[English]

Hydrodynamic properties of the solar wind

(supervisor: Youra Taroyan)

Nature of project: theory, theory

Available to full-time physicists or joint students.

Project description and methodology

The idea of solar wind was proposed in the early 20th century by Kristian Birkeland who believed that the charged particles were being continuously ejected from the Sun. The first theories for solar wind emerged in the 1950s. Several key questions concerning the hydrodynamic properties of the solar wind will be addressed. In particular the project will explain why the atmosphere of the Sun cannot be in a hydrostatic equilibrium. Further, the speed of the solar wind will be estimated in the low corona and compared wth the sound speed. The mass loss rate of the Sun due to the wind will be estimated. Finally, the question of a maximum temperature for an isothermal wind will be addressed.

A successful project will develop beyond the above in one/some of the following directions:
The properties of a polytropic solar wind will be investigated. The location of the point where the wind becomes supersonic from subsonic will be determined. The implications of vanishing pressure with distance will be studied.

When considering where to take your project, please bear in mind the time available. It is preferable to do fewer things well than to try many and not get conclusive results on any of them. However, sometimes it is useful to have a couple of strands of investigation in parallel to work on in case delays occur.

Additional scope or challenge if taken as a Year-4 project: The question of minimum/maximum temperatures for the existence of a polytropic/adiabatic wind will be addressed.

Initial literature for students:

  1. E. Priest, Magnetohydrodynamics of the Sun
  2. M. Aschwanden, Physics of the solar corona
  3. M. Stix, The Sun

Novelty, degree of difficulty and amount of assistance required

The project does not require data analysis or use of software. It is suitable for those interested in analytical work.

Project milestones and deliverables (including timescale)

milestoneto be completed by
Understanding of the equations governing the solar windend of October
Review and summary of the main conceptsChristmas
Derivation of the main resultsmid-March