Hot science: Cold prevention at IC

I’ll warn you at the outset that this is rather a navel-gazing article, as the topic for today’s story has been chosen for somewhat ulterior motives. I’ll reveal those motives at the end, when it’s time for some editorialising. In the meantime, it’s high time for an explanation: how could the ionosphere and the 2004 tsunami possibly be linked? 

On the face of it, it is hard to see how one might affect the other. The 2004 tsunami (triggered by a magnitude ~9.2 earthquake off the coast of Sumatra on the 26th of December) powerful as it may have been, occurred at sea level. The ionosphere, an electrically conductive layer of the atmosphere (the highest one, in fact) lies far above, between 85-600 km altitude. And though it forms the upper edge of the atmosphere, potentially linking it to events lower down, it is also the lower edge of the magnetosphere – the bubble-like region which Earth’s magnetic field carves out of the solar wind, a flow of plasma streaming outwards past us from the sun. The ionophere’s location and conductive nature means that changes in the solar wind and magnetosphere, such as those associated with aurorae, can have significant effects on the ionosphere. 

Another main cause of change in the ionosphere is also due to the sun: radiation. The ionosphere is electrically conducting because radiation at frequencies from UV and above ionises the neutral atoms, leaving a cloud of ions and electrons. Though these attract each other, and so should potentially recombine, the atmosphere at ionospheric altitudes is so tenuous that this cloud of charged particles can persist for long times, as a plasma, providing the generation mechanism – the sun – is visible, offsetting any losses due to recombination. At night, when the sun has no effect,  the number of charged particles decreases greatly. Some of you may have had practical experience of this, if you listen to long-wave radio stations: the signals bounce off the ionosphere, at an altitude where the number of free electrons floating around causes that layer to become opaque to radio waves, and act like a mirror instead. As this altitude changes over the course of a day, it affects the range of radio signals: a higher layer means signals from further away can be picked up. 

However, ionospheric changes are also due to atmospheric effects, which may in turn be due to changes all the way down at the surface. And it’s this type of mechanism which American researchers publishing in the Journal of Geophysical Research a few weeks ago think might explain their observations. They were using the Arecibo radio dish on Puerto Rico to probe the ionosphere around the time of the tsunami, and found that  abut 25 hours after that event, an unexpected rise and fall in one ionospheric layer occurred. Unusual, because it occurred at night, and when there was little magnetospheric activity, immediately ruling out two of the above causes for ionospheric changes. Nor did it look like this was due to waves caused by a storm – there were none nearby at the time. Instead, Lee et al. suggest that the tsunami waves on the ocean caused associated gravity waves (nothing to do with space-time: these are waves due to fluid parcels being displaced into regions of different density – gravity or buoyancy acts as a restoring force, causing oscillation about an equiibrium) in the atmosphere. The effects of these gravity waves leaked into the ionosphere, causing the variations seen at Arecibo, and also by various GPS satellites, which are sensitive to the electron content of the ionosphere. 

What has this got to do with the Science and Technologies Facilities Council (STFC), the body which funds astronomical, space science and particle physics research in the UK? Keen readers of science news amongst you may have spotted that the STFC is going through a funding crisis at the moment – there’s an £80 million hole in its budget, which threatens swingeing cuts in many areas. Notably in the research area which the above study belongs to: STFC has said it will “cease all support for ground-based solar-terrestrial physics facilities”. This is where I need to confess something: I might not be entirely objective here, as my research area involves looking at part of the magnetospheric system. My area does not directly look quite so threatened, yet for various personal reasons, I see the loss of UK solar-terrestrial physics ground facilities as a blow. 

You see, the UK is really rather good at solar terrestrial physics, and puts its facilities to good use. I almost went to do my Ph.D. at Leicester, a particularly strong institute currently under threat, as I was attracted to their way of viewing the complicated interactions from the solar wind all the way down to the atmosphere as one cohesive system, which needs to be treated as such to be understood. The above study is a nice example of energy transfer between regions covered by different funding councils: the STFC above, and the Natural Environment Research Council below. At a time when we recognise the need to understand the processes affecting climate, surely it is foolish to squander world-class expertise in an area interacting with climatic science, merely because the funding councils define a remit boundary at a particular altitude, a boundary which is flouted in at least this case, and likely in  others?

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