MMS observations of wave activity in the particle foreshock bubble foreshock region

Foreshock bubbles (FBs) are kinetic transient phenomena formed due to the interaction between IMF discontinuities and backstreaming energetic ions in Earth’s foreshock region. FBs can be driven by both rotational discontinuities and tangential discontinuities and are typically observed under higher solar wind speed conditions. They play important roles in the solar wind-magnetosphere coupling because of very large dynamic pressure variations associated with them. The trailing edge of an FB is usually a fast shock which forms due to the expansion of the thermal plasma in the core. Using data from Magnetospheric Multiscale (MMS) mission, we investigate an FB structure with a particle foreshock region upstream its trailing edge. Distinct wave activity is observed in the particle foreshock region and wave analysis shows that the waves with periods of a few seconds may be generated by shock-reflected ion instabilities. The ions reflected at FB shock are observed and the acceleration mechanism needs to be analyzed.