NSF Award
2308853
This project will use spacecraft observations, numerical simulations and laboratory experiments to study how solar wind plasma -- the electrons and ions blowing off the surface of the Sun -- interact with the magnetosphere of the Earth. Space is filled with plasma consisting of approximately equal amounts of negatively charged electrons and positively charged ions. Our nearest star, the Sun, ejects large quantities of fast-moving plasma, called the solar wind, toward the Earth. This plasma is relatively cold but is rapidly heated when it encounters magnetized planets. The Earth’s magnetic field partly shields us from the solar wind, but this shield can also break via a mechanism called magnetic reconnection. It is not well understood why the plasma inside the Earth’s magnetic shield, the magnetosphere, is so hot when compared to the solar wind, and this award will enable a collaborative team from Embry-Riddle Aeronautical University and the University of Wisconsin - Madison to help address this question. The project will also contribute to our understanding of space weather and educate, mentor, and support two Ph.D students as well as three scientists from under-represented groups.<br/> <br/>The universality of particle acceleration, heating and transport in plasmas remains a major challenge in plasma physics, space physics, and astrophysics. In laboratory plasmas, the length-scales are shorter and time-scales are faster than for physical processes in space plasmas, making it a challenge to measure and identify the specific physical mechanisms responsible. In space, the in-situ measurements probe plasmas at their natural scales, but the spatial distribution of probes is very sparse. Recent multi-spacecraft observations and numerical simulations have revealed generation mechanisms of large-scale magnetic bottle structures (diamagnetic cavities) at the Earth’s dayside magnetosphere where thermal particles of tens of eV can be accelerated to suprathermal energies of greater than 40 keV. However, the detailed physics of the particle acceleration has remained elusive. This project will answer the following science questions: (1) What is the detailed physics for electron energization by reconnection (e.g., betatron vs. Fermi) in the environment of a diamagnetic cavity (DMC)?; (2) What is the time-scale of formation of the DMCs in high-Lundquist number plasmas?; (3) How do the electron plasma properties change in the DMC with respect to external electron parameters in high-Lundquist number laboratory plasmas and what controls the fraction of reconnected flux compared to flux convected around the dipole field?<br/><br/>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.
