We propose a team of 12 scientists to advance our current understanding of the importance of cold ionospheric plasma that is present in the Earth’s magnetosphere. Low energy (1 – 100 eV) light and heavy ions as well as electrons are known to escape from the ionosphere and populate most regions of the magnetosphere. Together with the solar wind, they are the main source of magnetospheric plasma, and there are a large number of studies addressing their occurrence and variability. Past studies have also demonstrated that ionospheric cold plasma is important to the global dynamics of the Earth’s magnetosphere. For instance, it constitutes a non-negligible fraction of the plasma density in the outer magnetosphere, where magnetic reconnection with the solar wind takes place, changing the reconnection rate between the solar wind and the Earth’s magnetosphere. Moreover, ionospheric outflows are an important source of cold plasma in the Earth’s magnetotail, where magnetic reconnection also occurs and a large amount of energy stored by magnetic fields is converted into kinetic energy of the ionospheric particles, which can then populate the plasma sheet and the ring current.

The Magnetospheric MultiScale (MMS) mission, launched by NASA in 2015, is capable of resolving the smallest scales of magnetospheric plasmas for the first time, including cold ion length-scales, which are smaller than hot ion length-scales owing to their smaller gyroradius, and electron length-scales. There are recent MMS observations at kinetic scales, both at the dayside magnetopause and magnetotail, of the cold plasma component interacting via magnetic reconnection with the magnetospheric and solar wind plasmas. These recent observations, supported by state-of-the-art Particle-In-Cell (PIC) simulations, are revealing new processes that initiate at the smallest scales, and that can have large-scale implications for magnetosphere dynamics.

This team will first compile the knowledge from more than 50 years of ionospheric plasma observations in the magnetosphere, with the purpose of inferring the global dynamics and characteristics of ionospheric plasma throughout the magnetosphere. Then, the team will use high-resolution MMS measurements in conjunction with most recent kinetic (PIC) simulations to study the microphysical effects that cold ions and electrons introduce to the plasma, with a particular focus on particle energization. Finally, the team will incorporate these findings to global ionosphere – magnetosphere – solar wind models that have been developed by team members during the last years. The actions described above will help the team to provide new understanding of the global magnetospheric dynamics and its coupling with the ionosphere and the solar wind, that can be implemented in magnetosphere and space weather models.

The team proposed here includes 12 scientists from 7 nationalities, involves 11 institutions and comprises experts of different domains, including spacecraft observations, kinetic PIC simulations and global magnetosphere modeling. We plan to have three meetings in two years: one at ESAC, Madrid, funded by the ESAC science faculty, and two at ISSI, Bern.