Without the sun, life on Earth could not exist. As the sun rises and sets every day, it sustains a delicately balanced cycle for many of Earth's processes. At sunrise, human beings and other diurnal creatures awaken from slumber and commence their daily routines. When the sun sets, the diurnal return to their beds to rejuvenate for the next day while the nocturnal are waking up for breakfast. Our bodies depend on the sun's light to maintain these healthy circadian cycles. Sunlight also stimulates the brain's natural production of the mood-lifting chemical serotonin, and it helps our bodies produce vitamin D when it shines on our skin. During the day, the sun's rays allow plants and plankton to photo-synthesize, producing sugars, starches and oxygen to fuel all other life on Earth. Behind the sun's life-perpetuating brightness, however, is its dark capacity to disrupt or even destroy the very life that it so delicately sustains.
Although the sun seems harmless at a distance, it harnesses the potential to inflict serious damage on our planet. The sun is constantly blasting plasma - a sea of charged particles - in all directions into space at speeds of up to a million miles per hour or more. This plasma, known as the solar wind, bombards Earth with massive amounts of protons, electrons and ionized atoms that can pose a serious threat to life, as we know it. If these particles were free to hit the planet, the radiation would cause life-threatening injuries to our DNA, and the massive influx of charged particles would debilitate power grids, disrupt communications networks and damage all electronic devices.
Solar activity has a direct impact on environmental conditions in near-Earth space - a concept known as space weather. Solar wind is not the only sort of activity that can affect us here on Earth. Solar flares are explosive storms that occur on the surface of the sun. These flares can emit bursts of charged particles with energy comparable to 10 million volcanic eruptions. The sun also occasionally emits coronal mass ejections, or CMEs - powerful, enormous eruptions of plasma from inside the suns corona that are much more dangerous than solar wind or flares. CMEs can send up to 10 billion tons of the suns plasma surging into our solar system. When hot plasma from CMEs strikes our planet, it can produce extreme space-weather events called geomagnetic storms, and these storms can cause catastrophic damage to Earth and its technological systems.
Luckily, though, we have a natural defense against the constant attack from the sun - our magnetosphere. Earth's rapidly spinning metal core generates a magnetic field similar to that of an ordinary bar magnet. This magnetic field extends far into space - at least 37,000 miles (roughly 60,000 kilometres). Most charged particles cannot easily cross magnetic field lines. Instead, something called Lorentz forces, created by the earth's magnetic field, deflect the particles' paths. The magnetosphere therefore acts as an invisible shield around our planet, barring charged particles from plummeting through our atmosphere.
Despite its protective qualities, however, the magnetosphere also has vulnerabilities. Particles can still enter our magnetosphere by a process known as magnetic reconnection. Solar wind carries with it its own magnetic field, and when this magnetic field points in the opposite direction as Earth's magnetic field, the field lines connect in an explosive process that catapults charged particles into the magnetosphere. What's more, this is not the only way our magnetosphere can be infiltrated. Particles travelling along Earth's magnetic field lines at high enough speeds will penetrate our magnetosphere and enter the atmosphere through the north and south poles. Here the energetic particles interact with oxygen and nitrogen in the air to create aurorae - stunning, colourful ribbons of red, blue and green light that ebb and flow across the sky. These grand displays of light can usually only be seen at very high latitudes, but escalate in size and intensity with increases in solar activity. Intense solar storms may be beautiful to watch, but don't be fooled by this dazzling façade. The high influx of solar energetic particles from these storms can pose a serious hazard to life on Earth, disrupting power grids and communications networks while potentially exposing living things to harmful radiation.
Homa Karimabadi, group leader of space plasma simulations at the University of California, San Diego, has teamed up with visualization specialist Burlen Loring of Lawrence Berkeley National Laboratory (LBNL) to create a topological map of Earth's magnetosphere for global kinetic simulations, allowing them to closely study how space weather affects our magnetosphere. Homa Karimabadi and Burlen Loring worked with John Dorrelli, an expert on magnetospheric topological analysis of NASA's Goddard Space Center. "The 'topomap' helps us find the location of the magnetic field lines from different sources - for example, the magnetic field of Earth versus the magnetic field of the solar wind", explained Homa Karimabadi. Using NICS' supercomputing resources, they have become the first to create such a map to develop global kinetic simulations of the magnetosphere and space-weather effects. The team used Nautilus and Kraken to create their visualizations and simulations. A better understanding of how space weather affects our magnetosphere allows scientists to more accurately predict the impact of solar activity on our planet. With improved predictive capabilities, we can more effectively prepare for space-weather events.
"Earth's magnetic field provides a protective cocoon, but it breaks during strong solar storms", explained Homa Karimabadi. These storms, also known as geomagnetic storms, can cause massive power outages, disrupt communications and navigation systems, damage Earth's satellites and induce corrosive electrical currents through gas and oil pipelines. During periods of intense geomagnetic storms, flights must be rerouted around Earth's magnetic poles to avoid the dangers of exposing staff and passengers to high levels of radiation. Astronauts especially are at risk of exposure to unhealthy or even lethal amounts of radiation, even when they are inside their spacecraft.
Because the sun can eject plasma in any random direction, the odds of a serious CME being aimed directly toward Earth are slim. However, the risks posed by dangerous space weather are not to be taken lightly. In 1989, a series of CMEs and solar flares caused a severe geomagnetic storm that left millions of people in Quebec without power for more than nine hours. Blackouts spread south across America's north-eastern coast. This geomagnetic storm was so intense that the northern lights, which are normally only visible in parts of Canada, could be seen as far south as Florida. An earlier storm in 1859 known as the Carrington event was even more intense, creating auroras farther south than the Tropic of Cancer. Telegraph services experienced serious disruptions; random unreadable messages were coming through their instruments, and some operators even reported experiencing electrical fireworks sparking from their equipment.
CMEs pose a significantly greater risk to Earth than other potentially dangerous astronomical events. The likelihood of the sun emitting a CME depends on an 11-year solar cycle. During the peak of the solar cycle, the sun can emit several of them every day. At the minimum of the solar cycle, the sun may radiate only a couple per week. In the last 200 years, our planet has already experienced two geomagnetic storms intense enough to cost us billions, even trillions of dollars. "There is an estimated 12-percent chance in the next 10 years of a solar storm of the magnitude of the 1859 Solar Superstorm hitting Earth", stated Homa Karimabadi. "That would cause over $2 trillion in damage." This amount is equivalent to a whopping 30 times the amount of damage caused by Hurricane Sandy in 2012, which cost the United States roughly $65 billion.
As our world becomes increasingly dependent on electricity, we also become more and more vulnerable to the consequences of severe geomagnetic storms. A storm that merely disrupted telegraph services 150 years ago would do a whole lot more damage today. "Imagine having no power and communication for over three to six months and over large regions of the United States. We are simply not prepared to deal with such a calamity", stated Homa Karimabadi.
"There is an urgent need to develop accurate forecasting models. A severe space-weather effect can have dire financial and national-security consequences, and can disrupt our everyday lives on a scale that has never been experienced by humanity before", Homa Karimabadi explained. A geometric storm on the magnitude of the 1859 superstorm narrowly missed our planet in July of 2012. If this particular CME had occurred a few days sooner, our planet would have suffered devastating consequences. Entire nations could be left without power for weeks if such a storm were to happen again.
Although we have the capability to track solar activity, we do not yet have the proper tools to forecast the intensity of incoming storms. Simulations created by Homa Karimabadi's team should give scientists a clearer picture of exactly what happens in our magnetosphere during space-weather events. These simulations are very computationally intensive and involve a tremendous amount of data. Some run on up to 100,000 central processing units and take 48 hours or more to complete. "Handling and analysis of massive datasets resulting from our simulations are quite challenging. Partnering with the (visualizations) group at LBNL has been critical in developing tools to analyze our data sets", stated Homa Karimabadi.
To make sense of the vast amount of highly complex data, Burlen Loring and Homa Karimabadi's team have developed visualization techniques designed specifically for magnetospheric simulations. "Computing the maps is in itself a challenging computational problem", stated Burlen Loring. "We developed efficient parallel algorithms for computing these maps that allowed us to take advantage of NICS HPC resources. With our new algorithms and access to NICS supercomputing resources, the computation time dropped from a few days down to a few seconds."
Some of their simulations display Earth wrapped in a tangled mess of what one could easily mistake for green and yellow spaghetti. These twisted "spaghetti noodles", which are actually just magnetic field lines, demonstrate how the magnetic fields of Earth and the sun mingle. "By colour-coding the magnetic field from different sources, we can then see how they evolve in time and where they mix", stated Homa Karimabadi. "Said simply, regions where the field lines of different colours meet can be thought of (as) regions where the plasma from the solar wind penetrates Earth's magnetosphere."
Homa Karimabadi and Burlen Loring have also assisted teams working on the design and planning of NASA's Magnetospheric Multiscale (MMS) mission. In October of 2014, NASA's Solar Terrestrial Probes programme plans to launch four identical spacecraft to orbit Earth. These spacecraft will take measurements of magnetospheric boundaries and examine space-plasma processes such as energetic-particle acceleration, turbulence and magnetic reconnection. Their sensors will specifically measure charged-particle velocities and the magnitude and direction of electric and magnetic fields. The mission will provide very detailed measurements and establish new knowledge about the magnetosphere that will greatly help improve our space-weather forecasting capabilities.
Burlen Loring and Homa Karimabadi's team plan to continue to push the state of the art in simulations, theory and visualization to develop more detailed and accurate global models for space-weather forecasting. It is only a matter of time before another Carrington event strikes our planet. Better forecasting models are essential if we are to be prepared for space weather's most harmful effects.