Particle Acceleration During Collisionless Magnetic Reconnection

This study will explore the mechanisms responsible for acceleration of high energy charged particles in solar flares and similar astrophysical events. The explosive release of magnetic energy is the driver of many important phenomena in nature, including flares on the sun and remote astrophysical objects, storms in the Earth's space environment and disruptions in laboratory fusion experiments.

Energy release in the solar atmosphere is the driver of space weather, which can negatively impact our space-based satellite communication systems and threaten the safety of astronauts in space. The release of magnetic energy takes place through a process called magnetic reconnection in which magnetic fields pointing in opposite directions annihilate.

While great progress has been made in understanding the mechanisms for the fast release of magnetic energy, the mechanisms responsible for the acceleration of charged particles to high energy remain only partially understood and are the focus of this study. In doing so, it will contribute to the goals of NSF's "Windows on the Universe: The Era of Multi-Messenger Astrophysics" Big Idea.

Solar flare observations and in situ observations in the Earth’s magnetotail suggest that a large fraction of the magnetic energy released appears in the form of energetic ions and electrons. The measured particle distributions take the form of extended powerlaws in which the number of particles at a given energy is proportional to an inverse power of that energy.

Modeling efforts of magnetic reconnection have not been successful in producing such powerlaw particle distributions. A new computational model is being developed for exploring particle acceleration in the regions of large spatial scale that characterize reconnecting systems in nature. The new model is for the first time revealing the high energy particle distributions as seen in observations and will be used to establish the underlying particle acceleration mechanisms and the partitioning of energy between electrons, protons and positively charged ions.

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.