96394 - Magnetic Fields in Astrophysics

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.

The laboratory consists of three different exercises. Each of them will be explained and done together, guiding the students step by step. Then, a similar problem will be assigned, that the students will repeat by themselves.

 

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

During the lecture, the professor will use both the tablet and slides.

The pdf transcript of the tablet will be published on Virtuale after each class, while the slides will be available before the class.

Assessment methods

Two working days before the exam, the student must submit a written report of approximately 3–4 pages describing one of the laboratory experiments.

The exam is oral, lasts about 30–40 minutes, and consists of:

1. A presentation and discussion of the laboratory experiment chosen by the student.

2. Two or three questions on topics covered during the lectures.

The oral exam is graded on a 30-point scale and is considered passed with a minimum score of 18/30.

The oral exam grade is determined based on the following criteria:

• 18–21: Limited preparation covering only a subset of topics, with critical thinking skills emerging only with help from the examiner.

• 22–25: Good preparation across a broad range of topics, but critical thinking is only partially autonomous.

• 26–29: Good preparation on all topics covered in the course, along with solid independence and critical thinking.

• 30: Comprehensive preparation, excellent independence, and strong critical thinking.

• 30 with honors (30 e Lode): Exceptional preparation and the ability to connect various topics discussed in class, reaching new insights, with the help of the professor, that were not explicitly covered during lectures. 

The grade can be refused up to two times, in accordance with the rules established by the Degree Program Committee (CdS).

Students with learning disabilities or temporary or permanent disabilities: please contact the relevant University office promptly (https://site.unibo.it/studenti-con-disabilita-e-dsa/it ). The office will advise students of possible adjustments, that will be submitted to the professor for approval 15 days in advance. He/she will evaluate their suitability also in relation to the academic objectives of the course.

 

 

Teaching tools

slides, tablet.

Office hours

See the website of Annalisa Bonafede