GEM: Sources of Electron Populations in the Plasma Sheet

Earth's magnetotail region is filled with charged particles from the solar wind and the terrestrial ionosphere, forming the plasma sheet. The research focuses on answering why the plasma sheet electrons are observed in the way they are and where they come from. The team will develop a data-based model (including empirical relations) of multiple electron population characteristics in the near-Earth plasma sheet. A female principal investigator will lead this project, expanding participation among underrepresented groups. The heavy involvement of a postdoc will promote training and learning opportunities for the early-career workforce. Results from this project are intended to be incorporated into existing courses at the University of Michigan and disseminated via presentations in the classroom, scientific meetings, and publication. The primary objective of this effort is to define the sources of multiple electron populations in the near-Earth plasma sheet (6-12 RE) and their roles in forming specific shapes of electron distribution functions using inter-calibrated THEMIS ESA and SST data from the whole period of operation. Multiple electron populations with different temperatures may indicate the different sources, e.g., the mantle particles entering through the distant tail and the magnetosheath particles entering through the flank magnetopause, ionosphere outflow. Different populations can have different anisotropy. When the sources of electron populations are known, the modeling of them becomes more achievable. As a product of the investigation, a data-based model (including empirical relations) of multiple electron population characteristics in the near-Earth plasma sheet (moments and fluxes) parameterized by the solar wind, IMF parameters, geomagnetic activity indices, and ionosphere parameters (e.g., polar cap potential) will be developed. Obtaining a detailed picture of the electron population in the near-Earth plasma sheet is important and of high scientific priority. The detailed analysis of the electron data provided by THEMIS spacecraft outside the geostationary distances in the near-Earth plasma sheet is a unique investigation and, at the same time, complementary to the ongoing studies with other data, such as, for example, Van Allen Probes data. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.