PhD Position at Northumbria University, UK

Differentially rotating flows, i.e. the flows in which the fluid parcels move with a velocity that depends on the distance from the axis of rotation, widely occur both in natural and industrial environments. Gas flow orbiting a gravitating centre, like a star, tends to acquire a form of a flat disk that rotates differentially according to the laws of Kepler. The Keplerian rotating flow should be laminar according to the centrifugal Rayleigh criterion because the angular momentum of the Keplerian flow decreases with the increase in the distance from the star. Nevertheless, observations show that the matter in the accretion disks is in the turbulent state. The apparent paradox can be resolved if one takes into account that the matter of the disk is usually ionized and thus electrically conducting and that the stars usually have magnetic fields. Even weak magnetic fields turn out to be capable to destabilize a Keplerian disk if the fluid is a good electrical conductor. When the conductance is poor, the destabilizing properties depend on the spatial distribution of the magnetic field. Recently, it has been shown theoretically in the short-wavelength WKB approximation that helical and azimuthal magnetic fields are capable to induce the magnetorotational instability even in poorly electrically conducting Keplerian flows. The aim of the PhD project is to prove this property by solving a boundary value problem with a variety of boundary conditions. The non-self-adjoint boundary value problem will require a perturbative, asymptotic and numerical treatment and will involve such concepts as negative energy waves, dissipation-induced instabilities, and Hamiltonian mechanics. As a first step, a magnetized Couette-Taylor flow with the quasi-Keplerian shear profile is planned to consider with the subsequent transition to more realistic models of accretion disks. The theory is mathematically challenging but highly demanded by both astrophysical and magnetohydrodynamics communities.

Eligibility and How to Apply

Please note eligibility requirement:
• Academic excellence of the proposed student i.e. 2:1 (or equivalent GPA from non-UK universities [preference for 1st class honours]); or a Masters (preference for Merit or above); or APEL evidence of substantial practitioner achievement.
• Appropriate IELTS score, if required (evidence required by 1 August 2017).

For further details of how to apply, entry requirements and the application form, see
https://www.northumbria.ac.uk/research/postgraduate-research-degrees/how-to-apply/

Please ensure you quote the advert reference above on your application form.
Deadline for applications: 20 January 2017
Start Date: 2 October 2017

Northumbria University is an equal opportunities provider and in welcoming applications for studentships from all sectors of the community we strongly encourage applications from women and under-represented groups.