Neutron stars have the strongest magnetic fields in the Universe. These fields are formed as a result of dynamo action during a short proto-neutron star stage. We use the DIaL3 to model evolution of magnetic field configurations produced as a result of accretion on the proto-neutron star. We noticed that these magnetic field configurations are in the form small scale-structure as shown in the image. These small-scale structure can lead to formation of absorption lines in X-ray observations. (Work undertaken by Andrei Igoshev and Rainer Hollerbach.

Gravitational tidal interactions play important roles in extrasolar planetary systems and in binary star systems. For example, dissipation of tidal flows excited in giant planets by their stars (much like the tidal flows excited in Earth’s oceans by the Moon and Sun) is thought to cause orbital evolution of planetary eccentricities, perhaps explaining why hot Jupiters with orbital periods shorter than 10 days are primarily circular. We use DIal3 to model the excitation and dissipation of tidal waves in the convective envelopes of giant planets with short orbital periods around their stars, for which nonlinear fluid effects are important. Our recent results, published in The Astrophysical Journal Letters, show that nonlinear fluid effects can substantially modify astrophysical predictions for tidal dissipation rates over previous linear calculations in these systems, primarily due to the generation of differential ro- tation in the form of zonal flows inside these planets that affects the propagation and dissipation of tidal inertial waves (restored by Coriolis forces). This means that exoplanet systems could evolve very differently to previous linear predictions. This figure shows tidal dissipation rates as a function of tidal frequency (normalised to the planet’s rotation rate) for a thin convective envelope (with a “solar- like” 70% thickness, here a giant planet with an extended core) and realistic tidal forcing for the closest hot Jupiter systems (dimensionless tidal amplitude of order 0.05). The colours represent energy in the differential rotation and the solid black line is the prediction of linear theory (i.e. assuming the tidal amplitude to be very small).

For more details, see: Astoul & Barker, The Astrophysical Journal Letters 955 (1), L23. (Work under- taken by Aurélie Astoul and Adrian Barker.)

Astrophysical Fluid Dynamics at Leeds (dp216 using DIaL3)

PI: Prof Adrian Barker (on behalf of the team) University of Leeds