Forecasting space weather

Tuesday 6 November 2001

A study by St Andrews solar scientists to establish why one of the most dramatic forms of solar phenomena occurs could lead to a significant contribution to the development of ‘space weather forecasts’.

Such forecasts predict whether ‘solar eruptions’ may have hazardous effects, such as radiation exposure to astronauts in orbit, short-circuiting of satellites in space and power loss on Earth.

The project, which has just received over £65,000 funding from the European Commission, is led by Dr Thomas Neukirch and his colleague Dr Jean-Claude Thelen at the University of St Andrews.

Their research will involve mathematical modelling of such phenomena using sophisticated analytical techniques and computational experiments on ‘supercomputers’ to explain and understand observations of the Sun from satellites in space and observatories on Earth.

The study will look at how and why sudden eruptions of Solar Prominences occur so that predictions of future eruptions can eventually be made.

The project is part of a much larger research effort of the St Andrews University Solar Theory Group to understand the Sun’s magnetic activity, an area in which the group has gained a world- class reputation over the past 30 years.

The prediction of ‘Space weather’, in principal, works in the same way as predicting weather on Earth. At present there is roughly a 2 to 4 day ‘warning period’ of eruptions before they will reach the Earth which allows, for example, a change in levels of power supplies so that expected power surges would not cause overloads. Such forecasting is already beginning to take place, using observations of the Sun taken by spacecraft such as the joint European-US SOHO mission.

“Prominences can exist for days or even weeks without showing too much activity and then erupt suddenly. During these eruptions, prominence material can be ejected into interplanetary space together with the supporting magnetic field. Such events are called Coronal Mass Ejections (CMEs),” said Dr Neukirch.

“If a CME happens to hit the magnetic field of the Earth, the so-called magnetosphere, the enhanced number of energetic particles it produces close to the Earth not only causes enhanced auroral activity in the sky but can also be hazardous to astronauts in orbit, satellites and, in extreme cases, to electrical power lines on the Earth’s surface.”

“The aims of the project are to understand under which conditions prominences form in the corona, why they can be stable for so long and what causes their sudden eruption. We hope that by a better understanding of these questions we might in the long run be able to predict the location and time of prominence eruptions and CMEs. This may contribute to improving to forecast the so-called ‘space weather’ in a way similar to our normal weather forecasts.”

There are various theories as to why solar eruptions occur. A crucial role is played by the Sun’s complex magnetic field which is thought to provide the huge amount of energy involved in CMEs and prominence eruptions. The investigation of solar eruptions and CMEs is an increasingly popular study area in the field of solar science, both in the US and in Europe.

Apart from general scientific curiosity, the increase in interest is also due to the potentially damaging effects these events may have for astronauts in space, satellites and telecommunication. This makes forecasting of eruptions important for space agencies such as NASA and ESA; for companies insuring commercial telecommunications satellites, and , particularly in the US, for the military.

Mathematical modelling is crucial in this area, since as any prediction of future events is based on solutions of mathematical equations, using the current observations of the Sun as input. The St Andrews group is one of the largest in the world studying in this area of mathematical modelling of solar phenomena. Dramatic features such as solar eruptions whose influence extends from the Sun to well outside the Earth’s orbit have challenged scientists to develop better scientific models of what is going on inside and around the Sun, although great advances have been made in their understanding of the Sun in recent years.

Solar Prominences, which can often be seen by naked eye during solar eclipses, have been studied for several centuries, but their association with the Sun has been a matter of dispute until 1860. With the development of better observational instruments in the twentieth century, it became clear that prominences are a common feature of the solar atmosphere, and that they can eventually erupt and be expelled into interplanetary space. The term Coronal Mass Ejection was not mentioned until the 1970s, when viewing of Sun and its surroundings was made possible through satellites, and it became soon clear that CMEs and prominence eruptions are closely linked phenomena. Solar eruptions usually also cause enhanced solar emission in visible light, X-rays and radio waves. Such events are called solar flares.

In April this year, the largest ever observed solar flare occurred, causing widescale auroral displays witnessed on Earth (Scottish pics available). The auroral displays are caused by atoms glowing in the atmosphere after being hit by highly energetic particles from the magnetosphere. The previous record was for a flare which occurred in 1989, causing the failure of a powergrid in Quebec, and a subsequent blackout for parts of Canada and northern USA.

Dr Neukirch and Dr Thelen are part of the Solar MHD (Magnetohydrodynamics) Theory Group at St Andrews – a large group of applied mathematicians who study the Sun using mathematical modelling techniques and observational data from spacecraft such as SOHO (located between the Sun and the Earth) and ground-based observatories.

Solar MHD is the study of the subtle interaction between the Sun’s magnetic field and its plasma interior or atmosphere. The group currently investigate a large number of dramatic solar phenomena including sunspots, coronal heating, solar flares and magnetic instabilities.



Issued by Beattie Media on behalf of the University of St Andrews Contact Gayle Cook on 01334 467227, mobile 07900 050103, or email [email protected] Ref: Press Releasessolar prominences pr 051101.doc

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