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Events on Thursday, March 2nd, 2023

NPAC (Nuclear/Particle/Astro/Cosmo) Forum
WIPAC-astro discussion
Where are Milky Way’s Hadronic PeVatrons?
Time: 2:30 pm - 3:30 pm
Speaker: Takahiro Sudo, Ohio State University
Abstract: Observations of the Milky Way at TeV–PeV energies reveal a bright diffuse flux of hadronic cosmic rays and also bright point sources of gamma rays. If the gamma-ray sources are hadronic cosmic-ray accelerators, then they must also be neutrino sources. However, no neutrino sources have been detected. Where are they? We introduce a new population-based approach to probe Milky Way hadronic PeVatrons, demanding consistency between diffuse and point-source PeV-range data on cosmic rays, gamma rays, and neutrinos. For the PeVatrons, two extreme scenarios are allowed: (1) the hadronic cosmic-ray accelerators and the gamma-ray sources are the same objects, so that bright neutrino sources exist and improved telescopes can detect them, versus (2) the hadronic cosmic-ray accelerators and the gamma-ray sources are distinct, so that there are no detectable neutrino sources. The latter case is possible if hadronic accelerators have sufficiently thin column densities. We quantify present constraints and future prospects, showing how to reveal the nature of the hadronic PeVatrons
Host: Lu Lu
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Plasma Physics (Physics/ECE/NE 922) Seminar
Life Cycle of Magnetized Plasmas in the Universe
Time: 2:30 pm
Place: B343 Sterling Hall
Speaker: Young Dae Yoon, Asia Pacific Center for Theoretical Physics
Abstract: Magnetized plasmas are ubiquitous in the Universe and are important because many of the events therein are governed by their dynamics. Understanding their nature is thus crucial in various contexts including nuclear fusion, space, and astrophysics. Magnetized plasmas typically undergo three cyclic processes: “generation” of magnetic fields by the plasma, “relaxation” of the system to an equilibrium, and “explosion” of the stored magnetic energy back into the plasma. In this talk, I will present recent results in selected sub-processes within these categories, namely magnetic reconnection, ion energization, wave-particle interaction, and current sheet relaxation. I will then briefly discuss my vision for future work that calls for continued and expanded investigations of these processes.
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