation through the lunar wake and possible mechanisms that can lead to the observed results.