Bowler, Livermore: Meeting report
2: Contours of geomagnetic field intensity
from CHAOS-4 at epoch 2010 to degree 13 on
Earth’s surface. The maximum rate of change of
intensity is currently ~100 nT/yr.
The field at the Earth’s surface (shown in figure
2) is weaker and not uniform, with relatively
low strength at the poles, strong flux patches
under Canada and Siberia and Africa, plus a
growing region of reverse flux in the southern hemisphere known as the South Atlantic
Anomaly (SAA).
He went on to describe the complexities of
modelling the heat flux carried outward by the
convection and how the magnetic field is generated by dynamo action. Thermal convection
occurs only if the heat flux passing through the
core is greater than the heat flux that can be
conducted up the adiabatic temperature gradient; recent results from the high-pressure physics community indicate that much more heat
can be carried by conduction than previously
thought. At present, buoyant lighter material
is being released at the inner core boundary
(compositional convection) which can drive the
flow powering the dynamo. However, thermal
history calculations suggest that the inner core
may be less than 1 billion years old. If this is the
case, the question arises as to what was driving
the dynamo before this compositional convection from solidification of the inner core was
available; magnetic field records from ancient
rocks extend back at least 3.5 billion years.
Possible solutions are that radio­activity was an
important heat source in the core, or that light
material was being extracted at the core–mantle
Meeting report Sue Bowler and Phil Livermore report from a
boundary, driving compositional convection
meeting about space weather, space climate change and their wider
from above. Simulations generally use one or,
economic effects, from academic and industrial perspectives.
at most, two energy sources and all the models are more diffusive than the real core out of
he magnetic field within and at the sur- in the Earth’s iron core. In the fluid
computational necessity. Convecface of the Earth (figure 1) and the effects outer core, flow of the conducttion in rapidly rotating systems
of the magnetosphere in space are dif- ing molten iron works like
takes the form of spiralling
ferent aspects of the same phenomenon, yet a dynamo – the geodycolumns shown in fighistorically they have been studied by different namo – to produce and
ure 3. This pattern of
communities of scientists. Advances in observa- maintain the field.
convection is known
tional capacity and data analysis are bringing Convection arising
to be good at generating magnetic
the scientific questions closer together and, as a from the freezing
fields, particuconsequence, researchers in magnetosphere, ion- of the inner core,
osphere and solar–terrestrial physics and in geo- the slow cooling
larly dipole-dommagnetism now have much more in common. of the Earth as a
inated fields such
This meeting in Leeds in June 2012 on “Predict- whole, and posas the Earth’s
magnetic field,
ing deep Earth processes and impacts on space sibly radioactive
climate” was organized by Phil Livermore (Uni- heating, produces core
and models with
versity of Leeds), Richard Holme (University of flows at velocities typically
this pattern of
convection do a
Liverpool), Kathy Whaler (University of Edin- 5 × 10 –4 m s–1 – slower than most
burgh) and Chris Jones (University of Leeds) to snails! Compositional convecgood job of simulating
explore common challenges and seek effective tion, tidal interactions and
the geodynamo. A recent critiapproaches to understand the Earth’s magnetic the precession of the Earth’s
cism of the current generation of
1: The magnetic field on the
field and its impact on human society.
axis also provide energy to the
dynamo models is that although
surface of the core shows
The conference began with some scene- dynamo, producing a field at the
they do produce flows as in figcomplex patterns; blue
setting. Chris Jones (University of Leeds) gave core–mantle boundary (CMB) shows flux pointing radially ure 3, in the models the thickan overview of the origin of the magnetic field of about 8 × 10 –4 Tesla (8 Gauss). inwards, yellow outwards. ness of the columns is controlled
Next steps for
space climate
research
T
A&G • February 2014 • Vol. 55 1.21
Bowler, Livermore: Meeting report
Space weather and
its effects
3: The Coriolis force (from Earth’s rotation) bends streamlines into twisted vortices: this is the
structure of flow that is anticipated in Earth’s core and ultimately responsible for generating the
geomagnetic field. Orange and blue colours indicate polarity. (C Jones)
more by artificial diffusive processes rather than
by the action of the magnetic field, which probably controls the column width in the Earth’s
core. So there is still a way to go before we
can claim that our models capture all the key
dynamics inside the core.
Geodynamo models are very useful for studying the dynamics of the core on millennial
timescales, roughly the decay time of a dipole
magnetic field. To study the growth and development of reverse flux patches such as the South
Atlantic Anomaly, we need to explore what happens on decadal timescales, and this is computationally challenging. However, progress is being
made and a new generation of models designed
to study the geomagnetic field on shorter timescales is being developed.
Space weather effects
Jim Wild (Lancaster University) then introduced the topic of space weather, which broadly
describes the effects of electromagnetic coupling
between the Sun and Earth, i.e. the solar wind,
magnetic reconnection, auroral activity and the
radiation belts. This coupling, and the changes
that take place when extra energy comes from
the Sun in the form of geomagnetic storms,
affect human society in many ways (see box
1.22
“Space weather and its effects”).
Geomagnetically induced currents (GICs) in
power grids have significant economic impact.
Solar storms can damage or cause failure in
transformers in the local distribution network.
Nationally, the UK electrical distribution network is becoming more complex and interconnected, making predicting and controlling their
influence more difficult. GICs also affect railway signalling and oil and gas pipelines.
During bad space weather, airlines avoid polar
routes; energetic particles preferentially precipitate in the polar regions, affecting not only
communications but also potentially increasing radiation exposure. Satellite navigation can
also be compromised, especially near the poles,
where sightlines to GPS satellites are limited.
There is considerable US–UK cooperation in
providing space-weather information but it is
challenging and expensive, involving processes
that are not completely understood. Industry
needs information that is good enough to act
on. While it is now possible to predict coronal
mass ejections (CMEs) and other solar activity
that will affect Earth because there are spacecraft monitoring the Sun, what the National
Grid and other infrastructure companies need
is an estimate of the severity of a given event, as
Space weather is always present in the form
of the solar wind, but is more damaging when
more energy comes from the Sun. Coronal
mass ejections (CMEs) involve around a
million tonnes of plasma moving at a million
miles per hour, leaving the Sun and arriving at
Earth between one and four days later. They
last for a day or two and when they reach
Earth they affect radio communications and
navigation, as well as inducing currents in
power grids, pipelines and other conducting
metal structures. CMEs arriving at Earth
can be forecast because there are spacecraft
between Earth and the Sun.
Solar X-rays arrive 8 minutes after leaving
the Sun and solar energetic protons arrive
between 30 minutes and 24 hours later; both
affect people’s health and interfere with radio
signals. Their speed of travel makes forecasting difficult, although satellites around Earth
can give a short-term warning of energetic
particles.
Power supplies can be affected by geomagnetically induced currents (GICs), which arise
from fluctuating electrojets in the atmosphere, which in turn produce a time-varying
magnetic field at ground level. While currents
are low, GICs have high voltages and impose
a DC signal on an AC circuit, with the possibility of harmonics resulting in half-wave
saturation and eddy currents. The effects are
worst in transformers at substations, which
experience direct degradation of insulators.
For example, during the Halloween storm
of 2003, methane, ethane, hydrogen and
ethylene were recorded bubbling out of the
insulation of some transformers while the
induced current flowed. Some transformers
damaged by storms continue to work, but fail
a month or so later.
Railways are also vulnerable to electrical
supply problems from GICs, especially where
communications and signalling rely on track
circuits. A strong geomagnetic storm will
induce currents in the ground that result in
signalling problems and even difficulties in
locating trains. Oil and gas pipelines also
suffer from induced currents, which interfere
with their anti-corrosion circuits.
Satellites and the web of technology that
depends on them are especially vulnerable to
well as the level of risk and the size of the event
in terms of the frequency and magnitude of the
magnetic field fluctuations at ground level with
time. That is where cooperation between space
and geomagnetism research is needed in future.
Mike Hapgood (RAL) then outlined UK polA&G • February 2014 • Vol. 55
Bowler, Livermore: Meeting report
space weather, which affects their magnetic
attitude control (i.e. their ability to know their
orientation) and induces surface and interior
charging. Episodes of high-speed solar wind
also add energy to the radiation belts and
increase satellite charging, as well as posing a
threat to air crew and astronaut safety.
Space weather can make the ionosphere
expand and become more dense at satellite
altitude, increasing drag on satellites, which
not only reduces their orbital radius but also
introduces errors in their predicted positions.
Around 6000 satellites have been launched in
the Space Age, and their accurate tracking is
of fundamental importance in order to avoid
collision. In addition, energetic particles can
affect software and hardware in satellites,
sometimes permanently. Interaction with hot
plasma can lead to surface charging, another
source of damage. The revenue losses are
potentially large: it costs $2m per year to rent
just one transponder on one satellite.
Air navigation is also vulnerable to spaceweather events. More energetic particles
around Earth lead to more ionic scintillation, which makes the GPS signal twinkle,
and GPS location less effective. Solar radio
bursts can also “jam” the signal. And space
weather can change the density of the upper
atmosphere, altering the orbits of navigation
satellites and downgrading the GPS resolution. The US Federal Aviation Authority
requires a GPS resolution of at least 50 m in
order for planes to fly, so a space-weather
event can bring flight restrictions. In addition,
the radiation dose for aircrew now has legal
and regulatory significance of which a key
measure is the neutron flux at 10–15 km altitude. The net result of this are diversions and
cancellations for travellers, although there is
a wider economic impact as fuel costs rise and
cargo volumes drop.
There are also potential wider effects, for
example those arising from GPS location
being unavailable for a few hours or days.
Emergency services and many day-to-day
web-based information services use GPS. In
addition, the combination of location and
timing provided by GPS has become important in international legal and financial transactions. Overall, a big geomagnetic storm is
estimated to cost the US economy $1–2bn,
and recovery from the loss of grid infrastructure could take between four and ten years.
icy developments in the field of space weather.
The focus of policy is on security and resilience
to space-weather natural hazards, bearing in
mind the critical dependence of our technological infrastructure and, especially, its interconnectedness, which could result in cascades of
A&G • February 2014 • Vol. 55 4: Severe space weather is as likely as a heatwave – and as likely to have an equally disruptive effect –
according to the UK government’s risk assessment, the National Risk Register of Civil Emergencies.
damage in a critical situation. In the UK, government works with industry – in part because
90% of the infrastructure is commercially
owned – and so needs good science advice in
order to prioritize funding decisions. The Space
Environment Impacts Group, started in 2010,
feeds into the National Risk Register of Civil
Emergencies for the Cabinet Office. Their information is based on peer-reviewed science and
uses a risk matrix (figure 4) that assesses the risk
of a severe space-weather event in the next five
years combined with impacts, such as loss of a
GPS service for a couple of days, which would
be a problem for emergency services, for example. This approach gives a strategic view, identifying knowledge gaps and boosting awareness
among government, industry and media – useful for such a young field as space weather. The
focus on risk also feeds into national space security policy and planning of response to major
events. It also poses questions such as what are
we monitoring and what can we forecast, so
that we can identify what is vital and how to
fund it. The positioning of space weather among
other potential civil emergencies means it comes
to the attention of government bodies such as
the Commons Science & Technology Committees and the Defence Committee.
Government wants to know what to expect –
and what science to fund – in the next five years.
One of the questions is whether the magnetic
models used in space weather are up to date?
Hapgood suggested this as something that the
research community could usefully address. It
is also helpful to assess the evidence from historical examples, where appropriate. The power
grid and other metal structures that are electrically grounded are at risk and Hapgood pointed
out that a repeat of the Carrington Event of
1859 would be very disruptive, but probably not
catastrophic, resulting in nationwide blackouts;
in areas of low population density, power could
be lost for a month or two. The effects of a 1921
storm on railways in Sweden and Russia and a
1938 event in the UK suggest that the worst case
would be a rate of change of magnetic field (dB/
dt) of 5000 nT per minute. It would be helpful
to know if changes to the Earth’s magnetic field
would affect this threshold, for example, and
if particular locations are at risk. We also need
to know how changes to the geomagnetic field
affect the morphology of the ionosphere.
1.23
Bowler, Livermore: Meeting report
As well as high-energy events, everyday space
weather affects high-frequency communications, proper function of the power grid and
corrosion control in pipelines, among other
issues for society and industry. These are highvolume, high-value products and Mike Hapgood and Alan Thompson are looking into their
dissemination via Lloyds reports. For the future,
Hapgood stressed that the STFC and NERC
Natural Hazards research strands are important, as are UK–US links and the SpacE weather
REsearch Network (SEREN).
Earth’s field from the inside…
Chris Finlay (DTU, Copenhagen) then spoke
about the International Geomagnetic Reference Field (IGRF) and its use in prediction. The
IGRF is a five-year model based on observatory
and satellite observations of the field, which is
freely available and applied in other disciplines,
such as space physics, directional drilling and
navigation. The model allows testing of ideas,
for example about the inclination of the internal
field in areas such as the South Atlantic Anomaly
(SAA), where a dipole field produces incorrect
ionospheric data. For space-climate predictions,
rather than the more immediate space-weather
forecast, it is important to look at major core
processes which alter the internal geomagnetic
field (for example, the westward drift and dipole
decline) as described by the IGRF model.
Vincent Lesur (GFZ, Potsdam) then focused
on the SAA, noting that it has persisted for at
least 300 years in its present form, drifting
slowly southwest. There is a suggestion from
archeomagnetic data that the SAA was more
pronounced in 1500 than in 1700, when it
appeared to weaken.
Susan Macmillan and Ciarán Beggan (British
Geological Survey, Edinburgh) then discussed
methods for prediction of the magnetic field,
with an initial focus on the SAA, which is a
dominant feature of current models and one
that determines the location of the radiation
belt footprints. The inner radiation belt comprises mainly high-energy particles, probably
from cosmic rays, and satellite operators need to
be aware of its position over the SAA in order to
protect sensitive instruments. Dipole models of
the field underestimate the SAA, which is currently getting bigger and moving westwards.
Patterns of flow on the core surface are a good
method of forecasting changes in the field,
although geomagnetic jerks, a poorly- understood phen­om­enon, can limit predictability.
Alex Fournier (IPGP, Paris) was unable to
attend but Phil Livermore (Leeds) presented
his talk about data assimilation in geodynamo
modelling, which brings together the physics of
the core with geomagnetic data. The data are
limited because the observed field is not only
filtered through the crustal field – but we only
know the (outwards pointing) magnetic field on
1.24
the core surface: it’s like doing weather forecasting using stations on the coast only. Some tests
were described in which synthetic data were
generated by a forward model and then a reconstruction was successfully attempted. However,
on short timescales linear prediction based on
secular variation performed better than the
assimilation method. Some studies suggest that
a limit for predictability of the internal magnetic
field is around 30 years.
Mervyn Freeman (BAS) considered the
ground-based magnetometer network, posing
the questions: how many should we have and
how much use are they? This data source records
slow changes in the internal magnetic field,
whose future prediction is a basic input into
forecasts of space climate. Although it is not yet
possible to predict future changes in the internal
field, we can extrapolate the IGRF models linearly on short timescales, up to about five years.
The UK contributes about 1 in 13 of the
world’s ~300 magnetometers, which are
coordinated internationally through INTER­
MAGNET and SuperMAG. Improvements in
this data service would come from having a
more coordinated network including variometer
data (to assess external and induced fields), from
better national and international coordination
and from having a stable network of magnet­
ometers. There is a further issue in the use of
the data: the internal models use only quiet field
data (in order to minimize external-field contributions). Developments in field modelling may
allow more data to be used.
…and from the outside
Malcolm Dunlap (RAL) discussed SWARM,
a space mission (that has since been launched
in November 2013) to measure the magnetic
field at around 500 km altitude. SWARM will
not only help identify with more accuracy the
internal field, but also the structure and dynamics of the external magnetic field, including the
effect of the ring current. The SWARM mission
is novel in its structure, comprising a constellation of three satellites, two flying in tandem and
a third on an independent orbit.
Alan Aylward (UCL) spoke about the thermal
ionosphere and the relevance of its modelling for
space weather. Any sort of forecasting or “nowcasting” – comparing real-time events as they
evolve with model predictions – needs a global
model of the upper atmosphere, which in turn
needs realistic driving forces. Models must deal
with a very wide range of parameters, for example, levels of oxygen and nitrogen, both as neutral and ionized species; temperature and winds
must be considered, as must a realistic means of
putting energy and momentum into the system.
Some useful data come from Super­DARN, the
Super Dual Auroral Radar Network, a network
of 21 high-frequency radars in the northern
hemisphere and 11 in the south. The upper-
atmosphere models are empirical, relying on, for
example, the high-latitude convection measurements provided by SuperDARN, but the outputs
depend mostly on the modelling used. Modellers
are seeking to understand the response of the
neutral atmosphere to, for example, a substorm
and have found the response to storms varies
with time of day, among other parameters.
The satellite map of the aurora is complex,
but in periods when there are abundant SuperDARN data it is possible to compare the ionospheric response with the model, in terms of,
for example, differential heating patterns and
wind responses. Overall, climate models overestimate neutral winds and underestimate the
power going into the upper atmosphere. We can
produce much more realistic models using the
SuperDARN 2-minute data, but there are problems getting the convection models to match
the precipitation data. Progress needs a dense
network of magnetometer and radar stations
across Canada and Norway.
In the US there is nowcasting based on ionospheric data from GPS stations in the northern
US and Europe. We do not know how this feeds
into the ionosphere or into the neutral atmosphere; for example, the lack of knowledge of
the neutral winds in the upper atmosphere hampers understanding of the whole upper atmosphere. Aylward finished by noting that weather
forecasting succeeds because of extensive observational inputs; space weather needs the same.
Mike Lockwood (Reading) then focused on
the solar cycle, beginning by noting that predictions about the future are always tricky. The
record of sunspot data is troubled by noise and
it is not possible to predict the sunspot number
from one cycle to the next using just an autocorrelation function. However, including other
data may make predictions feasible.
Galactic cosmic rays are shielded by the atmosphere, the Earth’s magnetic field and the heliosphere field, i.e. the open solar flux. Present day
mapping of the solar flux is made possible by
data from the Ulysses spacecraft; tracking past
solar activity uses as proxy data cosmogenic
isotopes such as carbon 14 and beryllium 10,
which are formed by spallation from cosmic
rays and leave records trapped in organic matter
and ice sheets respectively. Direct measurements
show that there has been a solar grand maximum from 1955 to 1987; the long-term record
correlates well with recent data and shows that
over the past 8000 years grand maxima are
rare. Most of the time, solar activity is lower.
Overall, Lockwood described the Sun’s behaviour as difficult to explain at present. Currently,
the Sun has a north–south asymmetry and it
appears that the northern hemisphere is carrying on with cycle 24 and the southern hemisphere is not. This has not been seen before
(from 1870 on), suggesting that there is something odd happening. Predictions of the solar
A&G • February 2014 • Vol. 55
Bowler, Livermore: Meeting report
Questions for the future
Who funds space-weather research?
Both Bill Eason (NERC) and Richard
Holme (University of Liverpool) discussed
funding of space-weather related research,
acknowledging that funding now lies largely
within the NERC remit. Through the
NCEO, NERC handles directed funding for
Earth observation and some research on the
geomagnetic field. STFC continues to fund
space-based work such as SEREN.
Where should we put the money?
We have to ask if it is cost-effective to monitor
and counteract the effects on transformers,
for example? There are measures that
could be taken, such as hardening the
infrastructure, turning off transformers when
at risk and improving designs, but all of these
need information about the effects of events
and some predictive capability. Stakeholders
such as business, government and industry
flux suggest fewer but potentially more extreme
space-weather events for the future.
Richard Horne (BAS) spoke about forecasting of radiation belt levels by a project called
SPACECAST, funded by the European Union
Framework 7. Elevated levels of energetic particles in the radiation belts damage satellites by
affecting solar cells, computer memory corruption, surface charging from high-energy (keV)
electrons and deep dielectric charging. There
are examples of the total loss of satellites such
as Telstar 401 (1997) and Galaxy IV (1998), and
satellites such as Galaxy 15 which spent eight
months drifting in geostationary orbit, with
potentially catastrophic consequences. For
example, the 2003 Halloween storm brought
the radiation belts much closer to Earth for a
few days and when they returned to their usual
levels, they were at high intensity. Over this
period, 47 satellites reported anomalies. While
it is difficult to say if space weather is the cause,
it is also difficult to rule it out.
SPACECAST collects data from several sources
and computes the modelled electron flux, allowing not only a comparison between the model
and the US GOES weather satellite data, but
also producing a three-hour forecast. However,
not all the physics is captured accurately in the
model, and indeed some of the data are affected
by the solar wind. The match with GOES data
is reasonable, and although the models miss big
changes in flux, especially losses, they are useful
for determining averages and extremes and for
predicting the next few hours.
SPACECAST is in the process of producing a
real-time forecast for key stakeholders. There
is already a forecast online at all times designed
A&G • February 2014 • Vol. 55 want nowcasts and forecasts. Forecasts rely
on spacecraft in suitable positions, able to
identify solar events on their way to Earth,
but there remain questions about forecasting
the effects of a given class or type of event.
Fundamental physics of the magnetosphere
and its response to solar events is needed to
estimate the geo-response of a space-weather
event before its arrival – valuable information
for vulnerable systems on Earth.
What research would improve spaceweather forecasts?
Data assimilation, the amalgamation of the
physical model and satellite data in order
to produce both nowcasts and forecasts is
probably the best hope. At present, there
is also a lack of suitable data collection
from the upper atmosphere and, despite the
growth in, for example, SuperDARN radar
systems, increased mid-latitude coverage is
for satellite operators, such as the summed electron flux over 24 hours or peak flux, so that they
can take action. Note that insurance companies
require satellite operators to take all reasonable
precautions to protect their technology.
David Johnson (UCL/Met Office) spoke about
the problems associated with data assimilation
in space-weather prediction. This discipline
presents particular problems, in that there is a
lot of information, not uniformly distributed.
Researchers in the field have to find ways to
cope with these very big datasets and manage
the time required to work with them. Development is proceeding based on the coupled middle
atmosphere–thermosphere model, CMAT2.
Ben Taylor (Surrey Space Centre) then spoke
about what satellite engineers need to know.
Radiation is a key issue; it can be difficult to find
specialist radiation-tolerant devices, so manufacturers buy in what they need, then have to
live with uncertain radiation responses. The
result is that satellites are increasingly including more radiation-sensitive devices. Those
building satellites need to know more, and more
detail, about the space environment. Where a
satellite flies makes a difference, for example,
in the specific requirements for its components.
Satellites in low Earth orbit are not exposed to
penetrative radiation but do experience surface
charging, which brings the possibility of differential charging and discharge. Satellites in
geostationary orbits experience sudden plasma
injections from substorms, which can bring
displacement damage from heavier and higher
energy particles, affecting the crystal structure
and performance of semiconductor devices.
Satellites can be protected from these problems
required. Much more work is needed in order
to better understand the magnetosphere and
the effects of the slow changes of the internal
magnetic field (whose dipolar component is
currently weakening). Predictions of solar
activity levels would also be an important
input into any forecast of space climate.
What lessons can we learn?
There are lessons for space weather to be
learned from the experience of scientists
working in climate change. The insurance
industry is currently having to use modelling
rather than experience to work with
the changing climate. For the Sun, past
behaviour is not looking like a good guide
to the future and recent decades have not
been typical, so perhaps there will be a heavy
reliance on model predictions. Researchers
and industry need to use the underlying
science in models more effectively.
by shielding or by switching off components,
because the lower the electric field overall, the
less damage ensues.
Single-event effects such as single particle
strikes from cosmic rays can disrupt devices in
ways that can be recovered, for example by the
traditional “switch it off and on again” method.
However, complex technological devices are
much more susceptible to this sort of damage.
Single events can also produce hard errors – a
permanent change for part of a device. The
problem is bigger for smaller devices.
A further factor is that satellite design takes
place years ahead of the time when the satellites
will be working. Designers would like concise,
useful predictions for the next 10 years or so.
Summary
The meeting finished with group discussions
focused on questions for the future (summarized in the box “Questions for the future”). It
was clear from the presentations and discussion
through the day that there are clear areas for
researchers to address, in order for researchers
in these fields to work together to solve problems that have the potential to affect society
very widely. The consensus of the meeting was
that we could do better for industry and, while
improvements are coming, notably through the
integration into Met Office networks, there is
at present a gap between the data needed and
available, a gap in scientific understanding and
a gap in provision of the science. ●
Phil Livermore ([email protected]) is a
NERC Advanced Research Fellow in the School of
Earth and Environment at the University of Leeds.
1.25