ULF waves play a central role in the dynamics of the inner magnetosphere. They are thought to be an important mechanism for energy transfer from the solar wind to magnetosphere and for accelerating and scattering higher energy particles in the radiation belts. They can also result in adverse space weather effects, such as errors in GPS signals, enhanced Joule heating, and geomagnetically-induced currents. The generation of magnetospheric ULF waves remains however an outstanding question in the field. Particularly problematic are magnetospheric ULF waves that are externally driven. Part of these waves originate in the foreshock and are transmitted into the inner magnetosphere. There are however very few studies tracking these waves and analysing their properties across the different regions of geospace.
The aim of our ISSI team is to advance significantly our understanding of the foreshock-driven magnetospheric ULF waves. We will study in a global manner their transmission across the foreshock-magnetosheath-magnetosphere system, using a combination of spacecraft and ground-based measurements and numerical simulations. Our work will focus on the detailed analysis of several events, corresponding to different solar wind conditions and levels of geomagnetic activity. This observational study will be complemented with a numerical study using the Vlasiator simulation code. Vlasiator provides global simulations of the magnetosphere while retaining ion kinetic processes, and is thus an ideal tool to investigate the transmission of foreshock waves across geospace.
More specifically, we will seek answers to the following science questions, centred around three topics:
(1) ULF waves in the magnetosheath
- How are foreshock ULF waves transmitted into the magnetosheath?
- What are their properties inside this region?
(2) ULF waves in the magnetosphere
- How does the wave energy enter and propagate in the magnetosphere?
- What effects do the ULF waves have on radiation belt electrons?
- How is the transmission of ULF waves modified during magnetic storms?
- What effect does the IMF strength have on this transmission?