Getting Familiar with Space Weather: What Happens at the Earth During a Day of Stormy Weather in Space?

Although they both shine brightly, it turns out that the Sun is nothing like Las Vegas—bad behavior at the Sun does not always stay at the Sun.  When the Sun behaves badly, it hurls light, high energy particles, and tons of magnetized plasma indiscriminately out into the solar system. The different facets of stormy space weather describe what happens when these sporadic outbursts hit the Earth.

On the surface of the sun arise regions of intense activity, solar storms, that can last for months.  In these areas, the intense loops of magnetic field that emerge through the surface of the sun violently thrash about, as seen in the Solar Dynamics Observatory (SDO) image below.  Occasionally two different loops of magnetic field are thrown together with sufficient force to cause them to break and reconnect with the magnetic field of the other loop (the laws of electromagnetism tell us that magnetic field lines can never end, but they can break and immediately connect to a different field line). After this magnetic reconnection, the magnetic field snaps back like a stretched rubber band, releasing a vast amount of magnetic energy as motion of the rebounding plasma.  The change in the magnetic field can release billions of tons of magnetized solar plasma, with some eruptions so ferocious that this magnetic tsunami escapes the gravitational pull of the Sun entirely and barrels out into the solar system.

1-13-15_flare_171-131.jpgSolar Storms and an M-class Solar Flare: An x-ray image of the sun, showing a number of solar storms, area where intense loops of magnetic field violently thrash about.  On the right limb of the sun, an M-class flare is seen erupting from one of these solar storm regions. the intensely blinding x-rays from a class X7 solar flare. Credit: NASA/SDO.

The intense snap back of the magnetic field can also accelerate electrons down towards the Sun’s surface; when those electrons impact the dense plasma of the Sun, they can generate a blinding solar flare. In addition, all of the energy released in an intense solar storm can lead to the acceleration of protons to nearly the speed  of light, showering a section of the solar system in a proton hailstorm. All of these processes drive the space weather that can wreak havoc on critical infrastructure including, the electrical power grid, satellite communications and GPS navigation, and Earth orbiting astronauts and satellites.

What SPF Sunblock Do I Need for This?

The story of stormy weather in space invariably begins with the volatility of the Sun’s magnetic field. Much like the Earth, the magnetic field of sun is generated below its surface by a magnetic dynamo, a process by which internal motions of the plasma that make up the Sun generate powerful magnetic fields.  The surface of the Sun is not solid like the rocky planets that orbit around it, but is more like the surface of a boiling pot of water. Hot plasma from deep down in the Sun rises, and cool plasma at the surface sinks; together these boiling motions effectively move heat, generated by nuclear fusion reactions in the Sun’s core, to the surface where that heat is radiated away as the spectrum of sunlight, like a 6,000 degree Celsius light bulb in the sky.  But embedded in the Sun’s plasma is a magnetic field, and that magnetic field is dragged around and strengthened by these boiling motions. Scientists have yet to understand all of the details of the dynamo process, either in the Sun or in the Earth, but the consequences of the solar dynamo are clear:  the strong magnetic fields generated below the surface by the dynamo become buoyant, causing loops of the magnetic field to rise up through the solar interior and eventually burst through the surface of the Sun. These emerging magnetic fields fill the atmosphere of the Sun, or solar corona, with a chaotic tangle of loops of intense magnetic field.

festooningloops.jpgSolar Storms and an M-class Solar Flare:  Loops of magnetic field seen in the solar corona observed in extreme ultraviolet light. These magnetic fields loops are in constant motion, jostled by the boiling motions of the solar surface below. Credit: NASA/SDO.

This snarl of magnetic fields in the solar corona is not stagnant, but rather these loops are in constant motion, jostled by the boiling motions of the plasma at the surface from which the loops emerged, as pictured above from SDO observations in extreme ultraviolet light. When two loops of magnetic field pointing in different directions are shoved together by all of this frenetic motion, those magnetic field lines can break and reconnect, freeing them to snap back like a stretched rubber band.  Electrons in the tenuous coronal plasma connected to these rebounding magnetic field lines can be catapulted towards the dense plasma at the Sun’s surface. The collisions of these electrons with the Sun’s plasma below can sometimes trigger a brilliant solar flare, blasting the solar system with a deluge of powerful x-rays.

What happens when the intense x-rays from a powerful solar flare reach the Earth?  Fortunately, the Earth’s atmosphere shields the surface of the Earth from the harmful effects of this blast of x-rays, which can damage your DNA at the atomic level, so we don’t need to find a new sunblock with the same SPF (Sun Protection Factor) as block of lead.  But this protection from solar flare x-rays comes at a price for the atmosphere.

When the x-rays from the solar flare bombard the thin air in the Earth’s upper atmosphere, they can tear apart the neutral air molecules, shredding them into their constituent positive ions and freely flying electrons, a process called ionization.  At an altitude of about 40 miles, the neutral upper atmosphere transitions into the ionosphere, where the density of ions and electrons begins increasing with altitude. The resulting surge in the ionization of the upper atmosphere by the x-rays of a solar flare, an ionization storm, can disrupt many of the advanced technologies central to our modern lifestyles.

The primary casualty of a severe ionization storm is communication by radio.  You may think that this is not so bad—poor reception of your local FM radio station during your favorite song is annoying, but hardly a cause to raise alarm.  But radio communications are essential to a broad range of modern technology, from satellite TV to GPS navigation to maintaining safe conditions for the more than 10,000 commercial, private, and military aircraft that may be in the air around the world at any one time.

Proba-V_detecting_aircraft.pngWorldwide Aircraft:  Image of data from the Proba-V mini-satellite operated by the European Space Agency (ESA), showing signals from more the 15,000 separate aircraftCredit: ESA/DLR/SES

Radio waves used for communications from satellites must travel through the ionosphere to reach the Earth, and dramatic jumps in the ionization can interfere with, or even completely cut off, these communications.  Loss of satellite communications may mean more than missing your favorite primetime show on DirecTV—the refraction of radio waves through variations in ionospheric density can lead to errors in GPS triangulation, or the signal could be entirely lost, causing serious problems for the growing number of travelers dependent on GPS for navigation.  During extreme ionization storms, radio communications to aircraft flying efficient polar routes for transcontinental air travel are blacked out completely, requiring re-routing of those flights on longer flight paths. The cascade of delays and increased fuel costs can lead to losses amounting to tens of millions of dollars per year.  Even amateur ham radio operators depend on the ionosphere, bouncing their transmissions off of the ionosphere to reach destinations beyond the local horizon, a phenomenon known as skywave propagation.  Abrupt changes or irregularities in the ionization level can lead to poor reception or even cut off their transmissions entirely.

Skywave.jpg

 

Skywave Propagation:  Illustration of the bouncing of radio waves off of the ionosphere (red layer) to beat the curvature of the Earth and communicate with locations beyond the local horizon. Credit: Wikipedia/Creative Commons

 

It’s a Hail of a Day to Be in Space

A blast of x-rays from a powerful solar flare is just the tip of the iceberg of ways in which the sun can cause havoc in space. Although scientists still remain uncertain of how it happens, particularly violent storms on the Sun’s surface can also lead to the acceleration of protons, as well as electrons and heavier ions such as helium, to around 200 million miles per hour, about 1/3 of the speed of light.  Like the shot from a sawed-off solar shotgun, these protons blast out through a section of the solar system, woe to anyone or anything in its way, reaching the Earth in just twenty-four minutes.

Proton hailstorms are a serious hazard for astronauts orbiting the Earth, such as those residing on the international space station, and quick action is necessary to take shelter.  Since the fastest that information can travel is the speed of light, if a violent solar storm on the Sun’s surface triggers a proton hailstorm, it takes eight minutes for the light that typically accompanies the blast of protons to reach the astronauts.  That leaves just sixteen more minutes for the astronauts to reach a sheltered room of the space station before the barrage of protons arrives. If an astronaut is out on a spacewalk at the time, sixteen minutes may indeed not be enough time to return to the safety of the station.

This inherently short warning time for proton hailstorms is why one of the primary missions of the U.S. government’s Space Weather Prediction Center, run by the National Oceanographic and Atmospheric Administration (NOAA), is to generate predictions about space weather conditions.  Only during an all-clear period, when there is no imminent threat of a solar storm that might spark a proton hailstorm or other inclement space weather, will tasks be undertaken requiring astronauts to leave the relative safety of the space station.  If an astronaut were to be caught outside, this bombardment of protons would pass right through the spacesuit, damaging her DNA at an atomic level—if not instantly killing her, this massive dose of high energy protons would almost certainly prove fatal in the short term.

But human beings, with their the delicate biology, are not the only victims that may suffer casualties from a severe proton hailstorm. The sensitive electronics at the heart of communications satellites can also be damaged by the energetic protons and other particles arising from proton hailstorms. In addition, the high energy protons and electrons trapped in the Earth’sVan Allen Radiation Belts, which can be dramatically boosted during periods of severe space weather, can also harm spacecraft circuitry. Spacecraft anomalies, as they are so quaintly called, can be caused by proton hailstorms, and can lead to anything from minor performance glitches to the total loss of a $200 million satellite.

SpaceWeather_SEP_Satellite_ESA.jpgProton Hailstorm Damaging a Satellite:  Artist’s rendition of a proton hailstorm impacting a satellite, causing damage to the spacecraft electronics Credit: ESA.

Proton hailstorms also present a major complication for any future attempt for astronauts to reach Mars, or any other planet in our solar system. Ingenuity is essential to keep the launch mass to a minimum, while still providing the shielding necessary to safeguard the lives of any interplanetary explorers in the face of an intense proton hailstorm.

Here Comes the Big One

Although solar flares and proton hailstorms indeed can impact our technology and cause hundreds of million of dollars in damage to our technological infrastructure, the true behemoth of space weather is the magnetic tsunami. Particularly intense solar storms on the surface of the Sun can sometimes trigger the eruption of a huge mass of plasma and magnetic fields that steamrolls its way straight from the Sun and out through the solar system at up to five million miles per hour.  If the Earth happens to be in the path of this colossus, it’s impact on the protective magnetic field of the Earth can set off a magnetic storm.

cme-graphic_full.jpgMagnetic Tsunami:  Artist’s depiction of a magnetic tsunami that has erupted from a storm on the solar surface and is barreling out into the solar system. Credit: NASA.

The crush of this fast-moving ball of plasma, which can total several billion tons, can compress the Earth’s magnetic field, often tearing into this magnetic shield and dumping a tremendous number of ions and electrons from the Sun directly into the the Earth’s magnetosphere. The injected ions begin circulating westward around the Earth at about 25,000 miles per hour at an altitude of 10,000 to 20,000 miles above the surface, circling the Earth about once per hour.  The electrons orbit the Earth eastward at about 2,500 miles per hour, taking about 10 hours for each lap. Together, these extra particles can dramatically increase the electrical current, known as the ring current, that always flows westward around the Earth.  Maxwell’s equations of electromagnetism tell us that flowing electrical currents generate magnetic fields, and the magnetic field created by this boost in current around the Earth opposes the Earth’s internally generated magnetic field.

The upshot of all of this complex activity, which remains a topic of active study by space scientists, is that the magnetic field at the surface of the Earth can be reduced by a few percent during a particularly severe magnetic storm. Now, one may think that a drop in the Earth’s magnetic field of a few percent, which would barely deflect a compass needle, can hardly make much of a difference.  But the size of the relative change in the magnetic field doesn’t really matter, instead it is what happens within our electrical power grid when  the magnetic field changes at all.

One of the fundamental equations of electromagnetism, Faraday’s Law, tells us that when the magnetic field passing through a loop of wire changes, it induces a voltage in that loop of wire.  This is, in fact, the fundamental principle used to generate electricity at power plants, but during a magnetic storm Faraday’s Law can cause havoc.  The loops of wire that are affected by geomagnetic storms are the high-tension wires of our electrical power grid that are used to carry electricity from one location to another.  At the scale of the Earth, our power grid looks like a bunch of closed loops of wire of different shapes and sizes laying flat on the Earth’s surface.  The potentially disastrous effect of Faraday’s Law on our power grid is due to the size of these closed loops of wire: closed loops made up of power lines can cover areas that are tens to hundreds of miles across, and a large amount of the magnetic field can pass through that large area.  Even a small change in the strength of Earth’s magnetic field, when summed up over the immense size of these loops in our power grid, can lead to a massive voltage spike of thousands of volts in the system.  It’s similar to a light drizzle of rain falling on  a very large concrete parking lot—although the amount of rain in one area is not much, the water falling over the entire parking lot adds up to a lot.

When a voltage is applied to a wire, it drives a current through that wire.  The changes is the Earth’s magnetic field due to a magnetic storm generate huge voltages that drive geomagnetically induced currents in our power grid.  These currents can overwhelm critical components, such as the massive transformers—each nearly the size of a small house—that are critical elements needed to transfer electricity efficiently over long distances.  In March 1989, an intense magnetic storm sparked geomagnetically induced currents that blew up one of these massive transformers in Quebec, Canada, leaving three million people without electricity for nine hours.

PowerGrid_Quebec.jpgTransformer Damage from Magnetic Storm:  (Left) Image of electrical lighting visible from space at night on the eastern seaboard of North America. (Upper right) Typical size of an electrical power transformer. (Lower right) Damage to one of these transformers in Quebec, Canada due to a severe magnetic storm on March 13, 1989. 

But the destruction of a single massive transformer and the loss of electricity for a good chunk of a day is just a small taste of how wrong things can go during a magnetic storm.  Much larger magnetic tsunamis have occurred in the past, with the most recent being the Carrington Event in 1859, and estimates are that today a similar magnetic tsunami from the Sun and the consequent magnetic storm at Earth could cause an estimated trillion dollars worth of damage.  If not just one, but a dozen or more, of the transformers were destroyed, it could take months to restore electrical service to some areas.  The reason is that, at any one time, only a few spare  transformers exist.  If a major magnetic storm were to destroy dozens of these vital components of our power grid at once, it could take months to build the necessary replacements for recovery.

How would your life change if one morning you woke up to discover that the power was out, and would not be restored for at least three months.  If you have teenagers, particular, it could be quite bad.  Since everything is dramatic to a teenager, how catastrophic would be the loss of electrical power to charge their cell phones and run their laptops and video games systems?

Oh, but wait, the fun doesn’t end there.  All of those ions and electrons dumped by the magnetic tsunami into the Earth’s magnetosphere don’t just circle the Earth harmlessly until they are eventually scattered and lost.  They also increase the density of high-energy protons and electrons in the Earth’s Van Allen Radiation Belts, able to directly damage satellites that operate in orbit around the Earth.

On January 13, 1994, a major magnetic storm dumped a huge amount of plasma into the Van Allen Radiation Belts.  The cumulative effect of the additional high-energy protons and electrons in the radiation belt affected the guidance systems of the Intelsat K, Anik E-1, and Anik E-2 communications satellites.  Although Intelsat K began to wobble and lost antenna coverage, a backup system enabled normal operation to be recovered by the end of the day.  But the intensity of the high-energy protons and electrons caused the guidance systems on both Anik E-1 and E-2  to fail, and both began to spin out of control.  Although the backup guidance system of E-1 was able to stabilize the spacecraft within 8 hours, the backup system failed on E-2, and it appeared the satellite might be a total loss.  But clever engineers were able to use ground control for the satellite thrusters to eventually bring the satellite under control, but it took five months and cost $50 million dollars for the heroic efforts to save the satellite, finally restoring the spacecraft to service in August 1994.

Finally, the boosted plasma density at satellite orbits during geomagnetic storms increases the drag on satellites, requiring the use additional fuel to keep the spacecraft in its nominal orbit.  Over time, the extra use of fuel will shorten the overall lifetime of satellites, because they will run out of the fuel needed to correct their orbits.

So Is There Any Good News?

Solar flares, proton hailstorms, and magnetic storms may sound like a lot of inconvenience to you, interrupting your favorite satellite TV transmissions or preventing you from charging your cell phone, but it’s not all bad.  Just like the fun of watching lightning dancing in the sky from your bedroom window during a thunderstorm, space weather leads to one of the best shows on Earth: the aurora.  Although it occurs at such a high latitude that few people ever get the chance to see the northern lights for themselves, there’s plenty of opportunity nowadays to view this natural light show on the internet, even some mind-blowing views from the international space station flying over the aurora, as seen below.  Next time, join me as we delve into the domino effect of space weather occurrences that leads to the light show of the aurora.

24204469670_22435fdeab_o.jpgThe Aurora Borealis seen from the International Space Station:  NASA astronaut Scott Kelly and ESA astronaut Tim Peake shot this beautiful image of the aurora over the Pacific Northwest from the International Space Station on January 20, 2016. Credit: ESA/NASA.

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