First name: Andrew
Last name: Coates
Title: Reader in Physics, Head of Space Plasma Physics
Organization: University College London, Mullard Space Science Laboratory
Address: Holmbury St Mary, Dorking RH5 6NT, UK
Work: phone: 01483 204145
Work fax: 01483 278312
Mobile: 07788 448318
Talk title: What is space weather and why is it important?
Date of delivery: 07/09/01
Session organiser: Physics and Astronomy Section
As well as heat and light, the Sun emits a million tonnes of hot 'solar wind' per second on average. But the average picture does not always hold. During brief 'solar flares' the Sun emits bursts of X- and gamma- rays, and sometimes protons and electrons moving near the speed of light which can reach Earth in less than an hour. Huge amounts, tens of billions of tonnes, of charged solar material from events called 'coronal mass ejections' can disrupt the solar wind and buffet Earth's magnetic shield days later. Energetic cosmic rays from beyond our solar system can punch though the shield too, reaching the Earth's atmosphere. And while we recently passed the solar maximum, we are not even safe at the minimum of the 11-year solar activity cycle.
All of these 'space weather' effects can have important implications for humankind. In space, they can cause problems for satellites and astronauts, on the ground, power systems can be affected, and in the atmosphere between, there are effects on aircraft and on climate. There is much current interest in understanding these problems and in predicting when they are likely to happen.
The key to predicting space weather events is an understanding of the science behind space weather. At the moment space weather prediction is at the same state as terrestrial weather prediction was 50 years ago. To improve this we need to understand how and why continuous and impulsive emissions from the Sun occur. We need to understand how they propagate between Sun and Earth, and how our magnetic shield is penetrated. We need to understand the effects of solar wind changes on the Earth's magnetosphere and radiation belts, where satellites used in our daily lives are stationed and where 'killer' relativistic electrons are found. And we need to understand the coupling all the way through from the Sun to our atmosphere.
Now, several international (European, American, Japanese and Russian) scientific space missions are studying the chain of events from Sun to Earth. Staring at the Sun like SOHO and TRACE, measuring the upstream solar wind like ACE and Wind and inside our magnetosphere like Cluster, Polar and Geotail, the results are helping us understand the coupling processes. For example, the average electrical power incident on the Earth’s magnetic shield is about 3 million megawatts, equivalent to mankind's current energy consumption, corresponding to only 40kg of solar wind material per second. Only a few percent of this energy leaks in via 'magnetic reconnection' - an explosive small-scale plasma process which results in magnetic field being pulled over Earth's magnetic shield like peeling a banana and particles entering along punctures in our shield.
A search for understanding is vital. But we can also use the knowledge we have so far to perform applied research and provide forecasting for specific problems. For example, at MSSL we are working on practical applications of solar and space plasma physics for space weather users. First, we have two contracts part funded by the insurance industry as part of the Tsunami initiative, one to study satellite failures and the other to build a 'black box' detector for commercial satellites. Second, we are working with Virgin Atlantic Airways to measure and understand radiation in aircraft cabins.
In this presentation we will look at four main questions: (1) what is space weather? (2) what causes space weather? (3) what effects does space weather have? and (4) what are we doing about space weather?
Along the way we will see spectacular movies of the Sun's effects, look at the effects of huge solar disturbances including this year's record solar flare, look at exciting new results from Cluster and see what is the 'state of the art' in space weather prediction. Also, for the first time in public we will present results from our work on space environment prediction and diagnosis for the satellite insurance industry.
The key finding to be presented (although much of the talk is general) is that we can, with a reasonable level of skill, predict the intensity of 'killer' electrons in the Earth's radiation belts using only a few measured parameters, and therefore predict and analyse dangerous conditions for satellites.
Even after decades of study, only a few aspects of space weather can be predicted. 'Killer' electrons can cause danger for satellites on which we depend in our daily lives. A new website which can now predict dangerous conditions for satellites, using a 'red/amber/green' traffic light system, will be unveiled. In addition, new results from Cluster will be presented which will help us understand the magnetic shield's response to space weather events and we will show results from Cassini which reveal the effects of solar activity near Jupiter.
We depend on space for communications, weather forecasting and positioning on the Earth's surface. Each applications satellite costs some $250 million and is insured. We have an increasing volume of air travel and a tendency to use higher altitudes and polar routes. All of these can be affected by space weather, making this an important and relevant topic.
The next step is to improve the skill of predictions and to broaden the range of space weather effects that can be predicted.
Many research groups are active in solar and solar-terrestrial physics (see RAS MIST webpage at http://www.nerc-bas.ac.uk/public/uasd/mist.html, solar groups listed at http://www.mssl.ucl.ac.uk/www_solar/solarlinks.html ). UK groups are playing lead roles on the SOHO, Cluster and Yohkoh missions and are involved in many other space missions and are also strong in data interpretation, modelling and theory.
Several UK groups are involved in space weather related work. The studies at MSSL involving the insurance industry and airline companies are particularly relevant to the BA meeting theme 'Science and Society'.