Solar Physics

This is my main area of work currently, joining a very active group in Solar Physics. As well as here I shall be updating my University web pages as work proceeds. My Principle Investigator and new mentor is Prof. Robert von Fay-Siebenburgen.

Project

Numerically model magnetic flux tube behaviour in the solar atmosphere. We investigate the mechanism by which the coronal temperature increases from around 4x10³ Kelvin at the visible surface of the sun to over a 10⁶ Kelvin, within a few million metres. Note the visible surface (photosphere) is at a solar radius of about 696 Mm.

With the huge differentials in plasma density (9 orders of magnitude) and pressure (6 orders) modelling the lower solar atmosphere is numerically challenging. We take advantage of the relatively steady state of the magnetic flux tubes and loops extending through this region into the corona, to model the smaller differentials of the fluctuations of the magnetic field and atmosphere.

A single magnetic flux tube - field lines plotted in blue. The atmosphere is in equilibrium. The isosurfaces represent plasma-beta. To construct the steady magnetized background atmosphere we have been solving analytically the time-independent MHD equation of momentum conservation. This has been completed for a single flux tube and also for systems of multiple flux tubes. The first Figure displays a 3D image of the single flux tube, identified by the magnetic field lines in blue. Plasma-beta is the ratio of thermal to magnetic pressure and the isosurfaces in the Figure are obtained from our solution for the background atmosphere, with such a magnetic field configuration.

Image of two pairs of flux tubes of the form used in the single flux tube. These are combined to form a non-axisymmetric, non-uniform magnetic field. The atmosphere is in equilibrium, with appropriate balancing forces calculated and applied.

The video below left is an early 360^o view of a multiple flux tube configuration, obtained by adding a number of single flux tube configurations together, but without fully solving the atmospheric equilibrium state. The video below right shows a 360^o view of a more challenging configuration, for which the equilibrium atmosphere has been solved in full. Balancing forces are required to complete this equilibrium, which we have also calculated in full.

Further results and work to follow.