THE IMPACT OF SPACE WEATHER

Modern technological society is characterized by a complex interweave of dependencies and interdependencies among its critical infrastructures. A complete picture of the socioeconomic impact of severe space weather must include both direct, industry-specific effects (such as power outages and spacecraft anomalies) and the collateral effects of space-weather-driven technology failures on dependent infrastructures and services.

Industry-Specific Space Weather Impacts

The electric power, spacecraft, and aviation industries are the main industries whose operations can be adversely affected by severe space weather. The effects of space weather can also be experienced by the growing number of users of the Global Positioning System (GPS) such as the oil and gas industry, which relies on GPS positioning data to support offshore drilling operations.

Electric Power Industry

During intense geomagnetic storms, the auroral oval moves to lower, more densely populated latitudes, where rapidly varying ionospheric currents associated with the aurora can produce direct-current flows in the electrical power grid. Such geomagnetically induced currents (GICs) can overload the grid, causing severe voltage regulation problems and, potentially, widespread power outages. Moreover, GICs can cause intense internal heating in extra-high-voltage (EHV) transformers, putting them at risk of failure or even permanent damage.

The March 1989 Quebec blackout referred to above remains the classic example of the impact of a severe space weather event—the most intense storm of the space age1—on the electric power industry. Storm-related GICs caused a voltage depression in the Hydro-Québec grid that Hydro-Québec’s automatic voltage compensation equipment could not mitigate, resulting in a precipitous voltage collapse over a wide area. Specifically, five transmission lines from the James Bay hydroelectric power generation stations were tripped, causing a generation loss of 9,450 MW. With a load of about 21,350 MW, the system was unable to withstand the loss and collapsed within a minute and a half, blacking out the province of Quebec for approximately 9 hours. The effects of the storm were felt in the United States as well, in the Northeast, the upper-Midwest, the mid-Atlantic region, and even as far south as southern California. Approximately 200 storm-related events were reported to have affected power systems in North America; of these events the most severe was the failure of a large step-up transformer at the Salem Nuclear Power Plant in New Jersey. Other events ranged from generators tripping out of service, to voltage swings at major substations, to other, lesser equipment failures.

Following the 1989 collapse of the Hydro-Québec grid, electric power companies developed operational procedures to protect power grids against disruption and damage by severe space weather. Grid operators receive space weather forecasts from the Space Weather Prediction Center (SWPC) of the National Oceanic and Atmospheric Administration (NOAA) and from commercial and other space weather services. They also monitor voltages and ground currents in real time. During the geomagnetic storms of October and November 2003, for example, power grid opera-



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 EXTENDED SUMMARY THE IMPACT OF SPACE WEATHER Modern technological society is characterized by a complex interweave of dependencies and interdependencies among its critical infrastructures. A complete picture of the socioeconomic impact of severe space weather must include both direct, industry-specific effects (such as power outages and spacecraft anomalies) and the collateral effects of space-weather-driven technology failures on dependent infrastructures and services. Industry-Specific Space Weather Impacts The electric power, spacecraft, and aviation industries are the main industries whose opera- tions can be adversely affected by severe space weather. The effects of space weather can also be experienced by the growing number of users of the Global Positioning System (GPS) such as the oil and gas industry, which relies on GPS positioning data to support offshore drilling operations. Electric Power Industry During intense geomagnetic storms, the auroral oval moves to lower, more densely populated latitudes, where rapidly varying ionospheric currents associated with the aurora can produce direct-current flows in the electrical power grid. Such geomagnetically induced currents (GICs) can overload the grid, causing severe voltage regulation problems and, potentially, widespread power outages. Moreover, GICs can cause intense internal heating in extra-high-voltage (EhV) transformers, putting them at risk of failure or even permanent damage. The March 1989 Quebec blackout referred to above remains the classic example of the impact of a severe space weather event—the most intense storm of the space age1—on the electric power industry. Storm-related GICs caused a voltage depression in the hydro-Québec grid that hydro-Québec’s automatic voltage compensation equipment could not mitigate, resulting in a precipitous voltage collapse over a wide area. Specifically, five transmission lines from the James Bay hydroelectric power generation stations were tripped, causing a generation loss of 9,450 MW. With a load of about 21,350 MW, the system was unable to withstand the loss and collapsed within a minute and a half, blacking out the province of Quebec for approximately 9 hours. The effects of the storm were felt in the United States as well, in the Northeast, the upper-Midwest, the mid-Atlantic region, and even as far south as southern California. Approximately 200 storm- related events were reported to have affected power systems in North America; of these events the most severe was the failure of a large step-up transformer at the Salem Nuclear Power Plant in New Jersey. Other events ranged from generators tripping out of service, to voltage swings at major substations, to other, lesser equipment failures. Following the 1989 collapse of the hydro-Québec grid, electric power companies developed operational procedures to protect power grids against disruption and damage by severe space weather. Grid operators receive space weather forecasts from the Space Weather Prediction Center (SWPC) of the National Oceanic and Atmospheric Administration (NOAA) and from commercial and other space weather services. They also monitor voltages and ground currents in real time. During the geomagnetic storms of October and November 2003, for example, power grid opera-

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 EXTENDED SUMMARY tors in New England responded to severe space weather alerts and to real-time data from GIC monitors by modifying power grid operations in order to maintain adequate power quality for customers and reserve capacity to counteract the effects of the storms. Despite severe GICs, the power transmission equipment was protected, and the grid maintained continuous operation. Spacecraft Operations In late October 2003, powerful solar flares and fast Earthward-directed coronal mass ejections (CMEs) originating in an unusually large sunspot region (see p. 2) triggered especially intense geo- magnetic and radiation storms during which more than half the spacecraft anomalies reported for that year occurred (Figure 1). The impact of space weather on spacecraft systems is not limited to dramatic CME-driven space weather events such as the 2003 “halloween” storms and the March 1989 storm. Of major concern to the spacecraft industry are the periodic enhancements of the magnetospheric energetic electron environment associated with high-speed solar wind streams emanating from coronal holes during the declining phase of the solar cycle as well the injection of energetic plasma into the inner magnetosphere during magnetic substorms, which can occur during nonstorm times as well as storm times. The effect of space weather on spacecraft operations is illustrated by the outage in January 1994 of two Canadian telecommunications satellites in geostationary orbit.2 On January 20, 1994, Telesat’s Anik E1 was disabled for about 7 hours as a result of damage to its control electronics by the discharge of electric charge deposited in the interior of the spacecraft by penetrating high- energy electrons. The outage occurred during an energetic electron storm that had begun a week earlier as a high-speed solar wind stream swept past Earth. During the E1 outage, the Canadian press was unable to deliver news to 100 newspapers and 450 radio stations. In addition, tele- phone service to 40 communities was interrupted. Shortly after E1 was restored to service, its sister satellite, Anik E2, went off the air, resulting in the loss of television and data services to more than 1,600 remote communities. Backup systems were also damaged, making the $290 million satellite useless. Approximately 100,000 home satellite dish owners were required to re-point their dishes manually to E1 and other satellites. It took Telesat operators 6 months to restore Anik E2 to service. The E2 failure is estimated to have cost Telesat $50 million to $70 million (U.S. dollars) in recovery costs and lost business. The principal cause of space-weather-related spacecraft anomalies and failures is radiation in the form of solar energetic particles, galactic cosmic rays, and energetic particles trapped within Earth’s radiation belts or accelerated during magnetospheric substorms. In order to design spacecraft that can withstand the effects of continuous exposure to space radiation and operate 24/7 for 10 to 15 years, spacecraft designers need accurate long-term models of the radiation environment and information about the statistical distribution of extreme events (e.g., the space weather equivalent of the “100-year storm”). Designers are thus concerned primarily with space climatology rather than with specific space weather events. Spacecraft operators, however, require real-time knowledge of the space environment as well as short-term forecasts (“nowcasts”) in order to make operational decisions (e.g., with respect to thruster firing to reposition a spacecraft) that can reduce risks to spacecraft during disturbed conditions. (Such information is also used to support launch go/no-go decisions.) In the event of a spacecraft anomaly, knowledge of the

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 EXTENDED SUMMARY 70 Average # of events/yr = 24.3 Average # of failures/yr = 2.5 60 Most events/failures are not attributed to space weather, but 46 of 70 in 2003 occurred during Halloween storms 50 Number of Reports 40 30 Ave Events 20 Events SC Failures 10 Ave Failures 0 1993* 1994* 1995* 1996* 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 Figure 1. Telecommunication satellite anomalies and failures over a 14-year period. (Data for the years 1993-1996 2.9 Bodeau.eps are less extensive than for the period from 1997 on). The annual probability of an anomaly is around 10 percent, and the annual probability of a failure is about 1 percent. The big spike in 2003 reflects the anomalies that oc- curred during the October-November 2003 “Halloween” storms, which did not produce a significant rise in satellite failures. Around 250 commercial telecommunications satellites are operating in geosynchronous orbit. At a cost of roughly $300 million each, this fleet represents a $75 billion investment and generates an estimated annual revenue stream of more than $250 billion ($100 million per satellite per year). (Image courtesy of Michael Bodeau, Northrop Grumman.) environment where the anomaly occurred as well as climatological information helps operators determine whether or not the anomaly was caused by space weather. Airline Operations In the late 1990s, airline companies began to fly polar routes between North America and Asia in order to avoid strong wintertime headwinds and thus to reduce travel time (Figure 2). Decreased travel time makes it possible to carry less fuel, thus saving costs, and allows the air- lines to transport more passengers and cargo, increasing revenues. Because of the clear economic benefits, the use of polar routes has grown dramatically over the last decade. In 2007, thirteen carriers flew polar routes for a combined total of almost 7300 polar flights, an increase of nearly 2000 flights from the prior year. The transpolar routes take aircraft to latitudes where satellite communication cannot be used, and flight crews must rely instead on high-frequency (hF) radio to maintain communication

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 EXTENDED SUMMARY WASHINGTON 82 N CHICAGO ABERI DEVID RAMEL NIKIN ORVIT BEIJING SHANGHAI HONG KONG Figure 2. Routes flown by transpolar flights between North America and Asia. Originally designated Polar 1, 2, 3, and 4, the routes were re-named after the waypoints ABERI, DEVID, RAMEL, and ORVIT. A fifth route, NIKIN 5.1 Stills.eps (shown in red), was added in 2007. At latitudes above 82° (yellow & typeflight crews cannot use satellite commu- bitmap w vector rules circle), nications and must rely instead on high-frequency (HF) radio to remain in contact with air traffic control. Changes in the polar ionosphere caused by solar energetic particle precipitation can degrade or totally black out HF radio communication. Transpolar flights must therefore be re-routed during intense solar radiation storms (solar energetic particle events). Timely space weather forecasts are important both for short-term (3-4 hour) operational planning and for longer-term (1 day) infrastructure planning (e.g., regarding air crew and aircraft assignments). (Image cour- tesy of Michael Stills, United Airlines.) with the airline company and air traffic control, as required by federal regulation. During certain severe space weather events (referred to by the SWPC as “solar radiation storms”), solar energetic particles—primarily protons accelerated by CME-driven shocks—spiral down geomagnetic field lines into the polar ionosphere, where they increase the density of the ionized gas, which in turn affects the ability of the radio waves to propagate and can result in a complete radio blackout. Such polar cap absorption (PCA) events can last for several days, during which time aircraft must be diverted to latitudes where satellite communication links can be used. During several days of

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 EXTENDED SUMMARY disturbed space weather in January 2005, for example, 26 United Airlines flights were diverted to nonpolar or less-than-optimum polar routes to avoid the risk of hF radio blackouts during PCA events. The increased flight time and extra landings and take-offs required by such route changes increased fuel consumption and raised cost, while the delays disrupted connections to other flights. Space-Based Positioning, Navigation, and Timing The 24 Global Positioning System satellites operated by the United States Air Force provide accurate positioning and timing information to a variety of military, government, and civilian users. In addition, “augmentations” by both commercial services and government agencies improve the accuracy, integrity, and availability of GPS data. For example, as part of the transi- tion to space-based navigation as the primary means of navigation used by the National Airspace System, the Federal Aviation Administration (FAA) has implemented the Wide Area Augmentation System (WAAS), which provides precision horizontal and vertical navigation service over the continental United States, Alaska, and most of Canada and Mexico. WAAS effectively increases the capacity of the aviation system by allowing for reduced horizontal and vertical separation standards between planes without additional risk and by providing highly accurate vertical posi- tioning that enables precision approaches and landings. Current GPS-based navigation and positioning systems are vulnerable to space weather— specifically, to ionospheric density irregularities that affect the propagation of the signals from the GPS satellites to the receivers on the ground. Such irregularities are a routine occurrence near the equator; during magnetic storms, however, they occur in the midlatitude ionosphere as well. Degradation of the GPS signal by ionospheric irregularities produces ranging errors and can result in the temporary loss of GPS reception. Solar radio bursts have recently been found to be an additional source of interference with GPS reception in Earth’s sunlit hemisphere. Systems that use single-frequency receivers without augmentation are vulnerable even to minor ionospheric disturbances. Augmented systems are less susceptible to disruption by minor and moderate ionospheric disturbances but still can be adversely affected by scintillation, solar radio bursts, and major ionospheric disturbances. Thus, when WAAS detects ionospheric distur- bances, it disables the use of precision navigation in the affected areas so that safety is never compromised. When large areas of disturbance are detected, precision navigation is disabled for all areas until 8 hours after disturbances cease. During the October 2003 magnetic storms, for example, WAAS vertical navigation service was disabled for approximately 30 hours, although horizontal navigation guidance was continuously available (Figures 3 and 4). To mitigate the effects of space weather on the GPS, new signals and codes are being imple- mented that will allow GPS receivers to remove ionospheric ranging errors. This capability is expected to make augmentation systems unnecessary. In addition, the new signals and codes will be more resistant to fades caused by scintillation or solar radio bursts. The implementation of the new codes and signals, including the L5 signal dedicated to aviation, will take place incre- mentally over the next decade.

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 EXTENDED SUMMARY Figure 3. Availability of the Wide Area Augmentation System (WAAS) vertical navigation service during a geomag- netically quiet period. Vertical navigation for precision approaches (LPV) is available when the vertical protection level (VPL) is less than or equal to 50 meters;Eldredge COLOR.eps 2.7 for WAAS-enabled approaches with a decision altitude down to 200 feet (LPV200) the VPL must be less than or equal to 35 meters. (LPV, localizer performance with vertical guidance; bitmap LNAV/VNAV, lateral and vertical navigation.) For LNAV/VNAV approaches the VPL must also be less than or equal to 50 meters. The horizonal protection level for LPV and LPV200 approaches—not shown—is 40 meters; for LNAV/ VNAV it is 556 meters. (Image courtesy of Leo Eldredge, Federal Aviation Administration.) In addition to its use in aviation, GPS positioning and timing information is widely used in a number of other applications, including precision farming, surveying and mapping, marine navigation, offshore drilling rig positioning, and transportation. Future Vulnerabilities: The Specter of Extreme Space Weather Past With increasing awareness and understanding of space weather and its effects on modern technological systems, vulnerable industries have adopted procedures and technologies designed to mitigate the impacts of space weather on their operations and customers. As noted above, airlines re-route flights scheduled for polar routes during intense solar energetic particle events in order to preserve reliable communications. Alerted to an impending geomagnetic storm and monitoring ground currents in real-time, power grid operators take defensive measures to protect the grid against GICs. Similarly, under adverse space weather conditions, launch personnel may

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10 EXTENDED SUMMARY Figure 4. Progressive loss of vertical navigation service over North America (top row) as the ionospheric density disturbance (bottom row) worsens during the geomagnetic storm of October 29, 2003. Vertical navigation service over the continental U.S. was not fully restored until around 9:00 a.m. the following day. The color scale in the top panels shows the vertical protection level (VPL) measured in meters; the color scale in the bottom panels shows the vertical ionospheric density in meters. (Image adapted from material supplied by Leo Eldredge, Federal Avia- tion Adminstration.) delay a launch, and satellite operators may postpone certain operations. For the spacecraft indus- try, however, the primary approach to mitigating space weather effects remains designing satellites to operate under extreme environmental conditions to the maximum extent possible within cost and resource constraints. GPS modernization through the addition of the new navigation signals and new codes will help mitigate space weather effects, although to what degree is not known. The FAA will therefore maintain “legacy” non-GPS-based navigation systems as a backup. Our understanding of the vulnerabilities of modern technologies to severe space weather and the protective measures that have been developed are based largely on lessons learned during the past 20 or 30 years, during such episodes of severe space weather as the geomagnetic storms of March 1989 and October-November 2003. As severe as these recent events have been, the historical record reveals that space weather of even greater severity has occurred in the past (e.g., the “Carrington Event” of 1859 and the great magnetic storm of May 1921) and suggests that such extreme events, although rare, are likely to occur again some time in the future (see “The Great Magnetic Storms of August-September 1859,” pp. 14-15).

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11 EXTENDED SUMMARY It is not known how a severe space weather event far more intense than any experienced during the space age might impact our modern technological systems. Of particular concern is the degree to which the electric power grid, which lies at the heart of our national infrastructure, might be affected by such an event. A study by the Metatech Corporation suggests that, despite the protective procedures developed since the hydro-Québec collapse, an unusually powerful magnetic storm could result in widespread outages and possible long-term damage to the nation’s power grid. The Metatech study uses the great magnetic storm of May 1921 (“one of the great- est storms of the past ~130 years”3) to estimate the impact of an extreme space weather event on today’s electric power grid. Using the rate of change in Earth’s magnetic field measured in nanoteslas (nT) per minute as a proxy for GIC intensity, Metatech estimates that GICs during the 1921 storm would have been ten times more intense than those responsible for the March 1989 event. A storm of this magnitude today could result in large-scale blackouts affecting more than 130 million people (Figure 5). Moreover, according to the Metatech analysis, the intense GIC flows produced by the storm would place more than 300 large extra-high-voltage transformers at risk of failure or permanent damage, likely requiring a prolonged recovery period with long-term shortages of electric power to the affected areas (Figure 6). Collateral Impacts of Severe Space Weather An assessment of the societal and economic impacts of severe space weather must look beyond such direct space weather effects as spacecraft anomalies and power grid outages and consider how disruptions of vulnerable technological systems can affect the various sectors of society that are dependent on the functioning of these systems. Given the state of technology in the mid-19th century, the societal and economic impacts of the 1859 Carrington Event were limited to the disruptions of telegraph service “at the busy season when the telegraph is more than usually required,”4 the telegraph companies’ associated loss of income, and whatever the attendant effects on commerce might have been. Should an event of the magnitude of the Car- rington Event occur today, the story could be quite different because of the central role that technology—in particular, electric power—plays in our society and because of the dependencies and interdependencies that characterize our critical infrastructures, rendering them vulnerable to failures cascading from one system to another. Some of the indirect or collateral effects of a severe space weather event are vividly described in the following account of the 1989 hydro-Québec blackout as it was experienced by the citi- zens of Montreal. The blackout closed schools and businesses, kept the Montreal Metro shut down during the morning rush hour, and paralyzed Dorval Airport, delaying flights. Without their navigation radar, no flight could land or take off until power had been restored. People ate their cold breakfast in the dark and left for work. They soon found themselves stuck in traffic that attempted to navigate darkened intersections without any streetlights or traffic control systems operating. . . . All these buildings [in downtown Montreal] were now pitch dark, stranding workers in offices, stairwells, and elevators. By some accounts, the blackout cost businesses tens of millions of dollars as it stalled production, idled workers, and spoiled products.5

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1 EXTENDED SUMMARY Figure 5. Regions susceptible to power grid collapse during a 4800 nT/min geomagnetic field disturbance at 50° 7.1 and C.3a Kappenman.eps geomagnetic latitude, where the densest part of the U.S. power grid lies. The affected regions are outlined in black. Analysis of such an event indicates that widespread blackouts could occur, involving more 130 million people. A disturbance of such magnitude, although rare, is not unprecedented: analysis of the May 1921 storm shows that disturbance levels of ~5000 nT/min were reached during that storm. (Image courtesy of John Kappenman, Metatech Corporation.) � � � � � � � �� �� � � 97% 40%� � � 30% � �� 39% � 7% �� 24% � � � � � � � � � 23% � � � � � � � 72% 34% � 32% � 47% �� �� � �� �� 36%� � 33% 12% � � � �� � � � � � �� � � �� �� � �� � � � � � �� � 26% �� �� � � � � � �� � � � � �� � �� 35% � �� � � �� � � 55% � � �� � 9% � � � � ��� � � �� � � 11% � � ��� � �� � � � � � � ���� � 15% � � � 6% � 82% � � � �� � ��� 24% 19% 18% � � � � �� � � � �� � �� � � � � � � � � �� 19% 55% �� � � 30% � �� � � � � �� � 7% � 47% � 27% � � � � � � � � � � � � �� �� � 17% � �� � �� � � � 17% � � �� � � � � �� � �� 37% �� � �� � � � � � � 38% � 6%� � � 7% � � � 75% 1% �� � � 21% 8% � � � 7.2 and C.3b Kappenman.eps Figure 6. A map showing the extra-high-voltage transformer capacity (estimated at ~365 large transformers), by state, at risk of damage during a 4800 nT/min disturbance. Regions with high percentages could experience long- duration power outages lasting several years. (Image courtesy of John Kappenman, Metatech Corporation.)

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1 EXTENDED SUMMARY A major power blackout, whether the result of severe space weather or severe terrestrial weather, has the potential to affect virtually all sectors of society: communications, transporta- tion, banking and finance, commerce, manufacturing, energy, government, education, health care, public safety, emergency services, the food and water supply, and sanitation (Figure 7). The severity of the impacts depends on a number of variables, including the duration of the outage. The socioeconomic impacts of a long-term outage, requiring replacement of permanently dam- aged transformers, could be extensive and serious. According to an estimate by the Metatech Corporation, the total cost of a long-term, wide-area blackout caused by an extreme space weather event could be as much as $1 trillion to $2 trillion during the first year, with full recovery requir- ing 4 to 10 years depending on the extent of the damage. (For comparison, the total cost for the United States of the August 2003 blackout—a major non-space-weather-related blackout that affected 50 million people in the northeastern United States and Ontario—is estimated to have been between $4 billion and $10 billion.6) Figure 7. Schematic illustrating the interconnection of critical infrastructures and their dependencies and interde- 3.1 Caverly.eps pendencies. As the nation’s infrastructures and services increase in complexity and interdependence over time, a bitmap major outage of any one infrastructure will have an increasingly widespread impact. (Image courtesy of Department of Homeland Security.)

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1 EXTENDED SUMMARY The Great Magnetic Storms of August-September 1859 (the Carrington Event)7 Shortly after midnight on September 2, 1859, campers in the Rocky Mountains were awakened by an “auroral light, so bright that one could easily read common print.” The campers’ account, published in the Rocky Mountain News, continues, “Some of the party insisted that it was daylight and began the preparation of breakfast.” Eighteen hundred miles to the east, Henry C. Perkins, a respected physician in Newburyport, Massachusetts, observed “a perfect dome of alternate red and green streamers” over New England. To the citizens of Havana, Cuba, the sky that night “appeared stained with blood and in a state of general confla- gration.” Dramatic auroral displays had been seen five nights before as well, on the night of August 28/29, when (again in the words of Dr. Perkins) “the whole celestial vault was glowing with streamers, crimson, yellow, and white, gathered into waving brilliant folds.” In New York City, thousands gathered on sidewalks and rooftops to watch “the heavens . . . arrayed in a drapery more gorgeous than they have been for years.” The aurora that New Yorkers witnessed that Sunday night, the New York Times assured its readers, “will be referred to hereafter among the events which occur but once or twice in a lifetime.”8 Low-latitude red auroras, such as those widely reported to have been observed during the Carrington Event, are a characteristic feature of major geomagnetic storms. The aurora shown here was photographed over Napa Valley, Cali- fornia, during the magnetic storm of November 5, 2001. (Image courtesy D. Obudzinski, © Dirk Obudzinski 2001, www. borealis2000.com.)

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1 EXTENDED SUMMARY From August 28 through September 4, auroral displays of extraordinary brilliance were observed throughout North and South America, Europe, Asia, and Australia, and were seen as far south as Hawaii, the Caribbean, and Central America in the Northern Hemisphere and in the Southern Hemisphere as far north as Santiago, Chile. Even after daybreak, when the aurora was no longer visible, its presence contin- ued to be felt through the effect of the auroral currents. Magnetic observatories recorded disturbances in Earth’s field so extreme that magnetometer traces were driven off scale, and telegraph networks around the world—the “Victorian Internet”9—experienced major disruptions and outages. “The electricity which attended this beautiful phenomenon took possession of the magnetic wires throughout the country,” the Philadelphia Evening Bulletin reported, “and there were numerous side displays in the telegraph offices where fantastical and unreadable messages came through the instruments, and where the atmospheric fireworks assumed shape and substance in brilliant sparks.”10 In several locations, operators disconnected their systems from the batteries and sent messages using only the current induced by the aurora.11 The auroras were the visible manifestation of two powerful magnetic storms that occurred near the peak of the sunspot cycle. The two storms, which occurred in rapid succession, are referred as the “Carrington Event” in honor of Richard Carrington, a British amateur astronomer. On September 1, the day before the onset of the second storm, Carrington had observed an outburst of “two patches of intensely bright and white light”12 from a large and complex group of sunspots near the center of the Sun’s disk. Although the connection was not understood at the time, Carrington’s observation provided the first evidence that erup- tive activity on the Sun is the ultimate cause of geomagnetic storms. We know today that what Carrington observed was an extraordinarily intense white-light flare that was associated with a powerful, fast-moving coronal mass ejection (CME). The CME and the shock wave that preceded it impacted Earth’s magnetosphere some 17.5 hours after Carrington’s observation, triggering an unusually severe geomagnetic storm. In addition to the low-latitude auroras and intense auroral currents responsible for the telegraph outages, all of the phenomena known today to be characteristic of a major magnetic storm occurred as well, although the mid-19th century lacked the means to detect and measure them, and its most sophisticated technologies were unaffected by them: an increased Earthward flow of magnetospheric plasma, creating or intensifying the ring current; the explosive release of stored magnetic energy in multiple magnetospheric substorms; an increase in the energy content of the radiation belts as well as the possible creation of temporary new belts; and changes in the ionospheric and thermospheric density at midlatitudes. Recent analysis of ice core data indicates that the geomagnetic storm was also ac- companied by a solar energetic particle event four times more intense than the most severe solar energetic particle event of the space age. By this as well as other measures, the Carrington Event ranks as one of the most severe space weather events—and by some measures the most severe—on record.13 Locations of reported auroral observations during the first ~1.5 hours of the September 2, 1859, magnetic 1.2 Green.eps storm (orange dots). (Image courtesy of J.L. Green, NASA.) bitmap

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1 EXTENDED SUMMARY Box 1 Space Weather: Some Institutional Issues Space weather potentially affects large complex technical systems that are vital for economic and social stability and functioning. But managing the effects of severe space weather is not just a technical problem: it is also, importantly, a problem of institutions and of society. A key issue affecting our ability to prevent disruption of large technical systems is the difficulty of developing the appropriate institutions to deal with the problem on a long-term basis. Institutional devel- opment occurs most often under conditions of frequent accidents or errors. When nothing bad appears to happen from one year to another, sustaining preparedness and planning in out-years is extraordinarily challenging. Consequently, space weather is not on the radar screen of many people outside the small technical community and some affected businesses. Dependency creep, risk migration, and new technologies are potential problems for operators of large technical systems. As systems become more complex, and as they grow in size, understanding and over- sight become more difficult. Subsystems and dependencies may evolve that escape the close scrutiny of organization operators. Dependencies allow risk present in one part the other overall system to “migrate” to others, with potentially damaging results. GPS and electric power systems have clearly accelerated dependency creep, and consequent risk migration. New technologies, such as nanoscale components, may not be adequately understood in the context of 11-year solar cycles. One of the most fundamental concerns for operators of large technical systems is the efficiency-vul- nerability tradeoff—that is, the question of how much reserve capacity is available to deal with uncertainty and contingencies. In stable protected environments, systems operate with excess capacity: costs are passed on to users and the society. In competitive-market but benign environments, however, systems operate at close to their efficiency frontiers. Slack resources are consumed, buffers shrink, costs fall, and profits rise. But in competitive-market and “hostile” environments where unexpected developments perturb the system, finely tuned technical systems become brittle and have trouble operating outside relatively narrow parameters. Vulnerability can be the consequence of increased efficiency. “Security externalities” emerge due to interdependencies, lack of knowledge, lack of slack, lack of trust, and lack of ways to overcome coordination problems. Space storms of the magnitude of the Carrington Event are fortunately very rare, and the risk that such an event might cause a long-term catastrophic power grid collapse with major socio- economic disruptions, while real, is low. In the field of risk analysis, such an extreme event is termed a low-frequency/high-consequence (LF/hC) event. In terms of their potential broader, col- lateral impacts, LF/hC events present a unique set of problems for public (and private) institutions and governance, different from the problems raised by conventional, expected, and frequently experienced events. As a consequence, dealing with the collateral impacts of LF/hC events requires different types of budgeting and management capabilities and consequently challenges the basis for conventional policies and risk management strategies, which assume a universe of constant or reliable conditions. Moreover, because systems can quickly become dependent on new technologies in ways that are unknown and unexpected by both developers and users, vulnerabilities in one part of the broader system have a tendency to spread to other parts of the system. Consequently, it is difficult to understand, much less to predict, the consequences of future LF/hC events. Sustaining preparedness and planning for such events in future years is equally difficult (Box 1).