Sun-Earth Day Lecture

Wednesday 17th April 2024

The NASA/ESA Sun-Earth Day lecture entitled ‘Space Weather- Electromagnetic Threats from the Sun’ was given at the end of Lent Term by Professor David Southwood. Pupil Talitha S wrote the following review:

On the evening of Tuesday 19th March, we were lucky enough to be visited by Professor Southwood, a specialist in space weather, who delivered a brilliant talk on this fascinating and relatively new area of science. Space weather, a range of electromagnetic events that occur as a result of changes on the Sun’s surface, has only been recognised as its own area of study in recent years, but certain scientists have been researching the field for many years prior to its official recognition.

It is Carrington who is universally acknowledged as being the first person to recognise this field of study, in 1859: however, this is not strictly true. Carrington was making observations of the Sun, drawing and documenting sunspots, when he noticed a rare event known as the white flare effect. This emitted a huge quantity of gamma rays causing large, unexplained changes to the Earth’s magnetic field. This is known as the Carrington event and meant that the aurorae, also known as the Northern and Southern lights, were visible all around the globe, rather than in their more usually limited ranges.

However, it was really Balfour Stewart who discovered space weather as he proposed that there could be a connection between solar disturbances and the electric currents and magnetic disturbances on Earth. At this time, his theory was denied by many other scientists, including Lord Kelvin, who believed it was impossible that Earth could be affected by solar activity due to the great distance between the two objects.

Following this, in 1899, Kristian Birkeland, who lived in Norway, aimed to learn what the aurora truly was as during this time it was believed to be a meteorological event, originating from within the Earth’s atmosphere, but Birkeland thought this was inaccurate. Following an expedition through Norway to try and find the true cause of the aurora, Birkeland believed that they were formed by electrons from the Sun hitting the Earth’s atmosphere, and we still believe this to be true today. For his time, however, this was an incredible discovery, especially considering that electrons had only been discovered two years prior to the expedition. This discovery proved that aurorae were not meteorological occurrences, but space weather events as they occur much higher in the atmosphere than the maximum height of meteorological events. Birkeland wrote up his hypothesis as a book which he published in French.

Professor Southwood then moved on to discuss his own work in the field of space weather. Southwood studied at Imperial College in the 1960s, looking at interplanetary magnetic fields. From here, he proceeded to study in Los Angeles for a short period of time before returning to Imperial College in 1971. Here he met a fellow enthusiast in magnetometers, instruments which measure the changes in these interplanetary magnetic fields. They formed a partnership to help improve their research in the field and the pair managed to build a chain of magnetometers all across the northern hemisphere, which were used to predict changes in the Earth’s magnetic field due to the aurora. They then were able to sell this data to six oil drilling companies for a six figure sum each year, as these companies need real time guidance on big changes in the Earth’s magnetic field as their drills are guided by this field and therefore the aurora can interfere with their navigation beneath the surface of the Earth. Without this information, their work would be far less productive.

Finally, Professor Southwood concluded his talk by discussing the dangers which space weather poses to us on Earth. These included interference with the national grid, blocking radar systems on ships and communication systems using radios, and interruptions of certain forms of transport including trains, aeroplanes, and driverless vehicles. It’s amazing to think that these far off events have very real effects here on Earth, and certainly gives food for thought.

Talitha S


About the Speaker

Professor David Southwood CBE is now a Senior Research Investigator at Imperial College, and a Non-Executive member of the UK Space Agency Steering Board. He had an academic career in Britain and USA, eventually becoming head of Physics at Imperial College, London. From 2001 to 2011 he was the Director of Science and Robotic Exploration at the European Space Agency (ESA).

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