96394 - Magnetic Fields in Astrophysics

Academic Year 2022/2023

  • Teaching Mode: Traditional lectures
  • Campus: Bologna
  • Corso: Second cycle degree programme (LM) in Astrophysics and Cosmology (cod. 5828)

Learning outcomes

During the course, the student will learn the basics of magnetised plasma in astrophysics. The origin of magnetic fields in the primordial Universe as well as the magnetic field properties of astrophysical objects will be discussed. The student will also learn the main techniques to derive magnetic field properties in astrophysical objects from observations. During the laboratory, these techniques will be used by the student using real data.

Course contents

- Magnetohydrodynamics: basic equations, induction equations, resistive MHD, magnetic flux freezing, dissipation processes, Magnetic Prandtl number, magnetic Reynold number, the beta parameter, ambipolar drift, two-fluid approximation, magnetic helicity, MHD waves.

- Origin and amplification of Magnetic field: generation of magnetic seed fields, Biermann Battery,  amplification due to gravitational collpase, MHD dynamos. Large-scale dynamo and time evolution of the magnetic field

- Observational methods to constrain magnetic fields in astrophysics: Zeeman effect, polarisation, Faraday effect, The Rotation measure synthesys, Q-U fitting technique

-Magnetic field in galaxies: observational properties, magnetic energy density, cosmic ray propagation, relation between gas, start formation, and magnetic fields.

-Magnetic field in clusters of galaxies: observational properties, the magnetic field power spectrum, radio emission in clusters of galaxies: radio halos, relics, and mini halos, effect on thermal conduction.

-Magnetic fields on large-scales: intracluster bridges and magnetic fields in the cosmic web

- In the laboratory, magnetic field properties of  astrophysical objects will be derived using real data and the technique explained in the course.

 

Readings/Bibliography

A. Brandenburg and K. Subramanian, "Astrophysicl magnetic fields
and nonlinear dynamo theory", Physics Reports, volume 417, pages 1-209 (2005)

Ruzmaikin, A.A., Sokoloff, D.D., Shukurov, A.M. "Magnetic Fields of Galaxies" Astrophysics and Space Science Library, Springer Netherlands

Scientific papers will be specified during the lectures

 

 

 

Teaching methods

Lecture at the blackboard and using slides

Assessment methods

Presentation of the lab project, oral exam

Office hours

See the website of Annalisa Bonafede