Blowing in the Solar Wind: Sun Spots,
Solar Cycles and Life on Earth
The Sun regularly experiences eruptions that shower space with energetic ions. In
1859, a massive solar event occurred with a magnitude that surpassed that of all other
recorded events, and the Earth was directly in the path of the storm. Hours after the
eruption, sparks began to fly from telegraph wires, fires were ignited by downed
wires, equipment operators felt electrical shocks from their telegraph keys and ticker
tapes burst into flames. A century and a half later, should a similar solar event occur,
more than wires and paper would be at risk.
Anatoly Arsentiev
Irkutsk, Russia
David H. Hathaway
National Aeronautics and Space Administration
(NASA) Marshall Space Flight Center
Huntsville, Alabama, USA
Rodney W. Lessard
Houston, Texas, USA
Oilfield Review Autumn 2013: 25, no. 3.
Copyright © 2013 Schlumberger.
For help in preparation of this article, thanks to
Don Williamson.
1. Cliver EW: “The 1859 Space Weather Event: Then and
Now,” Advances in Space Research 38, no. 2 (2006):
119−129.
2. Boteler DH: “The Super Storms of August/September
1859 and Their Effects on the Telegraph System,”
Advances in Space Research 38, no. 2 (2006): 159−172.
3. Stephens DL, Townsend LW and Hoff JL: “Interplanetary
Crew Dose Estimates for Worst Case Solar Particle
Events Based on Historical Data for the Carrington Flare
of 1859,” Acta Astronautica 56, no. 9−12 (May−June 2005):
969−974.
48
Those of us in the energy industry owe our livelihoods to the Sun. The hydrocarbons we search for
and produce were formed from organic matter
that stored ancient energy that originated within
the Sun. In the not too distant past, the Sun was
an object of reverence because of its control over
our lives. Today, familiarity with and understanding of the Sun has removed much of our sense of
veneration; however, we understand that our very
existence is based on a relationship to the seemingly unchanging presence of the solar system’s
shining star.
On occasion, however, the Sun’s apparent stability is interrupted by powerful displays of its
dynamism. One such example occurred on the
morning of September 1, 1859. From his private
observatory, amateur astronomer Richard
Carrington observed a cluster of large spots on
the surface of the Sun. Suddenly, a brilliant flash
of white light—a solar flare—erupted from the
area of the spots.1 This particular flare was the
harbinger of a gigantic coronal mass ejection
(CME), which spewed solar plasma into interplanetary space.
This massive cloud of charged particles
arrived at Earth in less than 18 hours. It proceeded to disrupt the most advanced technology
of the day—the telegraph.2 The interaction
between the CME and the Earth’s magnetic field
induced electrical currents in exposed telegraph
wires. Current raced through the wires, causing
some of them to overheat, fall to the ground and
set off fires. Telegraph machines were hit by pow-
erful surges of electricity, which administered
electrical shocks to the operators. Some reports
described telegraph paper bursting into flames
and machines that continued to receive information, even after the operators had disconnected
their battery power. Disturbances in the Earth’s
magnetic field from the effects of the CME caused
compass needles to behave erratically. The
effects were seen not just on the Earth’s surface;
auroras, which are normally restricted to Earth’s
higher latitudes, lit the sky as far south as the
Caribbean region.
Most experts consider the superstorm of
1859, referred to as the Carrington event, to be
the largest recorded solar storm to directly
impact the Earth. Data from ice cores dating
back 500 years show evidence of geomagnetic
storms of varying intensity, but none reached the
magnitude of that singular episode.3
Modern infrastructure has become dependent
on a multitude of interconnected systems and
devices that are sensitive to electromagnetic and
geomagnetic forces. Scientists are concerned that
another Carrington-type CME directed toward
Earth would wreak havoc, overwhelming electrical power grids and control systems, destroying
telecommunications satellites, disrupting global
positioning systems (GPSs) and plunging whole
continents into darkness and disarray. In 1989, a
much smaller geomagnetic storm caused a blackout that pitched the province of Quebec, Canada,
into darkness and disrupted power in many locations in the Northeast US.
Oilfield Review
Autumn 2013
49
250
Quebec blackout
Carrington event
Sunspot number
200
150
100
50
0
1750
1
2
1770
3
4
1790
5
6
1810
7
8
1830
9
1850
10
11
1870
12
13
1890
Date
14
15
1910
16
1930
17
18
1950
19
20
1970
21
22
1990
23
24
2010
> Sunspot cycles. Scientists have systematically recorded the number of sunspots and numbered the sunspot peaks dating from the 1700s. In several
recent cycles, sunspot counts approached or exceeded 200; the current cycle average count is less than 100.
According to solar scientists, predicting the
next Carrington-class event, or any solar storm, is
practically impossible. When solar flares and
CMEs occur, scientists have found it difficult to
determine whether the Earth lies directly in the
path of these streaming ions. In the past few
years, the ability to issue alerts about potential
damaging solar storms has been improved by the
deployment of satellites strategically positioned
to monitor the Sun’s activity.
Although scientists are not able to forecast
exactly when solar flares and CMEs will occur,
they have discovered a correlation between an
increase in the number of sunspots and the frequency and intensity of solar events. Sunspots
are dark regions on the Sun, and they follow an
11-year cycle. During sunspot cycle minima,
there may be no visible spots; during maxima the
number may be greater than 200. Each cycle is
numbered, dating to 1755, when observers began
to systematically record sunspot activity (above).
The Carrington event occurred at the peak of
Cycle 10. The US National Oceanic and
Atmospheric Administration (NOAA) Space
Weather Prediction Center (SWPC) predicts that
Cycle 24 will peak in 2013.4 The Sun has been
relatively quiet during Cycle 24, but the potential
always exists for the Sun to unleash another
Carrington-like event.
This article discusses the concepts of solar
cycles, solar events, CMEs, space weather, solar
monitoring and the potential effects of solar
storms on modern infrastructure, and it reviews
current warning systems.
50
A Not So Benign Sun
About 5 billion years ago, a cloud of dust and gas
approximately 1.6 trillion km [1 trillion mi] in
diameter coalesced to form our solar system.5 The
source of that cloud is believed to be a mix of primordial gas and material from older stars that
exploded in massive supernovae.6 Gravity collapsed
the cloud in upon itself, and mutual attraction of
the particles accelerated the collapse to form a
dense central core. Rotation of the cloud accelerated with contraction, while centrifugal forces flattened the cloud toward the edges, leaving a bulge
near the center from which the Sun evolved.
As the central core of the Sun continued to collapse, the compression generated heat, which
melted and vaporized the dust. About 10 million
years after the collapse began, the rate of collapse
slowed because the pull of gravity was balanced by
the pressure of hot gases. The rising core temperature initiated nuclear reactions, and the heat and
pressure stripped away electrons, leaving mostly
plasma—a mixture of protons and electrons. The
gravitational pull of the Sun continued to compress the plasma in its core to densities nearly ten
times that of lead and heated the plasma to nearly
16 million °C [29 million °F], at which point fusion
reactions can occur.
In the Sun’s fusion reaction, hydrogen atoms
fuse and form helium. During the reaction, some
of the original mass is converted into heat and
photons. The photons radiate outward, first traveling through the radiative zone and then, after
millions of collisions, arrive at the region near
the surface—the convection zone (next page, top
right). From the convection zone, the photons
eventually leave the Sun. Traveling at the speed
of light, photons cover the 150 million km [93 million mi] between the Earth and Sun in about
eight minutes.
The photons emitted by the Sun cover a broad
band of the electromagnetic spectrum—from
high-energy X-rays to radio waves. The Earth is
constantly bombarded by this energy, but because
the atmosphere shields it from most of the emissions, only a few specific frequencies—mostly
those of ultraviolet light, visible light and radio
waves—reach Earth’s surface.
A self-generated magnetic field is a by-product
of the Sun’s fusion reactor, rotation and constantly moving mass of plasma in the convection
zone. Magnetic field lines are generally aligned
with the axis of rotation of the Sun. The field
exhibits a dipolar nature analogous to that of the
Earth, with its north and south magnetic poles.
However, unlike Earth’s magnetic field, the Sun’s
magnetic field reverses polarity on a regular
basis, coinciding with the midpoint of the 11-year
sunspot cycle peak.
The Sun’s rotating magnetic field also generates a current sheet that extends billions of kilometers from the Sun out into space. When the
magnetic polarity reversal occurs—a process
that started in the summer of 2013 for Cycle 24—
the current sheet becomes highly contorted. The
Earth dips in and out of the current sheet while
orbiting the Sun, potentially creating stormy
space weather conditions.7
Oilfield Review
On the surface of the Sun, magnetic field lines
emerge to form sunspots. Magnetic field lines
may encompass volumes that are quite large—
the planet Jupiter, which is 150,000 km
[90,000 mi] in diameter, could easily fit inside
some of them (below right). Coronal loops also
form at the surface, following the magnetic field
lines. During solar sunspot peaks, the number of
coronal loops increases and magnetic field lines
often become twisted. This twisting stores massive amounts of energy that is eventually released
in the form of solar flares, CMEs and other events.
Space weather is punctuated by bursts of energy
from these magnetic disturbances.
Space Weather
Space weather is defined as the physical conditions in the space environment that have the
potential to affect space-borne or ground-based
technology systems.8 Space weather is greatly
influenced by the energy carried from the Sun
by the solar wind, and it can disturb conditions
immediately around the Earth. Charged particles—mainly protons and electrons—make up
the solar wind. These particles are emitted in all
directions from the Sun. Solar wind speed, density and composition determine associated
effects on the Earth.9 Geomagnetic storms, ionospheric disturbances and aurora emissions are
all manifestations of space weather. Coronal
mass ejections and associated shock waves are
the most violent components of space weather,
and they tend to compress the Earth’s magnetosphere and trigger geomagnetic storms.
Earth’s magnetosphere is a bullet-shaped
bubble that protects the planet’s surface from
harmful radiation. The magnetosphere shields
the Earth from fast-moving ions by deflecting
and concentrating them at the Earth’s north
and south poles. The Van Allen radiation belts
trap charged particles that leak through the
magnetosphere, further protecting Earth’s surface from harmful electromagnetic radiation.
4. “NOAA: Mild Solar Storm Season Predicted,” National
Oceanic and Atmospheric Administration (May 8, 2009),
http://www.noaanews.noaa.gov/stories2009/20090508_
solarstorm.html (accessed September 4, 2013).
5. Friedman H: The Astronomer’s Universe: Stars, Galaxies
and Cosmos. New York City: Ballantine Books, 1991.
6. Naturally occurring heavy elements found on Earth, such
as uranium and plutonium, could have come only from an
extremely violent nuclear reaction such as a supernova.
7. Phillips T: “The Sun’s Magnetic Field Is About to Flip,”
NASA (August 5, 2013), http://www.nasa.gov/content/
goddard/the-suns-magnetic-field-is-about-to-flip
(accessed August 28, 2013).
8. Hanslmeier A: The Sun and Space Weather, 2nd ed.
Dordrecht, The Netherlands: Springer, 2007.
9. Feldman U, Landi E and Schwadron NA: “On the Sources
of Fast and Slow Solar Wind,” Journal of Geophysical
Research 110, no. A7 (July 2005): A07109.1–A07109.12.
Autumn 2013
Convection zone
Radiative zone
Core
Photosphere
Prominence
Sunspots
Flare
Coronal hole
Chromosphere
Corona
> The Sun’s structure. Fusion reactions take place in the Sun’s central core. The pull of gravity
accelerates hydrogen nuclei inward, toward the Sun’s center, where they fuse and form helium;
the reaction releases energy. The energy—in the form of photons and other elementary particle
by-products—rises through the Sun’s radiative and convection zones and then exits from the photosphere.
The corona is the Sun’s outer atmosphere, a layer of plasma surrounding the chromosphere. Features
displayed on the Sun’s surface seen here include a prominence, solar flares, sunspots and a coronal
hole. [Illustration courtesy of the US National Aeronautics and Space Administration (NASA).]
> The Sun’s magnetic field lines. Convoluted magnetic field lines (green) may
extend thousands of kilometers out from the surface of the Sun. (Image
courtesy of the NASA Goddard Space Flight Center Scientific Visualization
Studio.)
51
Interplanetary magnetic field lines
Magnetosheath
Bow shock
Magnetopause
Plasmasphere
Magnetotail
Plasma sheet
Solar wind
Van Allen
radiation belts
> Earth’s magnetosphere. The magnetosphere, the area of space around the Earth created by Earth’s
magnetic field, is a dynamic structure that responds to variations in solar activity and space weather.
Solar wind, which compresses the sunward side of the magnetosphere, determines its shape. A
supersonic shock wave—the bow shock—forms on the sunward side of Earth. Most of the solar wind
particles are slowed at the bow shock and directed around the Earth in the magnetosheath. The solar
wind pulls at the magnetosphere on the Earth’s night side, extending the length of the magnetosphere
up to 1,000 Earth radii, creating what is known as the magnetotail. The outer boundary of Earth’s
confined geomagnetic field is called the magnetopause. Trapped charged particles—the Van Allen
radiation belts, the plasmasphere and the plasma sheet—reside within the magnetosphere. (Adapted
from an image courtesy of Aaron Kaase, NASA Goddard Space Flight Center.)
Penumbra
Penumbra
Umbra
Umbra
> Sunspots. Regions on the Sun that appear darker than the rest of the disk, sunspots are formed by
concentrated magnetic fields that project through the hot gases of the photosphere out to the Sun’s
surface. These magnetic fields create cooler, darker regions called sunspots. The dark center of a
sunspot is called the umbra; the light area around the umbra is the penumbra. Sunspots occur in
groups and frequently in pairs. The two spots in a pair have opposite magnetic polarities.
(Photographs courtesy of NASA.)
52
The region of the magnetosphere away from the
Sun is elongated by the pressure of the solar
wind, and the shape varies with space weather
conditions (left).
Space weather has the potential to catastrophically disrupt the near-Earth environment.
The World Meteorological Organization (WMO),
an agency of the United Nations, established the
Interprogramme Coordination Team on Space
Weather (ICTSW) to address concerns of potential disruptions to life on Earth caused by space
weather.10 Experts from twenty countries and
seven international organizations participate in
the program. In the US, NOAA is responsible for
monitoring terrestrial as well as space weather.
The NOAA SWPC constantly monitors data about
the Sun and forecasts solar and geophysical
events that may impact satellites, navigation systems, power grids, communications networks
and other technology systems.11 Because of the
correlation of increases in sunspot numbers with
solar storms, scientists are on high alert during
solar maxima.
Sunspots
About 2,800 years ago, Chinese astronomers
made the first recorded observation of sunspots.12
The invention of the telescope in the 1600s made
it possible to study and record the ever-changing
face of the Sun more closely. Reliable and systematic records of sunspots date back to the 1700s.
In the mid-1800s, German astronomer Samuel
Heinrich Schwabe first identified a 10-year pattern of the rise and fall of sunspots—the sunspot
cycle. Swiss astronomer Johann Rudolf Wolf later
characterized the 11-year period for the cycle
and developed a formula for quantifying sunspot
activity, the Wolf number, which is still in use
today.13 The cycle is not exactly 11 years but has
varied from 9 to 14 years.
Sunspots form where concentrated magnetic
field lines project through the hot gases of the
photosphere and correspond to regions that are
cooler than the surrounding surface. Although
they appear darker than the rest of the solar disk,
removed from the Sun, they would be brighter
than anything else in the solar system (left). The
importance of the complex magnetic fields to the
activity of the Sun has been realized only within
the past 100 years. American astronomer George
Ellery Hale first reported solar magnetism in
1908. He determined the presence of magnetic
fields by measuring changes to intensity and
polarization of light emitted from atoms in the
Sun’s atmosphere.14 Hale and his colleagues demonstrated that sunspots contain strong magnetic
Oilfield Review
fields and that all the sunspot groups in a given
solar hemisphere have the same magnetic polarity signature. Furthermore, sunspot polarity correlates to the Sun’s magnetic field orientation in
a specific solar cycle, which reverses with each
cycle. The hemisphere that has a north magnetic
polarity at one solar minimum has a south magnetic polarity at the next solar minimum.
Sunspots typically range in size from 2,500 to
50,000 km [1,500 to 30,000 mi] and cover less
than 4% of the Sun’s visible disk. In comparison,
the Earth’s diameter is about 12,700 km
[7,900 mi]. Sunspots typically have a lifetime of a
few days to a few weeks and tend to be concentrated in two midlatitude bands on either side of
the Sun’s equator. During the early part of the
solar cycle, sunspots are most commonly seen
around latitudes of 25° to 30° north and south of
the equator. Later in the cycle, they appear at
latitudes of 5° to 10°. Sunspots rarely occur at
latitudes above 50°.
The intense magnetic fields associated with
sunspots often create arching columns of plasma
called prominences that appear above sunspot
regions (right). Some prominences may hang suspended above the solar surface for several days.
When these massive loops of energy become
twisted, they store energy that can violently erupt
and blast coronal material outward from the Sun
as a solar flare or a CME.
Prominence
> Solar prominence photographed on September 23, 1999. The space-based Solar and Heliospheric
Observatory (SOHO) captured this image of an eruptive prominence using extreme ultraviolet
frequencies. The release of energy from twisted magnetic field lines flings plasma above the Sun’s
surface. [Photograph courtesy of the SOHO Extreme Ultraviolet Imaging Telescope (EIT) consortium.]
Solar Flares and CMEs
The energy source for solar flares originates in
the tearing and reconnecting of magnetic field
lines, and the strong magnetic fields in active
sunspot regions often give rise to solar flares
(right). These intense, short-lived releases of
energy are our solar system’s most explosive
events. During a solar flare, temperatures soar to
5 million °K, and vast quantities of particles and
radiation can be blasted into space, but a flare
usually ends within 20 minutes.
10. For more on WMO and ICTSW: “WMO Scientific and
Technical Programs,” World Meteorological
Organization, http://www.wmo.int/pages/prog/
(accessed August 1, 2013).
11. For more on the SWPC: NOAA National Weather Service
Space Weather Prediction Center, http://www.swpc.
noaa.gov/AboutUs/index.html (accessed August 13, 2013).
12. Clark DH and Stephenson FR: “An Interpretation of the
Pre-Telescopic Sunspot Records from the Orient,”
Quarterly Journal of the Royal Astronomical Society 19,
no. 4 (December 1978): 387−410.
13. Hathaway DH: “The Solar Cycle,” Living Reviews in
Solar Physics 7 (2010): 1–65.
14. Alexander D: The Sun. Santa Barbara, California, USA:
Greenwood Press, 2009.
> Solar flare. The NASA Solar Dynamics Observatory (SDO) captured this image of a solar flare on
May 22, 2013. The image captures light in the 13.1-nm wavelength, which highlights material heated to
intense temperatures during a flare. The teal coloration is typical of images using this wavelength.
(Photograph courtesy of the NASA SDO.)
Autumn 2013
53
> Auroras at high latitudes. Charged particles from solar wind and geomagnetic storms follow the Earth’s magnetic field lines and can ionize gases in Earth’s
upper atmosphere. Ionized oxygen molecules emit green to brownish-red light; ionized nitrogen emissions are blue or red. The aurora borealis (left) was
photographed from the International Space Station over the Midwest US on January 25, 2012. The photograph of the aurora australis (right) captured by the
NASA IMAGE satellite on September 11, 2005, was taken four days after a solar flare. The aurora encircles the South Pole and would appear as a curtain of
light if observed from ground level. (Photographs courtesy of the NASA International Space Station and IMAGE Science Center.)
During the peak of the sunspot cycle, several
flares may occur daily. When a flare erupts, ultraviolet and X-ray radiation from the flare travel at
the speed of light, arriving at the Earth in about
8 minutes. A day or two later, high-energy particles may also arrive at the Earth, producing auroras—lights in the polar night skies—and
affecting radio communications (above).15
Sun’s
diameter
> CME image captured from space on October 22, 2011. The Large Angle and Spectrometric
Coronagraph (LASCO), on board the NASA SOHO satellite, captured this image in which plasma was
hurled in the direction of Mars. The Sun is obscured by a disk that allows the instrument’s sensor to
focus on the emissions from the Sun’s surface, which enhances the observation of the corona by
blocking direct light from the Sun. The white circle on the disk represents the size and location of the
Sun’s surface. (Photograph courtesy of the SOHO EIT consortium.)
54
During some solar flares, a more violent reaction may occur—a coronal mass ejection (below
left). When the twisted magnetic field lines cross,
their stored energy explodes outward with tremendous force. A CME occurs when the force of
the released energy flings a mass of superheated
plasma from the Sun’s surface into space.
CMEs vary in intensity and magnitude. A large
CME can contain 9 × 1012 kg [20 × 1012 lbm] of
matter that may be accelerated into space at several million kilometers per hour. The speed at
which the plasma travels depends on the original
energy release. A high-energy CME can arrive at
the Earth in as little as 16 hours, but lower-energy
releases may take days to make the journey.
Upon impact by a CME, the Earth’s magnetosphere temporarily deforms, and the Earth’s
magnetic field is distorted. During these disruptions, Earth-orbiting satellites are exposed to
ionized particles, compass needles can behave
erratically and electrical currents may be
induced in the Earth itself. These events—geomagnetic storms—can disrupt technical infrastructure on a global scale. Because of the risks
associated with solar storms and CMEs, scientists constantly monitor space weather.
At a solar minimum, the estimated occurrence of a CME is about one event every five days
compared with about 3.5 per day at a solar maximum. Although this may appear to put the planet
in frequent jeopardy, the probability that a CME
will be directed toward Earth is small. In comparison to the Sun and the expanse of the solar
Oilfield Review
L4
Moon
Earth
L3
L1
L2
Sun
L5
> Lagrange points. Scientists have identified five points (L1 through L5) associated with Earth’s orbit of
the Sun where satellites can maintain stable orbits. These locations, called Lagrange points (green),
are shown here with the gravitational potential lines (gray lines) established by the Sun-Earth system.
These positions in space correspond to regions where the gravitational forces of attraction (red
arrows) and repulsion (blue arrows) are in balance. The Wilkinson Microwave Anisotropy Probe
(WMAP) is located around position L2, which is about 1.5 million km [930,000 mi] from the Earth.
The WMAP spacecraft aligns with the Sun-Earth axis, similar to a geostationary orbit, but course
corrections are required to maintain its relative position. The illustration is not to scale. (Illustration
courtesy of the NASA WMAP Science Team.)
system, the Earth is tiny; most solar storms fire
harmlessly away from Earth or deliver only a
glancing blow.
But CMEs do strike the Earth. The Carrington
event is not the only CME that has directly
impacted Earth. In 1984, US President Ronald
Reagan was airborne in the presidential plane
Air Force One over the Pacific Ocean during a
solar storm. The storm disrupted high-frequency
radio communication for several hours and effectively isolated Air Force One from the rest of the
world. In July 1989, a portion of Quebec, Canada,
was blacked out for more than nine hours
because a solar storm overloaded circuit breakers on the power grid. More than 200 related
events were reported across North America. The
US National Academy of Sciences reported that
had the storm been a Carrington-class event, cost
could have ranged from US$ 1 to 2 trillion in damage to critical infrastructure, and recovery could
have taken 4 to 10 years.16
Autumn 2013
Forecasting Space Weather
Technologies that are sensitive to changes in the
near-Earth electromagnetic environment caused
by geomagnetic storms include satellite communication systems, global positioning systems
(GPSs), computer networks, electric grids and
cell phone networks. Civilization has become
increasingly dependent on these technologies,
and space weather has the potential to disrupt
them. Thus the need for accurate space weather
forecasts has become imperative. The NOAA
SWPC serves as the primary warning center for
the US and provides information to the
International Space Environment Service (ISES).
ISES—a collaborative network of space weather
providers—monitors space weather, provides
forecasts and issues alerts from regional warning
centers. Using a wide array of terrestrial and
space-based sensors, scientists continually monitor the space environment for events that might
impact Earth.
About 1.6 million km [1 million mi] from the
Earth, in the general direction of the Sun, a group
of NASA satellites monitors the Sun and solar
wind at the L1 Lagrange point (above).17 In what
is analogous to a geostationary orbit, spacecraft
remain in fixed positions with the Earth’s orbit
relative to the Sun. The Solar and Heliospheric
15. Comins NF and Kaufmann WJ: Discovering the Universe,
9th ed. New York City: W. H. Freeman and Company, 2012.
16. National Research Council of the National Academies:
“Severe Space Weather Events—Understanding
Societal and Economic Impacts: A Workshop Report,”
Washington, DC: National Academies Press, May 2008.
17. The Lagrange points, named for Italian-French
mathematician Joseph-Louis Lagrange, are the five
positions where a small mass can maintain a constant
pattern while orbiting a larger mass. The L1 point lies in
a direct line between the Earth and Sun.
For more on the Lagrange points: “The Lagrange
Points,” National Aeronautics and Space Administration,
http://map.gsfc.nasa.gov/mission/observatory_l2.html
(accessed August 1, 2013).
55
> The NASA Advanced Composition Explorer (ACE). Launched on August 25, 1997, the ACE satellite, a
crucial component of the NASA space weather monitoring fleet, is stationed at Lagrange point L1.
From this position, the satellite records radiation emitted from the Sun, the solar system and the
galaxy. When bursts of solar material stream toward Earth, instruments on board ACE record the
increase in the number of particles and transmit this information to scientists on Earth who use these
data to warn of impending space weather events. Alerts and warnings are issued to relevant
organizations and posted online by the NOAA SWPC. (Illustration courtesy of NASA.)
Relative size
of Earth
> Space weather monitoring by SOHO. The SOHO satellite (right) was launched in December 1995.
SOHO is a joint project between the European Space Administration (ESA) and NASA to study the Sun
from its deep core to the outer corona and the solar wind. The satellite weighs about 17.8 kN [2 tonUS],
and its solar panels extend about 7.6 m [25 ft]. This solar eruption (left), which lasted four hours, was
photographed on December 31, 2012, by the Extreme Ultraviolet Imaging Telescope (EIT) in 30.4-nm
emission. Most of the plasma fell back to the Sun’s surface. The Earth is shown for scale. (Solar
photograph courtesy of the SOHO EIT consortium; satellite image courtesy of Alex Lutkus.)
56
Observatory (SOHO), the Advanced Composition
Explorer (ACE) and other space-bound assets
monitor the Sun’s surface and track CMEs from
this position.18 Hours before a CME impact, satellite sentinels at the L1 point can anticipate its
arrival at the Earth’s magnetosphere (left).
The SOHO satellite, launched in 1995, allows
scientists to constantly monitor the Sun (below
left). This satellite is one of the most reliable
NASA and European Space Agency (ESA) forecasting tools, providing scientists with data to
help them forecast space weather and estimate
potential consequences. The Large Angle and
Spectrometric Coronagraph (LASCO), one of 12
instruments on board SOHO, records images of
CMEs launched from the Sun. Using LASCO data,
the SWPC has two to three days of advanced
warning for the onset of geomagnetic storms.
The Solar Dynamics Observatory (SDO), developed at the NASA Goddard Space Flight Center in
Greenbelt, Maryland, USA, and launched on
February 11, 2010, is part of a five-year NASA mission to study the Sun and its influence on space
weather (next page).19 Several devices are on
board the satellite, including the Extreme
Ultraviolet Variability Experiment and the
Atmospheric Imaging Assembly. The helioseismic
and magnetic imager provides real-time maps of
magnetic fields on the surface of the Sun and measures their strength and orientation. Changes and
realignment of the Sun’s magnetic fields are early
indications of potential eruptions and are crucial
for the prediction of space weather and geomagnetic storms. Instruments on board the satellite
can also characterize the interior of the Sun,
where the magnetic fields originate. From SDO
data, scientists are gaining a better understanding
of solar activity and space weather.
Geomagnetic Storms Brewing
Geomagnetic storms that disrupt activities on
Earth are infrequent, although their consequences are significant; solar storms have the
potential to disturb the entire planet. The technologies that define modern society are susceptible to the effects of space weather. Induced
currents can disrupt and damage modern electrical power grids and cripple satellites and
communication systems. For the oil and gas
industry, geomagnetic storms can adversely
affect pipelines and supervisory control systems
and disrupt surveying and geosteering operations while drilling.
Oilfield Review
Filament
Magnetic field lines
> The Solar Dynamics Observatory (SDO). The SDO satellite (left) was launched in February 2010 as part of the NASA Living with a Star Program, which
studies solar variability and potential impacts on Earth and space. By examining the solar atmosphere on small scales and capturing emissions at many
wavelengths simultaneously, the study hopes to determine how the Sun’s magnetic field is generated and structured and how stored magnetic energy is
converted and released into the heliosphere and space. This image of the Sun’s magnetic field lines (right), captured on June 4, 2013, was taken in extreme
ultraviolet light and highlights the bright coils of magnetic field lines rising up in the background above an active region. A filament, which appears as a
darker region on the Sun’s surface, can also be seen. (Photograph and image courtesy of the NASA SDO.)
The most crippling effects of geomagnetic
storms come from geomagnetically induced currents (GICs) that flow through electrical power
grids. At the most benign level, GICs can trip circuit breakers, but stronger events can destroy
transformers and trigger component meltdown
throughout large geographic areas.
GICs damage transformers by driving them
into half-cycle saturation—the core of the transformer is magnetically saturated on alternate
half cycles. A GIC-induced voltage level of as
little as 1 to 2 volts per kilometer or current of
5 amperes is sufficient to drive transformers into
saturation in one second or less.20 Engineers have
measured GIC currents as high as 184 amperes
during geomagnetic storms; these levels are far
Autumn 2013
above that required to overload electrical grids.21
In the event of a severe GIC incident, the time
required to restore damaged equipment and
bring large populations back online might be
measured in weeks, months or even years.
When the charged plasma cloud of a CME collides with Earth’s atmosphere, transient magnetic waves alter Earth’s normally stable
magnetic field; the effects can last for several
days. These magnetic disturbances may cause
voltage variations along the Earth’s surface,
inducing electrical currents between grounding
points because of the voltage potential differences. GICs in this form are particularly detrimental to transformers typically found in power
plants and electrical distribution substations.
Several factors dictate the susceptibility of a
given electrical power grid system to disruption
and damage from solar storms. A power grid’s
proximity to Earth’s polar latitudes generally
increases its risk for failure or malfunction. In
addition, sites located in regions of low ground
18. For more on SOHO: http://sohowww.nascom.nasa.gov/
(accessed August 13, 2013).
For more on ACE: http://www.srl.caltech.edu/ACE/
(accessed August 13, 2013).
19. For more on SDO: http://sdo.gsfc.nasa.gov/ (accessed
August 13, 2013).
20. For more on detrimental effects on power grids:
Barnes PR, Rizy DT, McConnell BW, Tesche FM and
Taylor ER Jr: “Electric Utility Industry Experience with
Geomagnetic Disturbances,” Oak Ridge, Tennessee,
USA: Oak Ridge National Laboratory, ORNL-6665,
September 1991.
21. Odenwald S: The 23rd Cycle: Learning to Live with a
Stormy Star. New York City: Columbia University
Press, 2001.
57
Typical auroral
zone location
Region
conductivity, S/m
CANADA
1 to 10
10–1 to 1
10–2 to 10–1
10–3 to 10–2
10–4 to 10–3
Auroral zone extreme
on March 13, 1989
UNITED STATES
CANADA
MEXICO
UNITED
STATES
Highest risk
Medium risk
Connected power grids
MEXICO
> Power system susceptibility. Power systems in areas with the lowest ground conductivity (left, red and darkest yellow) are the most vulnerable to the
effects of intense geomagnetic activity. The high ground resistance beneath these areas facilitates the flow of geomagnetically induced currents (GICs) in
power transmission lines. Auroral zones for North America are susceptible to GICs because of their proximity to polar regions. (Data from the American
Geophysical Union and the Geological Survey of Canada.) For the US, scientists produced a map based on scenarios for existing power systems to
determine their vulnerability to geomagnetic storms (right). Should a storm 10 times larger than the 1989 storm that disrupted power systems in Quebec
arrive at Earth, the systems most at risk have been identified (red). The blue lines encircle the largest population centers served by at-risk systems.
(Adapted from the National Research Council of the National Academies, reference 16.)
conductivity, such as igneous rock provinces, are
more susceptible to GIC effects (above).
The interconnectivity of power grids can
exacerbate the potential for large-scale problems. During the July 1989 solar storm, many
related events were reported. These events
included a transformer failure at the Salem
nuclear plant in New Jersey, USA; New York
Power losing 150 MW the moment the Quebec
power grid went down; and the New England
Power Pool, an association of power suppliers,
losing 1,410 MW. Service to 96 electrical utilities
58
in the New England region of the US was interrupted before power companies could bring other
reserves online.22
Damage caused by energized particles emitted from the Sun is not limited to terrestrial systems. Satellites, space exploration vehicles and
manned space missions can be affected by solar
emissions, some of which are too weak to enter
Earth’s magnetic field. For instance, weak solar
flares and CMEs may produce solar proton events
(SPEs) that are mostly unnoticed on the surface
of the Earth. However, SPEs can cause significant
damage to equipment located outside Earth’s
protective shield.
When high-energy charged particles collide
with satellites, electrons create a dielectric
charge within the spacecraft. This static charge
can destroy electronic circuit boards, alter and
scramble stored data and affect control instructions stored in computer memory. Although these
effects may result in a complete satellite failure,
damage may often be corrected by simply rebooting onboard computers.
Oilfield Review
Autumn 2013
264
263
Azimuth, degree
If the solar arrays that provide power to satellites are struck by high-energy protons from SPEs
and CMEs, the silicon atoms in the solar cell
matrix may shift positions, which increases the
internal resistance of the solar cells and reduces
electrical output. A single solar storm event can
decrease panel life expectancy by years. If attitude control systems on satellites used to correct
their orientation and position are damaged by
high-energy particle events, a satellite can lose
its orbital control, which may result in an
unplanned and premature reentry into Earth’s
atmosphere.23 Satellites play such a crucial role
in communications that a loss could affect television, cable programming, radio service, weather
data, cell phone service, automated banking services, commercial airline systems and GPS and
navigation services. Routine losses as a result of
satellite malfunction and premature asset failure
caused by solar storms are estimated in the billions of US dollars.
Consequences of solar storms may not be
limited to electrical damage. The July 1989
solar storm caused compression of the Earth’s
magnetosphere, reducing its typical depth of
more than 54,000 km [33,500 mi] to less than
30,000 km [18,640 mi], well inside the Earth’s
geosynchronous region where satellites orbit.
As the Earth’s atmosphere was bombarded by
energetic particles and compressed by the solar
wind, the density of the upper atmosphere
increased by a factor of 5 to 10. The increased
drag on low-Earth orbit satellites caused orbital
decay—the U.S. Air Force Space Command
reported losing track of more than 1,300 orbiting objects that fell to lower altitudes.24 In a
separate event, on March 13, 1989, NOAA
reported the loss of the GOES-7 weather satellite. Circuit problems caused by a shower of
energized particles rendered most of its systems
useless. Critical solar power arrays on GOES-7
lost 50% of their efficiency. Engineers with
NASA reported many other satellites experienced electrical failures that temporarily shut
down onboard computers.25 The storm disrupted
communications on the Earth and between
ground controllers and orbital satellites.
Oil and gas pipeline and distribution systems
are also vulnerable. In the event of a geomagnetic
storm, operators may immediately lose supervisory control and data acquisition (SCADA) systems. Operators must also consider the long-term
effects associated with increased pipeline corrosion rates. Cathodic protection systems used on
pipelines to minimize corrosion maintain a negative potential with respect to the ground. During
solar storms, GIC events in a pipeline reduce the
Magnetic
storm
262
261
Drilling azimuth
Corrected azimuth
260
259
3,600
3,700
3,800
3,900
4,000
4,100
4,200
Depth, ft
4,300
4,400
4,500
4,600
4,700
> Geomagnetic storms and directional drilling. Directional drillers use MWD tools to determine drillbit
orientation and position; these measurements depend on data derived from magnetometers and
accelerometers. During geomagnetic storms, magnetometers may provide erroneous readings. A solar
storm occurred while an operator drilled a North Sea well, and the MWD drilling azimuth measurement
(blue) was affected by the geomagnetic storm. Engineers corrected the data using a technique
developed by the British Geological Survey that adjusts for space weather. The results provided a more
accurate well location (green). (Adapted from Clark and Clarke, reference 28.)
effectiveness of the cathodic protection, which
may increase long-term corrosive effects.26 The
level of impact is affected by the specifics of pipe
construction materials, pipeline diameter, bends,
branches, insulated flanges and the integrity of
insulation materials.
Operators are also concerned about the large
percentage of modern oil and gas wells that are
drilled directionally. Drillers must use strict well
trajectory plans to control borehole position relative to the reservoir and to avoid collision with
nearby wellbores. Directional drilling relies on
instruments that make real-time measurements
to determine and track the subsurface location of
the drilling assembly. Triaxial magnetometers
measure the strength of the Earth’s magnetic
field, and triaxial accelerometers are used to
correct magnetometer data for position, motion
and orientation. Gyrocompasses—using gyroscopes and the rotation of the Earth to find
geographic north—are also deployed on wireline to acquire precise directional surveys.27
Disturbances in the Earth’s magnetic field arising from electric currents flowing in the ionosphere and the magnetosphere can affect these
measurements (above). Mirror currents may also
be induced in the Earth and oceans by variations
in the Earth’s magnetic field. These external
magnetic fields are affected by the solar wind,
the interplanetary magnetic field and the Earth’s
magnetic core. Well placement engineers must
be acutely aware of geomagnetic disturbances
and variations in Earth’s magnetic field to ensure
proper borehole placement.28 (See “Geomagnetic
Referencing—The Real-Time Compass for
Directional Drillers,” page 32.)
The Earth’s climate is also susceptible to
space weather and to particle emissions from the
Sun. Although the Sun appears to be a constant
energy source, scientists have demonstrated
22. North American Electric Reliability Corporation (NERC):
“Effects of Geomagnetic Disturbances on the Bulk
Power Systems,” Atlanta, Georgia, USA: NERC
(February 2012).
23. Odenwald, reference 21.
24. Alexander, reference 14.
25. Odenwald, reference 21.
26. Zurich Financial Services Group: “Solar Storms:
Potential Impact on Pipelines,” http://www.zurich.com/
internet/main/SiteCollectionDocuments/insight/
solar-storms-impact-on-pipelines.pdf (accessed
September 5, 2013).
27. Ekseth R and Weston J: “Wellbore Positions Obtained
While Drilling by the Most Advanced Magnetic
Surveying Methods May Be Less Accurate than
Predicted,” paper IADC/SPE 128217, presented at the
IADC/SPE Drilling Conference and Exhibition,
New Orleans, February 2–4, 2010.
28. Clark TDG and Clarke E: “2001 Space Weather Services
for the Offshore Drilling Industry,” poster presentation in
Proceedings from the ESA Space Weather Workshop:
Looking Towards a Future European Space Weather
Program. Noordwijk, The Netherlands, December
17–19, 2001.
59
400 Years of Sunspot Observed Data
Sunspot numbers
250
Northern Hemisphere Temperatures over the Last 1,000 Years
Temperature
Medieval warm period
200
Dalton
Minimum
150
100
Modern
maximum
Less-reliable observation data
Reliable observation data
Maunder
Minimum
50
0
1600
1650
1700
1750
1800 1850
Date
1900
1800
1900
1950
2000
Mean temperature
Little Ice Age
900
1000
1100
1200
1300
1400
1500
1600
1700
2000
Date
> Sunspot cycles and terrestrial weather. Scientists have not reached consensus regarding the effects of solar activity on the Earth’s climate and weather.
Most, however, would agree that the Sun is the primary heat source for the Earth, thus the major driver of climate. Some scientists have tried to draw
a correlation between the absence of sunspots during the Maunder Minimum (top)—a 70-year period in the 17th century—and the Little Ice Age that
affected much of the Earth, especially Europe (bottom). The Dalton Minimum, another period of low sunspot occurrences around 1800, corresponded to
lower than average global temperatures, as well. The rise in total average number of sunspots (black) beginning in the 1900s appear to correspond to
increases in global temperatures. Although a close examination of the data points to other factors producing temperature variations, such as volcanic
eruptions and changes in CO2 levels, some observers propose solar activity as a major component in climate and temperature fluctuations. The activity of
Solar Cycle 24 is comparable to that in the cycles around 1800 rather than those of the 20th century. A century from now, scientists may be able to look back
and debunk or validate the causal relationship of sunspots to climate change.
that the base energy output of the Sun varies up
to 0.5% on short timescales and 0.1% over the
11-year sunspot cycle. Considered significant by
atmospheric scientists, these fluctuations can
affect Earth’s climate. Variations in plant growth
have been correlated with the 11-year sunspot
cycle and 22-year magnetic period of the Sun, as
evidenced in tree ring records.29
Although the solar cycle has been relatively
steady during the last 300 years, during a 70-year
period in the 17th century, few sunspots were
observed. This period, referred to as the Maunder
Minimum, also coincided with the timing of the
Little Ice Age in Europe. Some scientists have
theorized that this is evidence of a Sun-Earth climate connection (above).30 Recently, scientists
have proposed a more direct link between the
Earth’s climate and solar variability. For instance,
the stratospheric winds near the Earth’s equator
29. For recent research on solar cycles’ effects on Earth’s
weather: Meehl GA, Arblaster JM, Matthes K, Sassi F
and van Loon H: “Amplifying the Pacific Climate System
Response to a Small 11-Year Solar Cycle Forcing,”
Science 325, no. 5944 (August 2009): 1114−1118.
30. Weng H: “Impacts of Multi-Scale Solar Activity on
Climate. Part I: Atmospheric Circulation Patterns and
Climate Extremes,” Advances in Atmospheric
Sciences 29, no. 4 (July 2012): 867−886.
31. Weng H: “Impacts of Multi-Scale Solar Activity on
Climate. Part II: Dominant Timescales in DecadalCentennial Climate Variability,” Advances in
Atmospheric Sciences 29, no. 4 (July 2012): 887−908.
32. “Solar Storm Warning,” NASA (March 15, 2006),
http://www.nasa.gov/vision/universe/solarsystem/
10mar_stormwarning.html (accessed August 18, 2013).
33. Zurich Financial Services Group, reference 26.
60
change direction with each solar cycle. Studies
are underway to determine how this wind reversal affects global circulation patterns, weather
and climate.31
The Next Big Event
Geomagnetic storms, although infrequent, can
severely impair critical infrastructures of modern
society. Because we are increasingly dependent
on susceptible technologies in our interconnected global economy, solar storms have the
potential to create havoc on a worldwide scale.
The scientific community is working to improve
its understanding of the technical aspects of this
threat and the related vulnerabilities in various
industry segments to better manage risk.
The science of space weather forecasting is
still in its infancy. Scientists cannot accurately
forecast the number of sunspots before the start
of a solar cycle or predict geomagnetic storm
activity, although some organizations do make
attempts. A decade ago, before the start of
Cycle 24, some forecasters were predicting the
most intense solar maximum in 50 years and that
the cycle might result in devastating geomagnetic storms.32 But those forecasts were wrong.
The sunspot activity of Solar Cycle 24 has
been the lowest in more than 100 years, barely
half the activity level of Cycle 23. Some scientists
speculate that the Sun is entering another quiet
period similar to the Maunder Minimum and are
asking questions: Will global climate effects be
similar to those of the Little Ice Age during the
Maunder Minimum or is there no direct correlation between sunspots and terrestrial climate?
Or is this just the quiet before the storm? Even
during a relatively low-amplitude solar cycle, a
CME can be triggered that makes a direct hit on
planet Earth.
The recurrence probability of the 1859
Carrington event is estimated at 1 in 500 years,
and the recurrence probability of the 1989
Quebec storm is estimated at 1 in 150 years.33
Although scientists, engineers and risk managers
are concerned about the potential damage of
another Carrington-type event, they have many
more tools at their disposal to help them predict
and react when such an event occurs. These tools
allow the scientific community to remain vigilant
to the Sun’s activity and be prepared to act.
The list of solar storm consequences grows in
proportion to our dependence on electromagnetically sensitive technology systems. The SWPC
and ISES, working with many national and international partners, continue to develop improved
monitoring and space weather modeling capabilities. Advances in Earth-bound and satellite-based
data acquisition systems, along with modeling
and a better understating of our interlinked relationship with the Sun, hold promise of reducing
our exposure risk when the Earth is directly in
the path of the next great solar storm.
—TS
Oilfield Review