Our sun is a restless star. When particularly active, it can emit effervescent packets of magnetic energy and charged particles known as sunlight. If it releases a smaller flare aimed at Earth, the solar material can produce harmless but spectacular exhibits of auroras as it slams into our atmosphere.
But more powerful solar outbreaks can cause geomagnetic storms that cause destruction in the Earth's magnetic bubble, potentially causing serious damage to the planet's electrical infrastructure. (See photos of solar storms made in the laboratory.)
And as it turns out, your city's ability to reverse a powerful geomagnetic storm may depend on the types of rock beneath your feet.
Recent studies by U.S. Pat. The Geological Survey analyzed how different flavors merge with geomagnetic storms in the northeastern United States. The work shows that the potential damage to electrical networks can either be amplified or diminished significantly from the regional rock types. For example, people living on New England Highlands are at greater risk of experiencing major injuries during a geomagnetic storm, the survey shows, while those in the Mid-Atlantic Coastal Plain have a much lower risk.
Researchers have known for some time that geology plays a key role in sun damage. But the study of love, which was published in December in the journal Space Weather, go one step further by accurately quantifying how geological differences control the potential damage at specific locations in the US northeast. And although this study only focuses on part of a country, it has global implications.
Right now, there is a lack of detailed data on regional geomagnetic risks, as well as on the frequency and intensity of the solar storms and the response of our technologies to them. This means that risk assessments of the spacecraft are several decades behind the threat analyzes of hazards such as hurricanes and earthquakes, making mitigation planning "extremely challenging," said Edward Oughton, senior researcher at Oxford University's Environmental Change Institute. Implementing more detailed regional mapping of geoelectric risks will help fill the gaps, and Australian and Chinese initiatives in this direction are already underway.
"In the big schemes of things, it is not very expensive to undertake these studies and collect geomagnetic data," said study leader Jeffrey Love, a geoscientist of the USGS & Geomagnetism Program. "But it takes initiative to do so."
Interplanetary electric boogaloo
Strong sunsets must not be taken lightly. When the sun launches a strong flare toward Earth, the electromagnetic energy hits the planet at the speed of light. This causes particles in the upper atmosphere and causes radio signal interference. If a flare is strong enough, radio communications used by airlines and satellite-based navigation networks will malfunction or stop functioning altogether.
About 30 minutes later, a large stream of electrons and protons arrive near the speed of light. This attack destroys electronic circuits on satellites, and any astronaut outside the Earth's magnetic bubble can get a potentially life-threatening radiation dose.
Then, 18 hours to several days after the onset of the event, a colossal plasma shadow known as a coronal mass ejection can fall into the Earth's magnetic bubble at 1,900 miles per second. These processes are capable of creating major disturbances in our planet's magnetic field, known as geomagnetic storms.
If they are strong enough, such storms can cause strong electric currents in very long conductive structures in the mains, causing severe and sometimes permanent damage to them. This can trigger widespread blackouts; A 1989 geomagnetic storm led to light that went beyond Quebec. During the Vietnam War, extremely high space was found to cause sea mines offshore from Vietnam to explode.
One of the strongest largest geomagnetic storms on record, Carrington Event 1859, disturbed telegraph systems, and operators got electric shock. The storm excluded auras as far south as Hawaii, and people found that they could read newspapers outside even at night. If a similar event occurred today, it would very likely lead to widespread and extremely expensive destruction for our increasingly electrified infrastructure.
Supercharging a solar storm
On a regional scale, the underlying geological makeup can have a very significant influence on the damage potential of the storm. Sedimentary rocks tend to have pores containing water, making them electrically conductive, says Ciaran Beggan, a geophysicist with the British geological survey. Metamorphic and rocky stones are denser and less porous and are more electrically resistive.
However, during a geomagnetic storm, migratory magnetic activity induces electric currents on the surface of the planet, which can cause problems for a city built on metamorphic or rocky stones. Although the power cannot easily flow through these rocks, "if you have shorted the earth's insulating part with a mains, it flows right through it," causing damage, love says.
This means that when the next major geomagnetic storm hits, "a power grid in part of Europe may be just fine, but another just a few hundred miles away can be severely affected by the same event," said Juha-Pekka Luntama, head of Room Weather for the European Space Agency's Space Situational Awareness Program.
When the next major geomagnetic storm hits, "one power grid in part of Europe may be just fine, but another just a few hundred miles away can be seriously affected by the same event."
This effect applies to regions worldwide. For example, north of Scotland has lots of resistive rocks, which means that its mains risk experiencing dangerously strong geoelectric fields, Beggan says. Conversely, the south of England is generally packed with low-risk sedimentary rocks.
Coast complicates matters. Along the coasts you have both resistive sand and conductive seawater. It can create a "channeling effect, whereby the power is built up along the coast," Beggan says. It's bad news for all the mains running along the coast.
For their latest work, the Love Team obtained records of magnetic storms detected at the observatories, and then combined them with new studies that measured the local magnetic field and its related electric field. By doing so, they could calculate the electrical currents that escaped past geomagnetic storms, which can be used to model future events of similar strength.
The team found that the risk varies significantly from region to region, with some electrically resistant rocks that increase regional geoelectric risk by a factor of one hundred. The huge amounts of stiff and metamorphic rocks in the Appalachian Mountains mean that the mains sit on top of them, will suffer greatly the next time the sun becomes furious.
The way the electricity grid is oriented also plays a role, says love. Electric lines running perpendicular to the appalaches increase the potential of damage more than a grid running parallel to them.
Star down in the sun
We also need to know how often powerful geomagnetic storms occur. Unfortunately, modern instrumentation has documented them for only about 70 years, which means that our record is rude at best. (Find out how scientists monitor solar energy activity that probably prevented war war values from breaking out in 1967.)
Therefore, some researchers have tried to dig up older data. In a PNAS study released earlier this month examined a team led by Raimund Muscheler from Lund University chemical fingerprints in tree rings and ice cores and found evidence of a solar storm that hit the ground around 660 B.C. This storm was 10 times stronger than a known strong solar storm that hit in 1956.
However, the data remains very noisy, so finding a real solar storm is a difficult task, it is a difficult task, says Muscheler: "I currently miss everything between the very big events [like the one in 660 B.C.] and 1956-size events, "he says.
At the same time, the European Space Agency is among several groups working on ways to see future storms brew in time to mitigate their effects.
If funding is secured at the end of November, ESA's Lagrange mission will sit near the sun, watch and warn the ground for any incoming paroxysms. In this way, just before Earth and Sun renew their dangerous alliance, power companies could open as many circuits as possible to spread excess electricity throughout the system.