School of Physical and chemical Sciences Te Kura Matū Seminar Series

Particle acceleration at supernova remnants

Speaker

Martin Pohl

Institute

Deutsches Elekronen-Synchrotron DESY, Institute of Physics and Astronomy, University of Potsdam

Time & Place

Wed, 04 Mar 2020 12:00:37 NZDT in Room 112, Beatrice Tinsley Building

All are welcome

Abstract

The universe is filled with a sea of energetic charged particles whose kinetic energy can reach that of a well-played tennis ball. How and where these particles are produced is a major question in modern astrophysics. Supernova remnants are ideal objects to study particle acceleration in space because they are persistent and bright emitters of nonthermal radiation and they can be observationally resolved. It has been known for a long time that kinetic coupling of charged particles to plasma waves can lead to particle acceleration, if as in supernova remnants fast outflow interact with a slow ambient medium. It is also known that earlier steady-state notions of nonlinear feedback by the accelerated particles fail, as they predict particle spectra that are much harder than is observed. Recent modelling indicates that the processes that govern the acceleration and the transport of energetic particles are very nonlinear at all levels, and accounting for the full time dependence of the nonlinearity, one finds particle spectra and spatial distributions as observed.

Biography

Martin Pohl is Leading Scientist at DESY and works in the field of astroparticle physics and Professor for theoretical physics at Potsdam University. He and his team study energetic particles in the universe, their sources, their interactions with their environment, and their decay products. The universe harbors systems that are capable of accelerating individual particles to energies many orders of magnitude higher than is possible with accelerators built by humans. What drives these systems is a major question in physics and understanding them has broad implications. Scientific questions include: How do cosmic sources accelerate particles to very high energies? How do supermassive black holes for form jets and energetic particles therein? What is the nature of dark matter in the universe?