Frequently Asked Questions about the Sun and Earth: Space Weather, Solar Flares, Auroras, and Geomagnetically Induced Current



How Do Solar Storms and Space Weather Affect Earth?

Magnetospheres: The Earth and Sun both have magnetic fields known as magnetospheres. The Sun's magnetosphere is known as the heliosphere and has been key to the development and sustainability of life on Earth as it protects the nearby planets from a variety of intragalactic phenomenon that could potentially devastate life. Similarly, the Earth's magnetosphere somewhat shields it from normal emissions from the Sun: Auroras are frequently the result of a "solar wind" or ejected particles buffeting the earth and interacting with our magnetosphere. Occasionally, the Sun's magnetic field developes distortions or "tangles," which can result in sunspots, solar flares, and coronal mass ejections (NASA, 2010)

An artist's rendition of solar emissions hitting the Earth's magnetosphere. Above and right Images by NASA.

Sunspots are slightly cooler regions of the sun's corona, or outer layer, which can sometimes be observed from the Earth with a solar telescope or, at times, the naked eye.

Solar flares are associated with sunspots, and are sudden bursts of radiation that occur with some regularity on the Sun as a result of naturally occurring magnetic fluctuations on the Sun. They include radiation all across the electromagnetic spectrum, from visible light to gamma rays. The patterns of sunspots and solar flares have been directly recorded since around 1749, which has shown that periods of heightened solar activity occur on a fairly regular basis roughly every 11 years. This is frequently referred to as the solar cycle.

Data from the Solar Influences Data Analysis Center, World Data Center for the Sunspot Index, at the Royal Observatory of Belgium compiled by Hoyt & Schatten and NOAA. Image created by Robert A. Rohde / Global Warming Art

How do we gather this information? A core of ice drilled from the arctic was analyzed. The chart on the left shows the levels of protons with energies high enough to indicate that they came from solar events. Black values are estimated from levels of nitrates that form during solar events, red values are from directly observed cosmic rays. While other environmental factors can cause these spikes in nitrates, it's possible to cross-reference the events with data collected from lunar rocks, which aren't affected by weather (Straum, nd).
From the report made for the Department of Homeland Security by MITRE corporation, JASON department: Impacts of Severe Space Weather on the Electric Grid.

The Current Cycle:

Alvestad, Jan.

Coronal mass ejections (CME) often follow solar flares and increase in frequency and magnitude during the active parts of the solar cycle. The Sun ejects a blast of plasma mostly composed of electrons, protons, and highly excited gas at hundreds to thousands of miles per second. These ejections can reach the Earth as fast as eighteen hours, though most take closer to 2-3 days. Many of them miss the Earth completely, but sometimes they collide and interact with our own magnetosphere and atmosphere, causing auroras (bright lights in the sky) and also...

Geomagnetically Induced Current (GIC): You can create this phenomenon on a much smaller scale simply by sliding a bar magnet in and out of a coil of wire--the coil will become conductive as the magnetic field fluctuates and generate a small current, the same way crank generators work. Similarly, when the intensely charged particles in a CME hit the charged magnetosphere and ionosphere, fluctuations in the magnetosphere are produced, which can generate electricity in similar structures, in this case power lines and pipelines rather than a small piece of wire. The first significant observation of this phenomenon was in 1859 during a particularly intense storm known as the "Carrington Event" which produced enough current in unpowered wires to run (and damage) telegraph machines and other primitive electrical instruments. (NASA Science News, 2011) (Rohde 2006).

Infrastructure Impact

So, why does any of this matter on a practical level? It is difficult to gauge the full extent of the impact a severe solar event could have on modern civilization due to the intricate interrelations of every aspect of modern global economics and infrastructure. As illustrated below, the impacts on the electric power grid alone would have a variety of wide-ranging, impossible to forecast consequences.

The Department of Homeland Security, Office of Risk Management and Analysis Geomagnetic Storms: Evaluation of Risks and Risk Assessments has the following concise summary of the potential infrastructure impact of a severe geomagnetic storm.

Fortunately, cheap and effective failsafes have been engineered that could easily mitigate the associated risks of a severe solar storm, though simple technological failsafes have yet to be implemented in most of the world's developed countries. Unfortunately, despite their proven damaging effects on critical parts of electrical power grid, which are both costly and a threat to the security of our information and communications technology networks, few preparations have been made in most developed countries, including the United States of America, to mitigate potential infrastructure collapse relative to other natural disasters such as earthquakes, floods, wildfires, etc. (Department of Homeland Security, 2012a, 2012b). The NRC is currently considering amending its regulations to consider the possibility of damage to the electrical infrastructure that could potentially cause nuclear disasters as a result of nuclear power station cooling failure. (Borchardt, 2012; Johnson, 2012). The North American Electric Reliability Corporation outlined a variety of scenarios and proposals for action should a "High-Impact, Low Frequency Event" such as powerful geomagnetic storms, the detonation of a nuclear weapon at high altitude, or the use of a large-scale EMP weapon take place (NERC, 2010). The National Infrastructure Advisory Council also released a report and recommendations focusing on bolstering the resilience of the electrical infrastructure (NIAC, 2010)

“Severe geomagnetic storms can disrupt the operation of electric power transmission systems and critical infrastructures relying on space-based assets. A geomagnetic storm that degrades the electric power grid would affect not only the energy sector but the transportation, communications, banking, and finance sectors, as well as government services and emergency response capabilities… Extra-high-voltage transformers and transmission lines may be particularly vulnerable to geomagnetically induced currents caused by the disturbance of Earth’s geomagnetic field. The simultaneous loss of large numbers of these assets could cause a voltage collapse and lead to cascading power outages, resulting in significant economic costs to the Nation. An extreme geomagnetic storm is a low-probability, high-consequence event that could pose a systemic risk to the Nation” (Department of Homeland Security 2011, 1).

“Electrical power transmission networks face greater vulnerability to geomagnetic storms as they span longer distances to supply demand centers due to the use of high-voltage transmission lines.8 This is because the longer distances of networks make them better “antennas” to pick up the electrical currents induced by the geomagnetic storms. Geomagnetically induced currents can also overload electrical power grids, causing significant voltage regulation problems and, potentially, widespread power outages. Moreover, geomagnetically induced currents can cause intense internal heating in extra-high-voltage transformers, putting them at risk of failure or even permanent damage. Recent estimates state that 300 large extra-high-voltage transformers in the United States would be vulnerable to geomagnetically induced currents… Once fuel for backup power runs out, resupply of fuel (e.g., through gasoline pumps) is reliant on electricity. A power blackout lasting longer than 72 hours could create longer-term implications for interdependent infrastructures” (Department of Homeland Security 2011, 3).

The “Oak Ridge National Laboratory study documented past problems encountered in various types of equipment. The general conclusions are that the vulnerability of U.S. electric grid connections likely will rise due to the trends in industry and increasing use of extra-high-voltage equipment that is essential in modern electric power transmission” (Department of Homeland Security 2011, 7).

Transformers and Power Lines

While power lines have built-in arrestors to minimize the damage of sudden high voltage surges (such as those caused by lightning), the infrastructure is poorly designed to withstand the kind of current produced over large distances by GIC, which can damage devices in the power grid called "large power transformers" that transmit and distribute electricity.

Image by National Academy of Sciences. A more detailed state by state map can be found at NASA.

These transformers are costly to produce and, due to a variety of resource harvesting, transportation, and manufacturing factors, can only be produced in limited quantities. The United States consumes roughly 20% of the global market of large power transformers but produces less than 15% of that demand domestically between six factories. Due to the enormous variety of technical specifications for these large power transformers, limited supplies of copper and electrical steel, and bureaucracy surrounding their procurement, lead times to replacement can stretch to 20 months and beyond. Further, there are currently only 30 train cars capable of transporting large power transformers. These transformers fail over time and become less reliable as they age; in 2012, 70% of installed large power transformers were over 25 years old and their average life expectency is 40 years. It is estimated that there are currently around 2,000 "Extra High Voltage" (over 345 kilovolts) large power transformers installed in the United States. The total number of large power transformers is unknown, but likely in the tens of thousands, and at least 100 new ones have been installed every year since 2000 (see graphic below). Efforts are underway by the NERC to catalog the spares, but an industry figure shows that for every transformer design, 1.3 transformers are made, meaning severely limited interchangeability and spare reserves (Department of Energy, 2012). Even without factoring the impact of an economy fractured by catastrophe, optimal replacement time in the event of a severe solar event similar to the Carrington Event is estimated at 4 to 10 years (National Research Council for the National Academies, 2011; Kappenman, 2010).

(above: Department of Energy, 2012)

The Department of Homeland Security, Department of Energy, and several parties in the private industry have started a "Recover Transformer (RecX)" program to attempt to address this issue by creating smaller and easier to transport, faster to produce, and generally easier to replace in the event of a catastrophic failure (Department of Homeland Security, 2012a). The prototype was produced by ABB and was installed in an emergency drill during April of 2012, a process which took roughly a week (a vast improvement on typical transportation and installation times). The test model can replace roughly 500 of the 2,000 EHV LPTs installed and covers 90% of the transformers in its voltage class (the largest voltage class of EHV transformers) (Wald, 2013; Department of Energy, 2012).

(Armed Forces Communication and Electronics Association Cyber Committee, 2013)

According to Craig L. Steigemeier, Business Development & Technology Director, ABB:

"The RecX units already built could be redeployed in the event of an emergency. Storage and deployed locations are not public information. And since a 345/138kV auto with a somewhat high impedance doesn't cover everthing in terms of large auto's on the grid, we have completed other designs at other ratings. We are also exploring variants based on the design for other applications."


It is costly to build protection against solar radiation damage into a satellite, and it is currently impossible to build a satellite that is fully immune to the impact of solar weather (Linton, 2012). In November 2003, solar eruptions caused an estimated $4 billion to $10 billion in damage, largely due to the destruction and disruption of satellites. This also forced the rerouting of numerous flights, costing $10,000 to $100,000 each and disruption of commerce by incapacitating navigational satellites (National Research Council for the National Academies, 2011). It is difficult for obvious reasons to put an exact dollar cost on the disruption of daily life and business caused by cell phone disruption, personal GPS device malfunction, and all the other mundane goods and services dependent upon satellites.

Transportation Systems

The direct impact of GIC or even a fairly strong EMP on most automobiles is negligible: the circuits are too small to induct current and the semiconductors are too rugged to be permanently damaged (Foster, 2004). Nonetheless, cars cannot run without gasoline and gasoline cannot be pumped without electricity.

Oil and Gas Pipelines

Damage has been observed taking place on large pipelines as a result of current induced between the pipe itself and the ground (pipe-to-soil voltage). (Hejda, P. and Bochni ́ıˇcek, J., 2005)

Personal Technology

Cell phones and GPS devices require satellites to function.



Large Power Transformer/Extra High Voltage Large Power Transformer (LPT/EHV LPT): The definition of what constitutes a "large power transformer" or "extra high voltage" vary throughout the electrical industry, but common definitions are that LPTs are over 100 MVA and EHV LPTs are rated for 345 kilovolts or more.

Other Useful Conversions with Calculators


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