Magnetic Reconnection in High Definition

The region of space around the Earth is highly dynamic, driven by a fundamental physical process called magnetic reconnection. Reconnection occurs in hot gases called plasmas. When two plasmas come into contact, the magnetic fields in the two regions can become interconnected, causing the release of large amounts of energy. Reconnection occurs throughout the Universe; it is responsible for solar activity, it occurs in various astrophysical bodies and in laboratory plasmas (such as the fuel in experimental fusion reactors). However, the range and quality of instrumentation available to observe reconnection in Earth's environment makes this the best place to study this process; this is also the environment in which reconnection has the most impact on our day-to-day life, as the dynamics that are driven by reconnection have negative effects on modern day technology (space weather). For example, geomagnetic storms are driven by reconnection and cause damage to infrastructure on the ground; they also cause variations in intensity of the radiation belts which can harm satellites. Earth's auroras are also ultimately driven by the reconnection process.

Reconnection at Earth occurs at the interface between two plasmas: the solar wind, which flows from the Sun to the outer reaches of the Solar System, and the magnetosphere, which is a cavity in the solar wind that is carved out by the Earth's magnetic field. These two plasmas have associated magnetic fields: the interplanetary magnetic field (IMF) and terrestrial magnetic field respectively. Reconnection can occur between the IMF and the terrestrial field at the interface between the magnetosphere and solar wind, which is called the magnetopause - it is reconnection at this interface that transfers energy and momentum from the solar wind into the magnetosphere and provides the ultimate driver for all magnetospheric dynamics. Here, reconnection occurs both in steady state and in bursts called flux transfer events (FTEs). Reconnection similarly controls the dynamics, to greater or lesser degrees, of most magnetised planets in the Solar System, and hence it is likely to be a significant process at most magnetised exoplanets too.

In October 2014, NASA will launch a constellation of four spacecraft called the Magnetospheric Multiscale (MMS) mission, which will provide observations of the plasma environment in the Earth's magnetosphere at temporal resolutions that are far greater than previous missions. Most of the research effort in the MMS community is likely to be directed towards understanding the microphysics of reconnection, whilst the work outlined in the fellowship programme associated with this proposal will be resolving outstanding issues relating to the global scale contribution of bursty reconnection (FTEs) using data from previous missions. Here, we propose the use of the instrumentation provided by MMS to obtain a much greater understanding of FTEs on the mesoscale, which separates these two extremes (micro- and global scales). Hence it will complement both the study of the global-scale effects that is outlined in the fellowship programme and the research currently planned by the MMS team.

The objective of this proposal is to test competing mechanisms for the manner in which bursty reconnection occurs at the Earth's magnetopause. This is necessary for the verification of global simulations of magnetospheric dynamics, but it will also inform our understanding of the underlying nature of reconnection, which is often time-varying (for reasons that are unclear). This will be done by applying a range of techniques that have individually been tested, but not combined; their separate application has led to a patchy picture with results that at times appear to conflict. By applying these methods together to a common data set derived from novel high resolution instrumentation, we will gain a deeper understanding of the manner in which this fundamental physical process occurs.

The research proposed here has impact in four main areas: outreach, interdisciplinary research, societal impact and researcher development.

One of the most visible manifestations of the magnetospheric dynamics driven by the process being studied in this proposal is the Earth's aurora. Members of the public have an almost universal fascination with the northern and southern lights, and this provides an excellent opportunity for outreach activities, as people of all ages are keen to hear about the science behind the aurora (and hence magnetospheric physics in general) regardless of their level of expertise in physics.

The research carried out in the field of magnetospheric physics is now finding a broader audience through researchers in other disciplines, most notably astrophysics. This is occurring on two fronts. First, modelling of exoplanetary magnetospheres is a topic of active current interest; this research directly benefits from equivalent research within the Solar System, as the magnetospheric systems surrounding our own star are far better observed and therefore much better constrained. Second, the study of magnetic fields of other bodies in our galaxy and beyond is another actively developing topic, as evidenced by the establishment of the LOFAR Key Science Project on Cosmic Magnetism. (LOFAR is the Low Frequency Array - a large radio telescope system.) Both of these are areas in which we hope to make interdisciplinary links in the future.

The field of space weather research depends on a thorough understanding of the physics behind magnetospheric dynamics, which will be investigated in this project. Some of the most significant effects on our ground- and space-based technological infrastructure are due to geomagnetic storms, which are periods of enhanced driving by the reconnection process studied in this project. As we become more dependent on sensitive technological infrastructure, we will rely more on accurate modelling of the magnetospheric environment. The enhanced understanding of magnetospheric dynamics that will be provided by this project will contribute to this effort.

If funded, this proposal will employ a PDRA. The training and career development of that researcher will be an integral part of the project, such that whatever the PDRA's long term employment (whether it be in academia, the private sector or elsewhere), the scientific skills developed through this research programme will make an important contribution to that organisation and the wider economy.