On Monday, June 2, 2025, at 12:00 c.t., the next date of our physics colloquium will take place.
Dr. Kevin Schoeffler is a postdoctoral researcher in the Computational Plasma Physics group at the Faculty of Physics and Astronomy. He also collaborates with the Collaborative Research Center 1491 at the Ruhr University and the Group of Lasers and Plasmas at the Instituto Superior Técnico in Lisbon. Schoeffler will give his lecture on "Astrophysical Magnetic Fields: Extreme Energy Source Transferred Through Plasma Interactions".
While the role of magnetic fields is often a forgotten aspect of astrophysical phenomena, magnetic fields permeate plasmas, the dominant form of visible matter throughout the universe. Near compact objects such as neutron stars and black holes, the energy density of such fields reaches the highest values on record. At these strengths, it is not uncommon that photons passing through can tap into this energy, producing copious "pair plasmas" composed of pairs of electrons and positrons. By using advanced numerical techniques to model the interactions of plasmas in these extreme magnetic fields, we have investigated the process known as magnetic reconnection [1,2,3]. Reconnection acts to release this magnetic energy in the form of relativistic
jets, particle heating, relativistic non-thermal particle acceleration, and radiation. The magnetic energy density is not as extreme in the plasma around larger-scale active galactic nuclei (AGNs). However, the total energy released from the magnetic fields is large enough to explain extremely energetic neutrino and cosmic ray observations. Magnetic reconnection is one of the most promising explanations for the acceleration of particles towards the observed energies. We further employ advanced techniques, such as semi-implicit particle-in-cell models [4], to model the extreme scale separation between the microscopic scales inherent to reconnection and the macroscopic scales of AGNs.
[1] K. M. Schoeffler et al 2023, MNRS, 523, 3 3812-3839
[2] K. M. Schoeffler et al 2019, ApJ, 870, 1
[3] K. M. Schoeffler et al 2025, JPP, 91, E42
[4] F. Bacchini 2023, ApjSS 268 (2), 60
Abstract of the presentation by Dr. Schoeffler
Prof. Dr. Hendrik Hildebrandt will give an introduction to the lecture.
The faculty cordially invites all interested parties. The event will take place in lecture hall NB 3/99.
All dates of the Physics Colloquium can be found here.
Image: Earth's magnetosphere © EvgeniyQ, Getty Images