Speakers and Topics
Speakers and Topics
Below we describe for each lecture a short outline. The lecturers are all confirmed, unless specified.
- Acceleration on all scales (introduction to the school): Felix Aharonian (DE,IE)
The intention of this talk will be the discussion of high-energy non-thermal phenomena on all scales, which will include a general discuss of particle acceleration in different astrophysical environments. The discussion will have a phenomenological character without details on acceleration mechanisms, which will be covered in other talks. On the other hand, it will be discuss the non-thermal phenomena in general, and particle acceleration in particular in the context of relativistic outflows, including jets of different scales.
Prof. Aharonian will not be able to be present at the School. His lectures will be given by the School Director Dr. D. Götz
- Radiative Processes I (non thermal): Alexandre Marcowith (FR)
Non-thermal radiations are ubiquitous in sites of acceleration of energetic particles to high energies. The lecture will provide a rather exhaustive review of these processes and illustrate them with some particular relevant astrophysical cases. Both compact objects and diffuse environments will be discussed.
- AGNs: Volker Beckmann (FR)
Active Galactic Nuclei provide particle accelerators that produce confined jets up to distances of 100 kpc and more. This lecture will discuss the current status of AGN research, with a special emphasis on AGN displaying jets. What types of AGN can become strong particle accelerators? How does the AGN interact with its environment and how did the AGN population evolve on cosmological time scales? The lecture will then focus on the emission processes we observe in blazar jets. Here we can study the physical processes, such as synchrotron self-Compton and external Compton processes. In radio galaxies we can directly observe spatial components, or "blobs", as they are being emitted and then as they travel downstream. Shocks and knots in the jet have been identified and sensitive observations in other wavebands allow us to correlate morphological evolution in the radio to the multi-wavelength light curves. But the main question still persists: how are the jets formed in the first place? This question is tightly connected to the accretion process powering the AGN and the central (Kerr?) black hole.
- Radiative processes II (thermal): Jelle Kaastra (NL)
The lecturer will present the basics of high-resolution X-ray spectroscopy. After a brief summary of atomic structure, the basic processes related to emission and absorption in a plasma are introduced. Examples that are encountered frequently are presented but also some challenging diagnostics that will become available with future instruments are described.
- SNRs: Jacco Vink (NL)
For a long time supernova remnants have been thought to be the main contributors to the observed cosmic-ray flux below 3x1015 eV. Since 20 years the amount of evidence that this is indeed the case has rapidly increased. Recent gamma-ray and X-ray observations inform us that particles are accelerated at least up to 100 TeV, and there is evidence that a significant amount of kinetic energy is converted to cosmic-ray energy. Nevertheless, the final evidence of particles with energies approaching 3x1015 eV is still lacking, and also the evidence that more than 10% of the SNR energy is in cosmic rays is still not secure. The lecturer will discuss the observational situation and what remains to be done in the future.
- Acceleration Processes I (Fermi I): Andrei Bykov (RU)
Particle acceleration by collisionless shocks waves (Fermi I type acceleration) is proved to be the most efficient mechanism of relativistic particle production in many astrophysical objects with high-energy release - supernova remnants, stellar winds, jets etc. The high efficiency of particle acceleration implies the importance of non-linear feedback effects connecting self-generated fluctuating magnetic fields and non-thermal particles. These lectures will review the current status and perspective of the Fermi I mechanism in connections with high-energy astrophysics.
- Acceleration Processes II (Fermi II and Monte Carlo): Don Ellison (USA)
There is substantial evidence that magnetic fields can be strongly amplified in some astrophysical sources. The stronger the magnetic field, the more important second-order Fermi particle acceleration becomes as particles scatter off the strong magnetic turbulence. The lecturers will discuss how the predictions of second-order Fermi acceleration differ from those of the more widely used first-order Fermi mechanism and emphasize the application to cosmic-ray production in young supernova remnants.
- Acceleration Processes III (Magnetic reconnection, Charge separation, Poynting Fluxes, rotating B Fields, Jets): Henk Spruit (DE)
Introduction to magneto-hydrodynamics (MHD) with emphasis on processes of flow acceleration by magnetic fields, the interpretations of the Poynting flux in MHD. As a practical application of MHD this will be followed by the rotating magnetic field model for the acceleration of astrophysical jets, including Poynting flux conversion into kinetic energy, the collimation of jets, and finally the role of internal instabilities of the magnetic field in jets in the dissipation of magnetic energy, and their contribution to flow acceleration.
- PWNe: Elena Amato (IT)
These lectures will provide a review of the current status of our knowledge on Pulsar Wind Nebulae. The lecturer will mostly be concerned with their role as cosmic ray factories. They are natural sources of leptonic anti-matter and also the only class of astrophysical objects for which we have direct evidence of particle acceleration up to PeV energies. The lecturer will summarize what we understand of the processes through which the rotational energy of the central pulsar is first converted into a highly relativistic magnetized wind and then into acceleration of particles up to the highest energies achieved in the Galaxies.
- GRBs: Frederic Daigne (FR)
Gamma-ray bursts are bright transient phenomena associated to ultra-relativistic outflows ejected by newborn compact sources. The lecturer will review the main observations and our current physical understanding of these phenomena. Then the lecturer will discuss particle acceleration in GRBs: (i) acceleration of the particles responsible of the observed gamma-ray emission; (ii) acceleration of hadrons and possible signatures in gamma rays or neutrinos; (iii) possible acceleration of ultra-high energy cosmic rays.
- Simulations: Lorenzo Sironi (USA)
The lecturer will discuss recent progress in our understanding of collisionless astrophysical shocks, thanks to powerful ab initio plasma simulations. Fully kinetic particle-in-cell (PIC) simulations simultaneously capture the kinetic physics of electrons, whose emission powers the radiative signature from astrophysical sources, and of protons, that regulate the shock dynamics and evolution. In hybrid simulations, where only protons are treated kinetically (here, electrons constitute a massless charge-neutralizing fluid), the shock evolution can be followed up to much longer times than in PIC simulations, thus approaching the time and length scales most relevant to astrophysics. Thanks to recent advances in numerical algorithms and computer capabilities, PIC and hybrid simulations have allowed major progress in our understanding of the physics of shock formation, magnetic field generation, and particle acceleration, thus contributing to unveil the nature of the most powerful astrophysical sources.
- Cosmic Rays I (galactic): Vladimir Ptuskin (RU)
The lecturer will discuss the processes of cosmic-ray acceleration and propagation in the Galaxy. Discussion includes the acceleration in supernova shocks, the nature of “knee” in cosmic ray spectrum at energy 3 PeV, the transition from galactic to extragalactic component, the collective effects of cosmic rays in the Galaxy.
- Cosmic Rays II (extragalactic): Martin Lemoine (FR)
The origin of cosmic rays with energy E> 1018 eV represents a long-standing problem in astrophysics, even though the development of gigantic detectors has brought in key experimental results. This course will discuss offer an introduction to the physics and the astrophysics of ultra-high energy cosmic rays. It will first discuss the recent experimental results, then it will discuss the physics of acceleration in powerful astrophysical sources and the physics of transport in the intergalactic medium; finally it will discuss the significance of recent experimental results and the prospects for future detectors.
- Isolated Neutron Stars: Andrea De Luca (IT)
Isolated Neutron Stars (INS) are supposed to host the most extreme physical conditions existing in the local universe. 45 years of multi-wavelength astronomy unveiled a complex and rich phenomenology, which led to a classification into different "species". First, the lecturer will review and discuss such "INS diversity", pointing to actual genetic/evolutionary differences, possibly related to the INS' gigantic, rotating magnetic fields. Then, the lecturer will focus on INS as strong emitters of non-thermal electromagnetic radiation, originating from charged particles accelerated in their magnetospheres, at the expense either of their rotational energy reservoir, or of the decay of an ultra-high magnetic field.
- HE Binaries: Guillaume Dubus (FR)
Observations of high-energy gamma-ray emission offer new insights into non-thermal processes in binaries. The lecturer will explain what the observed variability and orbital modulations tell us about the origin of the high-energy particles. In addition the lecturer will present the challenges that models currently face and discuss the consequences on our understanding of pulsar winds, relativistic jets and colliding stellar winds.