DETERMINING AND PREDICTING THE SIZE AND ONSET TIMES OF SUBSTORMS

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The Sun's influence on the Earth goes well beyond gravitational attraction and shiny light and heat down on the Earth's surface; the Sun and Earth are connected by a stream of charged particles that is constantly flowing off the Sun and becoming trapped in the Earth's magnetic field. These charged particles bring with them the Sun's magnetic field, which can join up with the Earth's field, causing those trapped charged particles to become energised and to fly along the Earth's magnetic field into the atmosphere. When these particles hit the atmosphere, they cause it to glow in spectacular light displays that we call the aurora. The Earth is protected from most of the particles coming off the Sun by its magnetic field. As it expands out into space, it is deformed by the charged particles flowing off the Sun impacting upon it. It forms a bullet-like shaped region extending 60,000 km in front of the Earth, and over 600,000 km behind the Earth and known as the magnetosphere. As the solar particles and magnetic field hit the magnetosphere, it absorbs energy, storing that energy in the magnetic field behind the Earth. This store of energy is unstable, and eventually it is released, energising charged particles in the magnetosphere to create bright aurora in a process known as a substorm. These substorms happen three to four times per day, lighting up the night sky in the northern and southern polar regions for hours on end. To an observer in the right place on the ground, the whole of the night sky will light up over half-an-hour, before slowly fading for another hour or so.Whilst displays of substorm aurora are stunningly beautiful, they are far from benign. The particles associated with them can drive extremely large currents through the atmosphere that can cause other currents to flow on the ground. These currents can cause damage to electrical equipment and power networks, potentially leading to blackouts across large swathes of the Earth's surface. The energisation of charged particles in space can be hazardous to spacecraft, potentially causing millions of pounds worth of damage in a matter of seconds. As such, in a world that is increasingly reliant on space-based and electrical technology, these substorms represent a very real risk. Scientists also believe that these events can cause changes in the upper atmosphere that can affect its chemistry and potentially impact on climate, but as yet this effect is poorly understood owing to a lack of necessary observations.Despite being known about for thousands of years and studied in detail since the turn of the last century, we still are unable to accurately predict when and where these space weather events will occur. This is a major hurdle in space weather science that has remained a problem in this field due to a combination of lack of data and lack of the necessary tools to properly analyse this data. However, we are now in the best position to date to address these issues. The new research proposed in this project will combine datasets that have been collected over the last 20 years and answer the questions "when will these events occur?", "what will their impact be?" and "what controls them?". By answering these questions, we will be able to understand what we need to know in order to predict when these events will occur and what there impact will be.