May 21: pub!

It's 21 May, a very significant date. In my PhD thesis I analysed X-ray data from three solar flares, on 10 April, 21 May and 5 November 1980. The data had been collected by the Hard X-ray Imaging Spectrometer (HXIS) on the SMM satellite.

At that time we believed that hard (penetrating) X-rays from the Sun would come from the ends of magnetic loops (like those shown in the accompanying picture of the Sun in ultraviolet light), where they meet the dense solar atmosphere. HXIS showed us for the first time where on the Sun the hard X-rays were coming from. Sure enough these three flares displayed X-rays coming from pairs of points on the Sun, presumably the two end points of the loops involved: "footpoints". It would have been a big surprise if X-rays had come from above the surface - although in due course this too was seen. In Glasgow we weren't the first people to look at these footpoint observations but we tried to see what more they could tell us about the workings of flares.

The 21 May flare was one of the most intensively studied at that time. It was a big (X-class) flare, it did lots of different, interesting things and was inspected by several leading edge instruments, like HXIS. So many people wrote articles on aspects of this flare that it eventually played the starring role in its very own review article, where two famous solar astronomers summarised the various studies and drew them all together.

Many individual solar flares have been important in our developing understanding of these events: the first big flare seen in some new instrument, a flare that did something in a particularly simple way so that cause and effect seem clearer than in most cases, a flare that did something dramatic never seen before.

Over the decades there have been many such significant events. This was useful when I was young and frivolous. Today, for example, we could say, "it's the anniversary of the 21 May 1980 flare. We need to celebrate this - let's go to the pub!" In fact, if we scoured the solar physics literature we could probably find a solar flare to celebrate on most days of the calendar, especially now a couple of decades on: 13 January, 20 January, 23 February, 24 May, 3 June, 7 June, 14 July, 28 October....that's enough, you get the point, and I'm sorry so few of them have nice web resources and so many of the links are technical. Maybe that should be a wee job for somebody: "Flare of the day" blog. Anyway we never needed to wait very long to have an excuse for a wee pub visit, and if we really needed an excuse we could probably scour the literature and find somebody with their own wee solar observatory, lost and forgotten in the woods or clinging to some unvisited mountainside in some far-off and exotic land, who had observed a flare on that particular date.

Anyway, nowadays those pub visits are much rarer. We probably only used a famous solar flare as an excuse on a few occasions, to be honest - most of the time we didn't worry about excuses. But as I headed home on the bus this beautiful May day, I spotted lots of people sitting outside enjoying a beer or a glass of wine and I was glad to see that the X-class footpoint flare of 21 May 1980 is still celebrated vigorously.

Image: NASA Solar Dynamics Observatory AIA instrument ultraviolet image of solar loops from January 2012

Beyond the End of the World

I'm a sucker for the movies of Werner Herzog. I love his tales of overweening ambition, of people driven to places they shouldn't go, of characters who will never fit in. I'm hypnotised by Aguirre's awful thrust for Eldorado, though boats cling mysteriously to the treetops and his brutalised followers are cut down by attackers so implacable and faceless we can't even call them enemies. We know he can only finish up alone on the raft with the monkeys but that somehow makes his raging insanity all the more beautiful. Wisconsin is just as strange and hostile a destination for the hapless Stroszek ("one of the strangest films ever made"). The - comparatively - charming Fitzcarraldo drags a steamboat over a mountain to become a rubber magnate solely so that he can bring live opera to the jungle.

It makes complete sense that Herzog should turn his attention equally to real-life examples of such ambition: the man who dreams of floating above the canopy of the rainforest, the man who lived among grizzly bears, the people seeking secrets of the planet and of the universe in the Antarctic. He can't resist those characters whose ambitions take them places you shouldn't go, where the possibility of death is never far away or where the human body really cannot survive unaided. They're nicer people than Aguirre, usually cannier too, but restless dreamers nonetheless.

I haven't seen his science fiction movie, Wild Blue Yonder but there had to be one. Most of the Universe is much more hostile even than Antarctica and the exploration of outer space is one of the hugest of Herzogian projects. On Mars, for instance, there are landscapes and sights as strange as anything even in Fata Morgana: the huge dust devils, for instance, or the pink, streaked sand dunes of the polar regions.

In the solar physics community we're excited that ESA have at last given the Solar Orbiter mission the go-ahead. In the UK we're happy that it will be built here.

Mercury is the planet nearest to the Sun. On the day side of Mercury it's hot enough to melt lead. Solar Orbiter will go closer to the Sun than Mercury, and closer than any previous spacecraft. At its closest the Sun will be almost 13 times brighter than it is here on Earth. Heat poses a major challenge to the engineers so Solar Orbiter's instruments will peek at the Sun through holes in a heat shield, designed to keep the rest of the spacecraft at a stable temperature. The instruments will be pointing at the Sun so they themselves will have to cope with the intense sunlight, as will the solar panels that will provide electricity.

Solar Orbiter is venturing into a region of the solar system unexplored since the 1970s. Radiation (cosmic rays) accompanies the disturbances that travel away from the Sun, and is also produced at the Sun during solar flares. The level of radiation inside Mercury's orbit is uncertain but it will certainly be greater than here at Earth and the electronics will have to keep functioning in spite of this. The very phenomena Solar Orbiter aims to study will also make life difficult for it.

Solar Orbiter will be designed and built to meet these challenging conditions but it is exploring a distant, alien region of space: a dangerous place. Lots of brainpower and planning, as well as hundreds of millions of Euros, will be spent building, launching and operating it. Nobody's physical life will be in danger and it will be planned and operated cannily, without hubris. Solar Orbiter will not spin off out of the solar system, alone with the space monkeys. Nonetheless the allure of this dangerous, unexplored region of space makes me think of these crazy dreamers of the Herzog movies. And maybe there's a little of that crazy lust for dangerous places somewhere in the mind of even the soberest of space scientists.