University of St Andrews

Key information

SCOTCAT credits : 15

ECTS credits : 7

Level : SCQF level 11

Semester: 1

Availability restrictions: This module is intended for students in the final year of an MPhys or MSci programme involving the School, and for those on the Astrophysics MSc

This module is aimed at both physics and astrophysics students with interests in the physics of plasmas. The interaction of a magnetic field with an ionized gas (or plasma) is fundamental to many problems in astrophysics, solar- terrestrial physics and efforts to harness fusion power using tokamaks. The syllabus comprises: Solar-like magnetic activity on other stars. The basic equations of magneto-hydrodynamics. Stellar coronae: X-ray properties and energetics of coronal loops. Energetics of magnetic field configurations. MHD waves and propagation of information. Solar and stellar dynamos: mean field models. Star formation: properties of magnetic cloud cores, magnetic support. Physics of accretion discs: transport of mass and angular momentum. Accretion on to compact objects and protostars. Rotation and magnetic fields in protostellar discs. Rotation distributions of young solar-type stars. Magnetic braking via a hot, magnetically channelled stellar wind.

Relationship to other modules

Pre-requisite(s): null

Learning and teaching methods and delivery

Weekly contact: 3 lectures or tutorials

Scheduled learning hours: 30

Guided independent study hours: 120

Assessment pattern

As used by St Andrews: 2-hour Written Examination = 100%

As defined by QAA
Written examinations : 100%
Practical examinations : 0%
Coursework: 0%

Re-assessment: Oral Re-assessment, capped at grade 7

Personnel

Module coordinator: Professor M M Jardine

Additional information from school

AS5002 - Magnetofluids and Space Plasmas

Overview

The interaction of a magnetic field with an ionised gas (or plasma) is fundamental to many problems in astrophysics. Star formation in particular is heavily influenced by the magnetic fields of molecular clouds, and once stars form they can, if they posses a convective region, generate their own magnetic fields by dynamo activity. The behaviour of this magnetic field is at the heart of many of the most interesting observations of young stars and their accretion disks.

This module is suitable for physics students as well as astronomers. PH4031 Fluids or MT4509 Fluid Dynamics are recommended as prior study.

Aims & Objectives

To present an account of the theory and observations of magnetic activity in solar-like stars, including an introduction to magnetohydrodynamics, the physics of heating stellar coronae to temperatures of 10^{^}6K, the generation of stellar magnetic fields by dynamo action, the role of magnetic fields in star formation, the physics of accretion disks, stellar spin down by accretion disks and stellar winds.

Learning Outcomes

By the end of the module students should have an understanding of the physics of stellar magnetic fields as presented in the lectures and should be able to

• Describe the main observational signatures of magnetic activity
• Use the magnetohydrodynamic equations describe the behaviour of simple magnetic field configurations
• Give an account of the heating of stellar coronae and derive the scaling relations for pressure, temperature and length of magnetic loops
• Describe the main observational features of solar and stellar dynamos and calculate the characteristics of a simple kinematic solution
• Use the Virial theorem to explain the characteristics of magnetic support of molecular clouds and the onset of cloud collapse
• Demonstrate the role of viscosity in accretion disks and determine the temperature profile of such a disk
• Use torque balance in an accretion disk to explain stellar spin-down by star-disk coupling
• Use conservation of mass and momentum to derive Parker's wind solution and describe the role of magnetic channelling in a rotating star
• Determine the angular momentum loss rate for simple examples

Synopsis

Review of observations of stellar magnetic activity. Equations of magnetohydrodynamics (MHD) Heating of stellar coronae. Reconnection. Energetics of coronal loops and the role of rotation MHD waves and propagation of information. Solar and stellar dynamos (mean field models). Star formation: properties of magnetic cloud cores, magnetic support and the Virial theorem. Accretion disks: transport of mass and angular momentum, role of viscosity. Temperature profiles. Stellar spin down by magnetic star-disk coupling. Rotation distributions of young solar-type stars. Magnetic braking by stellar winds.

Recommended Books

Please view University online record:

http://resourcelists.st-andrews.ac.uk/modules/as5002.html

General Information

Please also read the general information in the School's honours handbook that is available via https://www.st-andrews.ac.uk/physics-astronomy/students/ug/timetables-handbooks/.