Supervisor : Prof Steve Milan (ets@ion.le.ac.uk)

Details of Project

The interaction of the solar wind with the Earth’s magnetosphere is mediated through a process known as magnetic reconnection occurring at the magnetopause.  As magnetic reconnection occurs, the magnetosphere becomes interlinked with the interplanetary magnetic field, that is, ever more “open” allowing the ingress of solar wind plasma, causing the aurorae to brighten and move to lower latitudes, and swelling the magnetotail of the planet.  This situation cannot be supported indefinitely and magnetic reconnection is induced within the magnetotail to disconnect the planet from the solar wind once again, resulting in vivid auroral displays on the nightside of the planet, known as the auroral substorm.  Hence, the substorm is the quantum of plasma, magnetic flux, and energy transport in the magnetosphere, and as such it is central to the whole of magnetospheric dynamics.

A sequence of global auroral images from November 2001, captured by the NASA IMAGE spacecraft, showing the development of the auroral oval during a geomagnetic storm and multiple substorms, whose progress is monitored by the DST index, a measure of ring current activity.

Although the substorm process has been studied for 40 years, recently rapid advances in our understanding have resulted from the availability of new datasets and new paradigms for comprehending the coupling within the solar wind-magnetosphere-ionosphere system that causes substorms and feedback mechanisms within the magnetosphere that modulate the coupling.  The RSPP group has been at the forefront of this recent research, and continued research could form the basis of one or more PhD projects.  For instance: what triggers the onset of tail reconnection?; what is the role of geomagnetic storms in governing substorm behaviour?; why does the magnetosphere sometimes respond differently to solar wind coupling, displaying “steady magnetospheric convection” or “sawtooth” events?  These projects will involve a combination of data analysis and theoretical work. 

Sources of Data

The Earth has the best-observed planetary magnetosphere in the solar system.  Data from many sources will be used in this project, including the ESA Cluster and NASA THEMIS satellite missions, the NASA Polar and IMAGE auroral imaging spacecraft, the SuperDARN ionospheric radars, and suites of other space- and ground-based observatories. 

Background Reading

Examples of recent research papers in this area from the RSPP group, produced by and with students:

Milan et al., 2003: Ann. Geophysicae, 21, 1121-1140.

Imber et al., 2006: Ann. Geophysicae, 24, 3115-3129.

Milan et al., 2008: J. Geophys. Res., 113, A09215, doi: 10.1029/2008JA013340.

Boakes et al., 2009: Geophys. Res. Lett., 36, L04105, doi: 10.1029/2008GL037059.

Milan et al., 2009: Ann. Geophysicae, 27, 659-668.

Milan et al., 2010: J. Geophys. Res., 115, A00104, doi: 10.1029/2010JA015663.