MPS Seminar: What do we know about interplanetary shocks? (Xochitl Blanco-Cano)

Interplanetary (IP) shocks are key structures in the solar wind, driven by fast coronal mass ejections and interactions between different solar wind streams. These shocks play a crucial role in processes such as particle acceleration, solar wind heating, and plasma compression throughout the heliosphere. In this talk, we will explore the fundamental properties of IP shocks observed by different missions. We will also present an interesting complex event observed by Solar Orbiter on March 8th 2022 at 0.5 AU, where the interaction between two interplanetary coronal mass ejections (ICMEs) drove a forward and a reverse shock with similarities to those bounding stream interaction regions (SIRs). Analysis of the microstructure of this event shows that wave characteristics change from one ICME to the other. Inside the first ICME waves have a broad band spectrum. In contrast, there are regions in the second ICME with very monochromatic waves. In both cases, waves are associated with proton and alpha particle distributions that show a super-Alfvenic drift, suggesting local wave generation. Larger amplitude waves due to ion reflection are found upstream of the forward shock forming an extended foreshock. Of particular interest is the fact that monochromatic ion cyclotron waves associated with anisotropic (Tperp >Tpar) ion distributions are found in the region between the two ICMEs. Our results show how ICME-ICME interaction can result in regions with a variety of microstructure phenomena in the inner heliosphere.