Antenna: Weathering the solar storm

The Sun’s violent activity can jeopardise infrastructure and lives worldwide, but thanks to UCL scientists, predicting and preparing for these outbursts is on the horizon


If you were to ask most people to name the sort of items that they would expect to be included on the UK National Risk Register of Civil Emergencies, chances are that they would probably guess, correctly, that terrorist attacks, flooding and flu pandemics feature prominently.

It is much less likely, however, that they would suggest that space weather appears on it too. And yet it does.

Although the government sees an outbreak of severe space weather activity as a “high impact, low probability” event, it has judged it to be of sufficient risk to add to the register and to ask departments in charge of critical infrastructure to examine its resilience in the face of such an event.

On top of that, the government has provided funding for a new Met Office Space Weather Operations Centre, which opened in October 2014, and launched the UK Space Weather Public Dialogue to find out what the public thinks about space weather and its possible impacts here on Earth.

The answer is blowing in the wind

So what exactly is space weather? Popularised in the 1990s, the term describes the conditions in space, near the Earth, governed by the Sun’s constant release of charged particles known as the ‘solar wind’.

Periods of peak solar activity give rise to what are called ‘severe space weather events’, where the Sun produces phenomena such as solar flares and coronal mass ejections (CMEs) that interact with the Earth’s upper atmosphere and surrounding magnetic field, often to dramatic effect.

The best place to explore the science behind these phenomena and their potential impact on Earth is not a lab in London; instead, you need to pay a visit to a mansion perched majestically on a hill in the Surrey village of Holmbury St. Mary.

Journey to the centre of the Surrey countryside

UCL’s Mullard Space Science Laboratory (MSSL) is the home of UCL Space & Climate Physics, which is the largest university-based space research group in the UK. In addition to producing internationally recognised research, MSSL brings together scientists and engineers to build satellites and spacecraft instruments.

Professor Louise Harra, Head of the Solar Physics Group at MSSL, says that there are clear advantages to having such expertise under one roof. “We have two groups here — one is involved in solar physics and understanding the details of the Sun, while the other focuses on plasma physics, which involves understanding the magnetosphere both on the Earth and other planets. So the skillsets are quite different, but they’re extremely complementary.

Artist‘s concept of the Hinode spacecraft in orbit around the Earth with an active Sun in the background. Credit: JAXA

“We’re lucky here in that, being just down the corridor from one another, we can learn from each other and make sure that we get the best science out of each mission.”

Professor Harra is currently involved with a Japan/US/UK space mission called Hinode as Principal Investigator for the Extreme-Ultraviolet Imaging Spectrometer (EIS), one of three on-board instruments. Built by an MSSL-led consortium, the EIS measures the flow velocity of solar particles, as well as the temperature and density of the solar wind.

“Hinode, which means sunrise in Japanese, has been described as the Hubble telescope of the Sun,” says Harra. “It observes the surface of the Sun in great detail, seeing where magnetic fields have been created and how those produce the activity that we see.”

“Solar flares are very fast releases of energy across pretty much the whole electromagnetic spectrum, while coronal mass ejections are these huge bursts of mass and magnetic field.”

Together, Harra explains, the two phenomena are the most dramatic aspects of space weather in terms of their effect on Earth. “Solar flares happen quickly and they’re very energetic, so you will get an impact from one within tens of minutes potentially. You’ll get particles accelerated to close to the speed of light that can come and hit the near-Earth environment.

“Coronal mass ejections take a couple of days to get here, but, again, those can have a big effect in the near-Earth environment where there are spacecraft orbiting the Earth.”

And should solar flares or CMEs reach Earth, a different scientific skillset will be required. This is where Dr Robert Wicks, joint lecturer at MSSL and the UCL Institute for Risk and Disaster Reduction (IRDR), comes in.

“We have a lot of expertise in space physics, the activity of the Sun and its impact on the Earth at MSSL,” he says. “But at MSSL we generally don’t have a huge amount of expertise in resilience and planning and risk — IRDR does have such expertise. So I’m trying to form that link to enable us to be leaders in the UK on preparedness and resilience for space weather.”

Illuminating precedents

History provides several alarming examples of the type of events that we may need to prepare for.

The first one in 1859 is known as the Carrington Event and is named after British astronomers Richard C. Carrington and Richard Hodgson, who independently became the first people ever to observe a solar flare.

The flare was followed by a CME that struck the Earth’s magnetic field, inducing a geomagnetic storm that caused the aurora borealis to be seen almost all the way down to the Equator. It was purportedly so bright in north-eastern parts of the US that people were able to read a newspaper by it. However, the disruption didn’t stop there.

The geomagnetic storm caused the failure of telegraph systems around the world, gave the operators electric shocks and, in some cases, caused the telegraph paper to combust.

“That’s the first real space weather event observed by the scientific community,” says Wicks. “We didn’t really piece it all together until well into the 20th century when we had launched satellites that could actually measure these things in outer space.”

Another major space weather event took place in March 1989, when a huge CME again hit the Earth’s magnetosphere, setting off a geomagnetic storm. On this occasion, though, it knocked out large sections of the power grid in Quebec, causing a black-out across the Canadian province that lasted nine hours.

Playing havoc with GPS

In the 26 years since the 1989 storm, there has been greater recognition of the potential impact of space weather on electrical systems and the steps needed to mitigate it. Unfortunately, though, it now poses a new threat to our infrastructure.

The increased radiation that comes with a severe space weather event changes the thickness of the ionosphere — the top layer of the atmosphere — which plays havoc with GPS.

Dr Wicks explains: “If you look through water in a glass and put a straw in, it bends. The same thing happens with signals coming from GPS satellites, and if those radio waves get bent by a thicker ionosphere then your Satnav will think you’re half a mile further east or west or north or south than you really are.”

“It’s not a disaster for most of us, but if you’re an airliner trying to land or a ship trying to avoid rocks, then these things can be really important.”

Clearly, our dependence on GPS is not going to end any time soon, so if we are to increase our space weather resilience, we need greater understanding of the Sun and its cycles of activity.

“If you imagine what Earth weather prediction was like in the 1970s, we’re perhaps at that level of understanding.”

The latest attempt to do this is the European Space Agency (ESA)-funded spacecraft, Solar Orbiter. The mission is set to launch in October 2018 and will provide the closest-ever views of the Sun, travelling in an orbit that will take it as close as 0.28 AU (1 AU, or astronomical unit, is the distance of the Earth from the Sun).

There will be 10 scientific instruments on board Solar Orbiter — including the Solar Wind Analyser (SWA), which MSSL is leading on.

Dhiren Kataria is head of the In-Situ Detection Systems Group at MSSL and he and his team will work on the construction of the SWA. He says: “It consists of three sensors: a heavy ion spectrometer, a proton-alpha spectrometer and an electron analyser, serviced by a common Data Processing Unit.

“The first two are being built by a collaboration between the Americans and the French, with participation from MSSL, but the electron instrument is what we are building here.”

SWA is being built by a large international consortium from the USA, France, Italy and the Czech Republic, but the electron analyser is what we are building here.”

Where no one has gone before

Professor Louise Harra is co-principal investigator on one of the other on-board instruments. She says Solar Orbiter and its close orbit will provide a real leap forward in terms of understanding because it will allow scientists to measure the solar wind as it passes the spacecraft.

“The other advantage of Solar Orbiter,” she adds, “is that we will use this complex sequence of fly-bys past Venus and Earth — and that will give us enough energy to kick on out of the ecliptic plane, which is where all the planets lie.

“Once we get out of that plane, we can peer down at the poles of the Sun, which has never been done before as we haven’t been able to see them. The poles are really important for understanding the solar cycle and the dynamics creating the Sun’s magnetic field.”

Considering how close the spacecraft will get to the Sun, you would expect Solar Orbiter’s electronics instruments to be affected by all the solar activity — but Kataria and his team have taken this into account.

“We do lifetime tests on the ground to make sure that we understand how the instrument is going to behave with time once it’s up there. Solar Orbiter is a good example because it’s going to be up there for about 10 years.

“So we need to make sure that, with all the radiation that’s going to hit it, as well as the primary plasma, our detectors and our electronics can survive that solar lifetime. There are characterisation tests that are done on a representative set of technology to ensure that we can meet those requirements.”

Although Solar Orbiter won’t be launched into space until October 2018, that doesn’t mean that further work on space weather will have to wait until then.

“We’re building relationships with the British Geological Survey (BGS),” explains Dr Wicks, “and if we’re trying to measure the impacts of space weather, one of the easiest ways to do that is through the magnetic field, so we need to know what the local background magnetic field is very accurately and BGS does a great job of that.”

“We’re also working with the Met Office. They have the UK Space Weather Operations Centre up and running now and they produce a space weather forecast for the UK, so there’s questions we’re going to ask them, like: who gets this forecast? How reliable is it?

“At the moment, it’s delivered by a website and email — well, if the space weather causes the internet to go on the fritz for 20 minutes, that’s not necessarily the safest way to deliver that information!”

Harra agrees that we’re at the relatively early stages of predicting space weather. “If you imagine what Earth weather prediction was like in the 1970s, we’re perhaps at that level of understanding,” she says.

“We’re still not at the point where we can say, ‘Tomorrow at 6.30, there will be a storm from here’, but that’s where we want to get to. So we could envisage in years to come that there will be Earth weather and space weather forecasts and, hopefully, we’ll get to the point where we’ll be able to produce that quite accurately.” ■