"Understanding the Acceleration and Release of Solar Energetic Particles Using Observations from Multiple Viewpoints and in Multiple Wavelengths," presented by Dr. Bin Zhuang, a research scientist at Space Science Center of the Institute for the Study of Earth, Oceans, and Space.

Abstract:
"Understanding the Acceleration and Release of Solar Energetic Particles Using
Observations from Multiple Viewpoints and in Multiple Wavelengths"
Solar Energetic Particles (SEPs), especially for gradual and large (flux of ions with energy >10 MeV above 10 pfu) SEP events, play an important role in space weather effects as they may pose major radiation hazards for spacecraft and astronauts. Understanding the acceleration, release, and transport of SEPs in the heliosphere is one of the outstanding problems in heliospheric physics, and thus has been investigated for a long time. Since the 21st century, combining advanced observations from multiple viewpoints and in multiple wavelengths, we are able to further dig into the SEP studies.
In this presentation, we start from gradual and large SEP events which are believed to be produced by shocks associated with fast and wide Coronal Mass Ejections (CMEs). The scattering of the relationship between the SEP peak intensities and CME speeds in statistics suggests a scenario that a fast primary CME is preceded by previous CMEs is favorable to a more efficient particle acceleration (twin-CME scenario). We investigate the role of CME-CME interaction in the acceleration and release of SEPs in detail. In the twin-CME scenario, seed particle populations, which act as an important factor in the shock acceleration mechanism of energetic particles, are thought to be enhanced by preceding CMEs. We further analyze the roles of CME-CME interaction and other associated factors (e.g., magnetic connectivity, CME speed, flare size, and seed particle background) by incorporating SEP-poor events. The results show that in a statistical sense, the consideration of seed populations cannot improve the prediction of SEP peak intensities. We note that these observations for SEPs and seed populations are limited near 1 au, while particle transport effects may not be neglected. The recently launched Parker Solar Probe (PSP) and Solar Orbiter (SolO) moving close to the Sun provide unique opportunities to investigate SEPs and seed populations in the innermost heliosphere. We then study a series of SEP events between 2021 May 27 and June 1 observed by PSP and STEREO-A at different heliocentric distances, and try to answer three questions on seed particle populations: (1) how long can they exist; (2) how widely can they extend/spread; and (3) how do they measured at 1 au correspond to those in the inner heliosphere? Finally, we discuss a question/debate about the acceleration and release of SEPs in association with the coronal EUV wave (which may correspond to the footpoint of CME-driven shocks on the solar surface) based on an SEP event observed by SolO, PSP, STEREO-A, and L1 spacecraft at different locations.

About:
Bin Zhuang joined the University of New Hampshire as a postdoctoral research associate (now is Research Scientist) at the Space Science Center of the Institute for the Study of Earth, Oceans, and Space (EOS) since 2019. He has been working with Prof. Noé Lugaz since then. Bin Zhuang graduated from the University of Science and Technology of China with a PhD in Space Physics in 2019, supervised by Prof. Yuming Wang and Prof. Youqiu Hu. He is focusing on the investigation of Coronal Mass Ejections (CMEs) and Solar Energetic Particles (SEPs), by multiple remote-sensing and in-situ observations from spaceborne instruments (e.g., Parker Solar Probe, Solar Orbiter, SOHO, and STEREO), and numerical magnetohydrodynamic (MHD) simulations.