03/20/2026
By Lynne Schaufenbil
Title: Interplay of Sources in the Earth’s Plasma Sheet
Abstract:
How the plasma sheet forms is a fundamental question in magnetospheric physics. The plasma sheet population has contributions from both the ionosphere and the solar wind, but how the relative contributions from the two sources depend on driving conditions, and what transport paths the ions take to reach the plasma sheet are not fully known. One tool to determine the source is the ion composition. The solar wind is predominantly H+ with ~4% He++, while the ionospheric outflow also consists of significant H+, combined with ionospheric heavy ions dominated by O+. The appearance of O+ is a clear sign of an ionospheric contribution, but because both sources contain significant H+, it has been difficult to determine how much of the H+ comes from each source. It is well known that O+ in the plasma sheet increases during active times, indicating a strong ionospheric source during storms. Our recent work has focused on both determining the contribution of the solar wind source and on determining the pathways for ionospheric ions to reach the plasma sheet. Using plasma sheet data from MMS and solar wind composition data from Wind/SWE, we compare the He++/H+ ratios between the solar wind and the plasma sheet. We find that the plasma sheet ratio agrees well with the ratio in the solar wind, with a time delay of 0-4 hours, indicating that the solar wind is on average the dominant source. However, during active times there are strong deviations from this. The ionospheric source can reach the plasma sheet both from the dayside cusp region and from the nightside auroral region. We show the results of a recent study using Arase data that shows that the ionospheric O+ accelerated in the vicinity of the near-earth reconnection region and moving into the near-earth region along the plasma sheet boundary layer, can play a significant role in bringing hot O+ quickly to the near-earth plasma sheet during storms
Bio
Professor Kistler received her doctorate from the University of Maryland. She was a visiting scientist at the Max-Planck-Institut für extraterrestrische Physik (MPE) in Garching, Germany for two years, before coming to the University of New Hampshire, where she is now a professor in the Department of Physics and Astronomy and the director of the Space Science Center. Her main research interest is magnetospheric physics. Her particular expertise is in the analysis of ion composition data to disentangle the mix of solar wind and ionosphere sources to the magnetospheric plasma, and to understand the effects of heavy ions on magnetospheric dynamics. Her work includes the design, fabrication, and testing of state-of-the-art instrumentation for spacecraft as well as the analysis of the data collected by these instruments. She has been involved in developing instrumentation for missions that include CLUSTER, FAST, Equator-S, ACE, STEREO, Solar Orbiter, IMAP, and SOLAR. She is a fellow of the American Geophysical Union, and is an author of more than 200 papers.
If you are interested in attending, please email Lynne_Schaufenbil@uml.edu.