Determining and understanding substorm energy loss and partitioning

The substorm is a repeatable earthquake-like disturbance to near-Earth Space, which, apparently unpredictably, recurs after anything from 2 hours to a day or more and dumps typically one thousand million million Joules of energy into the upper atmosphere equivalent to ten Oklahoma tornados or the largest nuclear weapon in the US arsenal. The substorm's intermittency and variable size makes it arguably the greatest source of uncertainty in predicting the state of the upper atmosphere. Its most obvious effect is the aurora, which would be nice to know when its happening so that we could plan our Arctic holidays, but substorm prediction is also important for mitigating the effects of natural changes in the upper atmosphere on geostationary satellite communications and navigation, low-altitude satellite orbits and remote sensing, electricity power grids, and oil and mineral prospecting. Prediction is also the ultimate test for our scientific understanding. Progress requires measuring and analysing substorm variability in order to test and develop models based on maths and physics. We already know the statistics of substorm timing and have explained this with a simple mathematical model (that has also been used for understanding neuron firing in the brain!). However, knowing and understanding the variability of substorm size is much harder because it requires to measure simultaneously over large regions of the polar upper atmosphere and out into Space.

In this project, we propose to attempt this by examining lots of substorms over more than a decade using spacecraft together with networks of magnetometers (sophisticated scientific compasses) and radars in both the Arctic and Antarctic. The resulting stats will be compared with what we already know from much more limited observations and with the predictions of new and existing substorm theories and models. The outcomes will be knowing things like how likely a really big substorm is that could mess things up, as well as models to explain why and hopefully when that might occur.

As discussed in the Academic Beneficiaries section, there are numerous institutions that will benefit from this research. The overarching objective, to determine the energy partitioning within the substorm, and thus what quantity of energy is deposited into the Earth's ionosphere in the form of particle precipitation and Joule heating, is of paramount importance to those interested in the effects of Space Weather on our everyday lives.

Modern society is increasingly reliant on space-based technologies for their everyday lives and substorms have consequences on modern technological infrastructure in the Space and Energy sectors. These include damage to satellites, especially from surface charging, and disruptions to satellite communications and navigation due to ionospheric absorption and scintillation, to electricity supply due to electrical currents induced in the ground from ionospheric currents, and to oil and mineral prospecting due to geomagnetic field fluctuations.

Such so-called 'space weather' hazards are now considered to be sufficiently important to have been included in the latest UK Government National Risk Register. Providing information directly relevant to predictive space weather modelling efforts is the first step towards providing advance warning for low-frequency, but high-consequence events such as those identified by the top UK and US Science Advisors Holdren and Beddington who warn "The potential total cost of an extreme Space Weather event is estimated as $2 Trillion in year 1 in the U.S. alone, with a 4-10 year recovery period".

The Meteorological Office is responsible for providing space weather predictive capability and will directly benefit from the improved knowledge of the radiation belts that this project will provide. The Global Positioning System (GPS), and their European counterparts in Galileo, may be a primary benefactor of our research. The loss of particles into the ionosphere leads to large and currently unpredictable changes in the density of the ionosphere. The accuracy of location information provided by GNSS is significantly degraded during periods of rapid ionospheric change that result from the direct action of substorm and radiation belt dynamics. Many industries rely upon GNSS/GPS for their remarkable precision timing to 100 billionths of a second, synchronizing networks, computers or instruments. GPS technology is also used heavily in precision farming, including spraying and harvest, for snow removal in the US, and for vessels to determine their location precisely at sea anywhere on the globe. More generally, the effects of space weather can be felt in all activities that use space-related assets. For example, during the October-November 2003 geomagnetic storms the effects of space weather were included in a US National Weather Service report for the first time.

The research and professional skills that the two PDRAs will develop during this project will be in computational programming, the processing large datasets and clear scientific reasoning, written skills in the form of reports and publications, which are all applicable to many employment sectors.