Solar Flares 3 (How do Solar Flares Affect Electronics and Communication?)

As electromagnetic waves, and in this case, radio signals travel, they interact with objects and the media in which they travel. As they do this the radio signals can be reflected, refracted or diffracted. These interactions cause the radio signals to change direction, and to reach areas which would not be possible if the radio signals travelled in a direct line.

The condition of the Sun has a major impact on ionospheric radio propagation. Accordingly it affects a variety of forms of HF radio communications including two way radio communications, maritime mobile radio communications, general mobile radio communications using the HF bands, point to point radio communications, radio broadcasting and amateur radio communications.

As the Sun provides the radiation that governs the state of the ionosphere and hence HF radio propagation, any flares or other disturbances are of great importance. Under some circumstances these can enhance radio communications and the HF radio propagation conditions. Under other circumstances they can disrupt radio communications on the HF bands, while at the same time providing some radio propagation conditions that can be used at VHF by radio amateurs.

there are a number of types of disturbance that are of particular interest for radio communications. Flares are one of the most obvious. However, apart from solar flares there are other disturbances that occur. One is the coronal mass ejection, and there are also coronal holes.

The US power grid is a complex electrical apparatus that has well-known sensitivities to space weather disturbances. Recent changes in its design and utilization have significantly reduced its operating margins to supply us with on-demand electricity. This means there is less flexibility available with which to deal with power shortages and blackouts.

Space weather events can damage equipment over wide geographic regions so that recovery delays become substantially longer and more costly.

                                                                                             

The 23rd Cycle - Chapter 4 - Describes in detail the state of the US power grid, and the forces which are driving it to be far more vulnerable to solar storms than at any time in the past.

"As North America has evolved into a unified power-sharing network of regions, each buying and selling a diminishing asset, US domestic power has become more vulnerable to solar storms buffeting the power grid in the more fragile northern-tier states and Canada. So long as one region continues to have a surplus at a time when another region needs a hundred megawatts, power is 'wheeled' through 1000-mile power lines to keep supply and demand balanced across the grid. In 1972, a typical utility might need to conduct only a few of these electromagnetic transactions each week. Now, it is common for thousands to be carried out, often by computer, in much the same way that stocks are traded on Wall Street...

The electrical power grid is composed of many elements, and you can think of it as a set of rivers flowing overhead. Large rivers carry the electricity from distant generation stations (Dams, Hydroelectric Facilities and Nuclear Plants) on supply lines of 138,000 volts or higher. These are carried as three cables (2 'hot' and one defining the 'ground' in a 3-phase system) suspended atop 100-foot tall towers that you will see out in many rural areas. These supply cables terminate at regional substations where the high voltages are converted into lower voltages from 69,000 volts to 13,800 volts. These lines then enter your neighborhoods atop your local telephone poles where a neighborhood transformer steps this voltage down to 220 and supplies a dozen or so individual houses

When space weather disturbances cause 'Geomagnetically Induced Currents' , these GICs can enter a transformer through its Earth ground connection. The added DC current to the transformer causes the relationship between the AC voltage and current to change at the source of the electricity, not just where it is delivered to your electrical appliance. Because of the way that GIC currents affect the transformer, it only takes a hundred amperes of GIC current or less to cause a transformer to overload during one-half of its 60-cycle operation. As the transformer switches 60 times a second between being saturated and unsaturated, the normal hum of a transformer becomes a raucous, crackling whine. Regions of opposed magnetism as big as your fist in the core steel plates crash about and vibrate the 100-ton transformer nearly as big as a house in a process that physicists call magnetostriction.

The impact that magnetostriction has upon specific transformers is that it generates hot spots inside the transformer where temperatures can increase very rapidly to hundreds of degrees in only a few minutes. Temperature spikes like these can persist for the duration of the magnetic storm which, itself, can last for hours at a time. During the March 1989 storm, a transformer at a nuclear plant in New Jersey was damaged beyond repair as its insulation gave way after years of cumulative GIC damage. Allegheny Power happened to be monitoring a transformer that they knew to be flaky. When the next geomagnetic storm hit in 1992. They saw the transformer reply in minutes, and send temperatures in part of its tank to more than 340 F (171 C). Other transformers have spiked fevers as high as 750 F (400 C). Insulation damage is a cumulative process over the course of many GICs, and it is easy to see how cumulative solar storm and geomagnetic effects were overlooked in the past.

Outright transformer failures are much more frequent in geographic regions where GICs are common. The Northeastern US with the highest rate of detected geomagnetic activity led the pack with 60% more failures. Not only that, but the average working lifetimes of transformers is also shorter in regions with greater geomagnetic storm activity. The rise and fall of these transformer failures even follows a solar activity pattern of roughly 11 years.

If your power plant is located over a rock stratum with low resistance, any geomagnetic disturbance will cause a bigger change in the voltages it induces in your local ground, and the bigger this change in ground voltage, the stronger will be the GIC currents that flow into your transformers. Typical daily GICs can run at about 5-10 amperes, but severe geomagnetic storms can cause 100-200 amperes to flow

A conservative estimate of the damage done by GICs to transformers by Minnesota Power and Electric was $100 million during a solar-maximum period. This includes the replacement of damaged transformers, and the impact of shortened operating lifetimes due to GIC activity

Solar Flares 2 (Carrington's events)

A Super Solar Flare

May 6, 2008: At 11:18 AM on the cloudless morning of Thursday, September 1, 1859, 33-year-old Richard Carrington—widely acknowledged to be one of England's foremost solar astronomers—was in his well-appointed private observatory. Just as usual on every sunny day, his telescope was projecting an 11-inch-wide image of the sun on a screen, and Carrington skillfully drew the sunspots he saw.

Right: Sunspots sketched by Richard Carrington on Sept. 1, 1859. Copyright: Royal Astronomical Society: more.

On that morning, he was capturing the likeness of an enormous group of sunspots. Suddenly, before his eyes, two brilliant beads of blinding white light appeared over the sunspots, intensified rapidly, and became kidney-shaped. Realizing that he was witnessing something unprecedented and "being somewhat flurried by the surprise," Carrington later wrote, "I hastily ran to call someone to witness the exhibition with me. On returning within 60 seconds, I was mortified to find that it was already much changed and enfeebled." He and his witness watched the white spots contract to mere pinpoints and disappear.

It was 11:23 AM. Only five minutes had passed.

Just before dawn the next day, skies all over planet Earth erupted in red, green, and purple auroras so brilliant that newspapers could be read as easily as in daylight. Indeed, stunning auroras pulsated even at near tropical latitudes over Cuba, the Bahamas, Jamaica, El Salvador, and Hawaii.

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Even more disconcerting, telegraph systems worldwide went haywire. Spark discharges shocked telegraph operators and set the telegraph paper on fire. Even when telegraphers disconnected the batteries powering the lines, aurora-induced electric currents in the wires still allowed messages to be transmitted.

"What Carrington saw was a white-light solar flare—a magnetic explosion on the sun," explains David Hathaway, solar physics team lead at NASA's Marshall Space Flight Center in Huntsville, Alabama.

Now we know that solar flares happen frequently, especially during solar sunspot maximum. Most betray their existence by releasing X-rays (recorded by X-ray telescopes in space) and radio noise (recorded by radio telescopes in space and on Earth). In Carrington's day, however, there were no X-ray satellites or radio telescopes. No one knew flares existed until that September morning when one super-flare produced enough light to rival the brightness of the sun itself.

"It's rare that one can actually see the brightening of the solar surface," says Hathaway. "It takes a lot of energy to heat up the surface of the sun!"

Above: A modern solar flare recorded Dec. 5, 2006, by the X-ray Imager onboard NOAA's GOES-13 satellite. The flare was so intense, it actually damaged the instrument that took the picture. Researchers believe Carrington's flare was much more energetic than this one.

The explosion produced not only a surge of visible light but also a mammoth cloud of charged particles and detached magnetic loops—a "CME"—and hurled that cloud directly toward Earth. The next morning when the CME arrived, it crashed into Earth's magnetic field, causing the global bubble of magnetism that surrounds our planet to shake and quiver. Researchers call this a "geomagnetic storm." Rapidly moving fields induced enormous electric currents that surged through telegraph lines and disrupted communications.

"More than 35 years ago, I began drawing the attention of the space physics community to the 1859 flare and its impact on telecommunications," says Louis J. Lanzerotti, retired Distinguished Member of Technical Staff at Bell Laboratories and current editor of the journal Space Weather. He became aware of the effects of solar geomagnetic storms on terrestrial communications when a huge solar flare on August 4, 1972, knocked out long-distance telephone communication across Illinois. That event, in fact, caused AT&T to redesign its power system for transatlantic cables. A similar flare on March 13, 1989, provoked geomagnetic storms that disrupted electric power transmission from the Hydro Québec generating station in Canada, blacking out most of the province and plunging 6 million people into darkness for 9 hours; aurora-induced power surges even melted power transformers in New Jersey. In December 2005, X-rays from another solar storm disrupted satellite-to-ground communications and Global Positioning System (GPS) navigation signals for about 10 minutes. That may not sound like much, but as Lanzerotti noted, "I would not have wanted to be on a commercial airplane being guided in for a landing by GPS or on a ship being docked by GPS during that 10 minutes."

Right: Power transformers damaged by the March 13, 1989, geomagnetic storm: more.

Another Carrington-class flare would dwarf these events. Fortunately, says Hathaway, they appear to be rare:

"In the 160-year record of geomagnetic storms, the Carrington event is the biggest." It's possible to delve back even farther in time by examining arctic ice. "Energetic particles leave a record in nitrates in ice cores," he explains. "Here again the Carrington event sticks out as the biggest in 500 years and nearly twice as big as the runner-up."

These statistics suggest that Carrington flares are once in a half-millennium events. The statistics are far from solid, however, and Hathaway cautions that we don't understand flares well enough to rule out a repeat in our lifetime.

And what then?

Lanzerotti points out that as electronic technologies have become more sophisticated and more embedded into everyday life, they have also become more vulnerable to solar activity. On Earth, power lines and long-distance telephone cables might be affected by auroral currents, as happened in 1989. Radar, cell phone communications, and GPS receivers could be disrupted by solar radio noise. Experts who have studied the question say there is little to be done to protect satellites from a Carrington-class flare. In fact, a recent paper estimates potential damage to the 900-plus satellites currently in orbit could cost between $30 billion and $70 billion. The best solution, they say: have a pipeline of comsats ready for launch.

Humans in space would be in peril, too. Spacewalking astronauts might have only minutes after the first flash of light to find shelter from energetic solar particles following close on the heels of those initial photons. Their spacecraft would probably have adequate shielding; the key would be getting inside in time.

No wonder NASA and other space agencies around the world have made the study and prediction of flares a priority. Right now a fleet of spacecraft is monitoring the sun, gathering data on flares big and small that may eventually reveal what triggers the explosions. SOHO, Hinode, STEREO, ACE and others are already in orbit while new spacecraft such as the Solar Dynamics Observatory are readying for launch.

Research won't prevent another Carrington flare, but it may make the "flurry of surprise" a thing of the past.

Solar Flares 1 (What is Solar Flares?)

Solar flares

Solar flares are enormous explosions that occur on the surface of the Sun. They result in the emission of colossal mounts of energy. In addition to this, the larger solar flares also eject large amounts of material mainly in the form of protons.

Flares erupt in just a few minutes with apparently no warning. When they occur the material is heated to millions of degrees Celsius and it leaves the surface of the Sun in a huge arch, returning some time later. The flares normally occur near sunspots, often along the dividing line between them where there are oppositely directed magnetic forces.

It is the magnetic fields appear to be responsible for the solar flares. When the magnetic field between the sunspots becomes twisted and sheared the magnetic field lines may cross and reconnect with enormous explosive energy. When this occurs an eruption of gases takes place through the solar surface, and it extends several tens of thousands of miles out from the surface of the Sun and follow the magnetic lines of force to form a solar flare. The gases from within the sun start to rise and the area becomes heated even more and this causes the level of visible radiation and other forms of radiation to increase.

Solar flare
Image courtesy NASA

During the first stages of the solar flare, high velocity protons are ejected. These travel at around a third the speed of light. Then, about five minutes into the solar flare, lower energy particles follow. This material follows the arc of the magnetic lines of force and returns to the Sun, although some material is ejected into outer space especially during the larger flares.

Effect of solar flares:   For most solar flares, the main effect felt on Earth is an increase in the level of solar radiation. This radiation covers the whole electromagnetic spectrum and elements such as the ultra-violet, X-rays and the like will affect the levels of ionisation in the ionosphere and hence it has an effect on radio communications via the ionosphere. Often an enhancement in ionospheric HF propagation is noticed as the higher layers of the ionosphere have increased levels of iononisation. However if the levels of ionisation in the lower elvels start to rise then this can result in higher levels of attenuation of the radio communications signals and poor conditions may be experienced. Additionally an increase in the level of background noise at VHF can also be detected easily.

Flares generally only last for about an hour, after which the surface of the Sun returns to normal although some Post Flare Loops remain for some time afterwards. The flares affect radio propagation and radio communications on Earth and the effects may be noticed for some time afterwards.

Solar Flare Classifications:   Flares are classified by their intensity at X-ray wavelengths, i.e. wavelengths between 1 - 8 Angstroms. The X-Ray intensity from the Sun is continually monitored by the National Oceanic and Atmospheric Administration (NOAA) using detectors on some of its satellites. Using this data it is possible to classify the flares. The largest flares are termed X-Class flares. M-Class flares are smaller, having a tenth the X-Ray intensity of the X-Class ones. C-Class flares then have a tenth the intensity of the M-Class ones.

It is found that the occurrence of these flares correlate well with the sunspot cycle, increasing in number towards the peak of the sunspot cycle.

CMEs

Coronal mass ejections, CMEs, are another form of disturbance that can affect radio communications. Although much greater than flares in many respects, CMEs were not discovered until spacecraft could observe the Sun from space. The reason for this is that Coronal Mass Ejections, CMEs can only be viewed by looking at the corona of the Sun, and until the space age this could only be achieved during an eclipse. As eclipses occur very infrequently and only last for a few minutes. Using a space craft the corona could be seen when viewing through a coronagraph, a specialised telescope with what is termed an occulting disk enabling it to cut out the main area of the Sun and only view the corona. This enabled the corona to be viewed.

Although ground based coronagraphs are available, they are only able to view the very bright innermost area of the corona. Space based ones are able to gain a very much better view of the corona extending out to very large distances from the Sun and in this way see far more of the activity in this region, and hence view CMEs.

Coronal Mass Ejections, CMEs are huge bubbles of gas that are threaded with magnetic field lines, and the bubbles are ejected over the space of several hours. For many years it was thought that solar flares were responsible for ejecting the masses of particles that gave rise to the auroral disturbances that are experienced on earth. Now it is understood that CMEs are the primary cause.

It is now understood that CMEs disrupt the steady flow of the solar wind producing a large increase in the flow. This may result in large disturbances that might strike the Earth if they leave the Sun in the direction of the Earth.

Coronal Mass Ejections, CMEs are often associated with solar flares eruptions but they can also occur on their own. Like solar flares their frequency varies according to the position in the sunspot cycle, peaking around the sunspot maximum, and falling around the minimum. At solar minimum there may be about one each week whilst at the peak two or three may be observed each day. Fortunately they do not all affect the Earth. Material is thrown out from the Sun in one general direction and only if this is on an intersecting trajectory will it affect the Earth.

CMEs can give rise to ionospheric storms. These can provide a short lived enhancement to ionospheric radio propagation conditions but before long this can result in a black out to radio communications via the ionosphere.

Coronal Holes

Coronal holes are another important feature of solar activity. They are regions where the corona appears dark. They were first discovered after X-ray telescopes were first launched into space and being above the Earth's atmosphere they were able to study the structure of the corona across the solar disc. Coronal holes are associated with "open" magnetic field lines and are often although not exclusively found at the Sun's poles. The high-speed solar wind is known to originate from them and this has an impact on ionospheric radio propagation conditions and hence on all HF radio communications.

Summary

Solar disturbances are responsible for many of the major changes in the ionosphere. The effects of both CMEs and solar flares can cause major changes to ionospheric radio propagation, often disrupting them for hours or sometimes days. As a result a knowledge of when they are happening, and their size can help in predicting what ionospheric radio conditions may be like.