On a "normal" day, the sun shines and rain falls on the earth. Winds blow according to a diurnal schedule, but interplanetary space also has normal days. Electromagnetically charged particles constantly flow out from the sun toward all planets. This wind is essentially "exhaust" from fusion, the violent thermonuclear engine of our star that converts hydrogen to helium at such an extraordinary rate, it is difficult to comprehend. Every second, 620 million metric tons of hydrogen fuses together, releasing 400 Septillion (4 X 1026) watts of energy. This energy comes in steady flows and in bursts.
The surface of the sun is magnetically complex, which lends to periods of instability. In general, the solar sphere is homogenously composed with intense nuclear energy production near the center at a temperature of more than 15 million degrees Kelvin. Near the sun's surface is a bubbling cauldron, the photosphere- not nearly as homogeneous as the deeper 90%. Pressure at the sun's center keeps all aspects of the inferno in place. But up at the threshold of space, physical quantities become much less stable. Magnetic fields tend to polarize and regionalize. Flows of solar plasma on and near the surface may become chaotic, further segregating opposed values of mass, magnetism and momentum. These areas are easily observed as sunspots, filaments and flares.
Solar physicists and space weather forecasters have developed elaborate methods of monitoring every aspect of the sun. From a number of locations around the world, the sun can be observed and analyzed 24 hours a day. On occasion, building stresses of magnetic polarity reach critical intensity. Just as electric polarity during thunderstorms eventually cause lightning bolts to satisfy equilibrium and return to stability, so too magnetic polarity can become so intense that the sun's surface literally explodes. A sunspot region breaches at the magnetic membrane and inconceivable amounts of energy are propelled into space. Shock waves reverberate across the solar disk with force easily able to obliterate the earth in an instant, if we were nearby. In addition to nuclear exhaust, many complex solar physical agents spew away from the surface- protons, electrons, x-rays, gamma rays and a whole host of electromagnetic ejecta. These charged particles are thrown out of the sun at tremendous speeds. The entire heliosphere bows outward taking the corona with it is spectacular fashion. They are called "Coronal Mass Ejections" (CMEs). When a CME shoots outward from the sun it may or may not be directed at earth. Most CMEs are not. But from time to time they are squarely aimed earthward.
The earth must then reconcile intense bombardment of charged particles, affecting the magnetosphere, and can result in mild disruption of the earth's magnetic field or a catastrophic geomagnetic storm of colossal proportion. These impacts have global reach, unlike other weather events. While most CMEs aren't extreme, some have become epic in the past, and certainly will be again in the future. Society has endured a few intense hurricanes, earthquakes and tsunamis (and solar flares). However, they will happen again- it is only a matter of when.
A notable difference between terrestrial natural disasters and space weather natural disasters is that a Katrina style CME has NEVER occurred during the technological age. Consequences of an extreme event can only be estimated. In 1989, the earth was struck by a severe CME in which an extreme geomagnetic storm developed, knocking out the electric grid in Quebec and parts of northeastern America- affecting millions. It took more than a year to repair all the damage. But in September 1859, the strongest geomagnetic storm in 500 years enveloped our planet. This event, renowned as the "Great Solar Tempest" and also known as the Carrington Event, was many times more severe than the 1989 Quebec storm. Spectacular auroral displays were observed worldwide, even to the equator.
Telegraphy had only been in existence for about 20 years in the civilized world. Telegraph lines shorted out causing numerous wildfires around the world, baffling scientists. With today's absolute reliance on modern technology, it is hard to specify know what would happen if an "1859-class" geomagnetic storm occurred. But this is certain- it would be catastrophic. The National Academy of Sciences in a 2009 report estimated trillions of dollars damage would occur requiring 10 years to repair.
Electric grid failure might be the least of our many problems. Satellite systems would be destroyed. Internet, I-Phone, and navigational system could not survive. Charging of metal pipes in the ground would have dangerous side effects. National security and military systems would be placed in jeopardy. International banking would be halted. Commercial aviation and general transportation would cease. Even our cars would not work. And this is just the tip of the iceberg. We are utterly dependent on modern technology. As you read this, look around and consider what would cease to operate if an 1859-class Geostorm were to hit in 2012. Your bedroom rug would survive, but what else? It could resemble a "Twilight Zone" episode.
How about people? Would we be OK? Most likely, yes. However, the magnetic field that protects our planet from such things could be temporarily damaged, with dangerous radiation reaching many parts of the earth. How then can mankind prepare for something like this? It is a critical question, the answer of which may hold our society's fate in the balance.
The blazing sun has power to drastically alter the human race. Should another 1859-class flare occur (or stronger), modern society would be at its mercy. Have you developed a contingency plan to survive in a world thrown back from the 21st century to pre-19th century sensibilities. What life was like before before modern technology may be enjoyable to read about or watch in movies. But the horrors we witnessed on 9-11 would not compare with the societal confusion and ultimate violence that would be born out of such an unfamiliar turn of events. Most people don't know how flipping a light switch on or off really works, so too few people appreciate the omnipotence of the sun and how a geomagnetic storm could essential end life as we know it on earth- with almost no warning. It gives one pause.