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Teaching and notoriety


Mapping space weather
Antony Hewish Astronomer
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We had discovered that the interplanetary scintillation, as this twinkling is called – is caused by the solar wind – was stronger or weaker in different parts of the sky according to the time you made the observations. And that was because the solar wind contains disturbances in it and, in some directions, you get much denser solar wind than in other directions and this was, actually, related to solar disturbances. And I realised that you could use this twinkling, this scintillation effect, to map disturbances moving away from the Sun into interplanetary space, and we could map what they now call space weather.

Now, this was important, not just scientifically, but also practically because a great deal of damage is done to terrestrial orbiting satellites, things like communication satellites; when the Sun has major disturbances it produces blasts of much faster solar wind, which interact with the Earth's environment, the magnetosphere as we call it, and brings, accelerates energetic particles. And these can damage spacecraft orbiting the Earth; the energetic particles that are accelerated by these solar disturbances can penetrate equipment up there in… in things like communication satellites and actually knock them out of action. The electrons get… high speed electrons can get trapped inside the electronics, they're energetic enough to penetrate. And not only that, you get damaging X-radiation as well, high-frequency radiation and gamma radiation and UV, of course, and these things can damage human beings. They… they are radiation that can penetrate the human body, of course, and if you're doing something in Skylab and you happen to be drifting around in open space on the end of a umbilical cable, as they do, if you got caught in a disturbance like this, which could last several hours, you could get… you could suffer serious physical damage. And there's… there's a big research lab in Boulder, Colorado, in the States, which is set up simply to monitor space weather and to give… to give warning. I mean, they observe the Sun as closely as they can and they also have spacecraft orbiting and the idea is to try to detect disturbances, detect when disturbances are going to leave the Sun and… and rush across space. So that, for example, astronauts could be warned to hop inside again to get the screening effect of the metal of the spacecraft, space station, or whatever. Or if you're in a… in a satellite you could… you could control them, you might turn them into a safe… safe direction, just like on the ground you can, if you have a high speed wind, you can rotate structures so as they don't get damaged.

And this is a big deal… a big deal in the… in the States, they spent a lot of money on these things because it is important for practical purposes to know what space weather is doing. And I decided that if we made… if we could make maps of the scintillation over the whole sky fast enough, for example in 24 hours you could map the whole sky, then you could see from the scintillation in which direction solar disturbances were travelling and… and catch them before they reach the Earth. And… and you could have a space weather prediction service, just like terrestrial weather prediction, and this would be of great practical importance. And we were funded by the Americans to do some preliminary research on this and I'm now talking about which work going on in the 1990s. And… and we did some quite interesting work on… on mapping space weather patterns as they… as they came out of the Sun. But, with our equipment, we can only make one sky map per 24 hours because the antenna is fixed and that's not really quite rapid enough to make a good weather prediction service. To do that, you'd need a number of antennas around the Earth. Perhaps if you had four installations like we have at Cambridge at different longitudes, then you could compare the maps at all those, these sky maps, and… and catch these disturbances moving away from the Sun and map them rather better. But the Indians… you've been to India, you know all about their research, but I don't think you know much about what was going on at Ahmadabad where they copied my array but didn't do it terribly well, I have to say. And the idea was that they would also make maps of interplanetary weather and compare them with ours, and… but they never really got their show on the road.

And that whole programme ultimately fizzled out, but it… it produced a lot of PhD students… I mean, Graham Woan, for example, was the last person. He's studying gravitational waves now, and… or at least he will be, I hope, in the future. But that kept the antenna busy until the mid 1990s and I was really rather pleased about that, because here was this antenna which I decided was – when I designed it, it was designed to last for 5 or 10 years – was operating for about 30 years actually, finally, with Peter Duffett-Smith's modifications and with better electronics with it so that you could make maps, weather maps rather, on a daily basis.

And that kept me interested scientifically. We discovered many useful things and… and had many PhDs and publications about… about space weather and that was really my final original research. We did some… I'd… I had some research on theoretical work, on… on pulsars, but nothing, as it were, very… very world-shaking. We discovered that pulsars are affected by the interstellar medium on short timescales and so you can map moving clouds in interstellar space and that's quite an interesting thing to do. We did… we did that sort of work and I… I put some theoretical work into that using other people's data. I collaborated with the Germans at Effelsberg and… and wrote some papers with… with them, and that kept me busy in research. But, as… as you know, if you're a research scientist in Cambridge, you can't spend all your time doing research, you have to actually teach undergraduates. And teaching is always something I've enjoyed a great deal.

Antony Hewish (1924-2021) was a pioneer of radio astronomy known for his study of intergalactic weather patterns and his development of giant telescopes. He was awarded the Nobel Prize for Physics in 1974, together with fellow radio-astronomer Sir Martin Ryle, for his decisive role in the groundbreaking discovery of pulsars. He also received the Eddington Medal of the Royal Astronomical Society in 1969.

Listeners: Dave Green

Dave Green is a radio astronomer at the Cavendish Laboratory in Cambridge. As an undergraduate at Cambridge his first university physics lecture course was given by Professor Hewish. Subsequently he completed his PhD at the Cavendish Laboratory when Professor Hewish was head of the radio astronomy group, and after postdoctoral research in Canada he returned to the Cavendish, where he is now a Senior Lecturer. He is a Teaching Fellow at Churchill College. His research interests include supernova remnants and the extended remains of supernova explosions.

Tags: solar wind, interplanetary scitillation, satellites, radiation, antenna, pulsars

Duration: 7 minutes, 30 seconds

Date story recorded: August 2008

Date story went live: 25 June 2009