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Unit information: The Physics of Gas and Plasma in the Universe in 2020/21

Unit name The Physics of Gas and Plasma in the Universe
Unit code PHYSM3409
Credit points 10
Level of study M/7
Teaching block(s) Teaching Block 1 (weeks 1 - 12)
Unit director Dr. Young
Open unit status Not open

Second year Classical Physics units.



School/department School of Physics
Faculty Faculty of Science


The vast majority of the baryonic Universe is in the form of gas and plasma existing in a diverse range of conditions. This course uses these astrophysical contexts as a backdrop against which to examine a broad range of physical processes that are important to understanding the behaviour of gases and plasmas. We will review important gas and plasma concepts, and then consider topics including: the Solar Wind and its impact on the Earth; accretion disks around compact objects; the interstellar medium in the Galaxy including excitation, ionisation and energy transport mechanisms, with applications to neutral hydrogen, HII regions, supernova remnants and ionization fronts; galactic winds and their effect on galaxy evolution; the plasma atmospheres of clusters of galaxies, including their heating and cooling mechanisms, the feedback between the member galaxies and this plasma, the production of radio halos.


To describe and explain the varied processes which are key to gas phase astrophysics and plasma astrophysics. These processes include collisions, ionisation, sound waves, shocks, and viscosity. To develop and use a mathematical description of these processes, including the equations of compressible fluid flow, Bernoulli’s theorem, Rankine-Hugoniot shock jump conditions, spherical inflows and outflows, viscous flows, ionisation fronts, supersonic expansion, and radiative cooling of gas. To apply these mathematical techniques to solve a range of physical problems in different contexts, including supersonic flows, the Solar wind, accretion disks, H II regions, supernova remnants and galaxy clusters. To provide an appreciation of the ubiquitous presence of gases and plasmas throughout the Universe, from the near-Earth environment, to the diffuse intergalactic medium in clusters of galaxies, as well as their importance for energetic processes in the Universe.

Intended learning outcomes

Students should be able to describe the main processes which control the gas phase and plasma content of the universe, on a range of scales from the near-Earth influences of the Solar Wind, to the production of radio halos in the intracluster plasma in clusters of galaxies. They should be able to discuss the different phases of the interstellar medium of our own and other galaxies, and be able to make calculations on the behaviour and development of, for instance, ionization fronts and galactic winds.

Teaching details

The unit will be taught through a combination of

  • asynchronous online materials, including narrated presentations and worked examples
  • synchronous group problems classes, workshops, tutorials and/or office hours
  • asynchronous directed individual formative exercises and other exercises
  • guided, structured reading

Assessment Details

Formative feedback is provided through problems classes.

Written timed, open-book examination (100%)

Reading and References

  • Clarke and Carswell, Principles of Astrophysical Fluid Dynamics (CUP)
  • Spitzer, Physical Processes in the Interstellar Medium (Wiley)
  • Choudhury, The Physics of Fluids and Plasmas (CUP)
  • Longair, Galaxy Formation (Springer)