CLOUDY, WITH A CHANCE OF PROTONS: Solar storms caused by solar flares and coronal mass ejections (CMEs) generate charged particles that can pelt the Earth's magnetic field, interrupting communications and other electrical systems. Scientists are trying to better forecast space weather with the help of improvements to Iridium's satellite constellation. Image: COURTESY OF IRIDIUM
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The sun is a tempestuous place prone to proton and electron particle storms that can speed across a 150-million-kilometer space chasm to bash into Earth's atmosphere, potentially disrupting satellite service, damaging telecommunications networks, causing power grid blackouts and endangering high-altitude aircraft as well as astronauts on board the International Space Station. With the cycle of solar storms set to peak in the next three to five years, scientists at the Johns Hopkins University Applied Physics Laboratory (APL) are searching for ways to gather and analyze information that will enable them to forecast severe solar storms.
Solar storms are caused by solar flares and coronal mass ejections (CMEs) that generate charged particles, which can pelt the Earth's magnetic field if they are thrust in that direction. Much of the solar storm information that APL scientists seek to analyze comes from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE), a $4-million National Science Foundation–funded program that APL initiated in June 2008 along with The Boeing Co. and Iridium Communications to monitor magnetic-field disruptions in Earth's upper atmosphere. At the core of AMPERE is a communications network with 66 Iridium satellites, each of which has a magnetometer capable of monitoring Earth's magnetic field.
Iridium's satellites (pdf) operate in near-circular low Earth orbits (LEO) about 780 kilometers above the surface, traveling at about 27,000 kilometers per hour and circling the planet in about 100 minutes. There are 11 satellites in each of six orbital planes and their paths intersect roughly over the North and South poles.
With the proliferation of satellite-based communications that enable global positioning systems (GPS) as well as certain Internet, television and phone services in the past few decades, "we're more reliant on space technology now than we ever were before," says APL scientist and principal AMPERE investigator Brian Anderson. "My suspicion is that in this [upcoming] cycle of solar activity we will learn something about how sensitive we really are."
Solar storms can at times create radiation damage or introduce errors in satellite or spacecraft computer processors, causing them to function unpredictably, malfunction (sometimes permanently) or "misbehave" in other ways, Anderson says, adding that much of this activity goes unreported to the public because, particularly in commercial space-based systems, operators tend to be very reticent to admit they have had a problem that might discourage investors. Creating the ability to more quickly and accurately forecast space weather would give satellite operations teams, space programs and others technologies that rely on assets in Earth's space environment the ability to reposition satellites and/or shut down noncritical components as well as defer critical operations—such as uploading new software or orbital maneuvers—that might be adversely affected by storm effects, such as increased penetrating radiation.
CMEs leave the sun at speeds ranging from 20 to 2,000 or more kilometers per second. Estimating their arrival time at Earth's ionosphere is difficult because their speed changes due to interaction with the solar wind, a stream of electrically charged gas blowing continuously from the sun at about 400 kilometers per second. Light, x-rays and the CMEs themselves can reach the atmosphere anywhere between a few minutes and a few days after a solar outburst.
AMPERE took a major step toward real-time measurements in August when Boeing created a new data pathway for transferring AMPERE magnetic field samples from Iridium's satellites at a rate of every two to 20 seconds. Previous sampling, which took place every 200 seconds or so, was not frequent enough to capture information about solar storm–induced electric currents flowing into and out of the ionosphere, including the location and strength of these currents and their impact on Earth's magnetic field, Anderson says.
Electric currents that flow into and out of the ionosphere, which AMPERE monitors, have various effects on it as well as the atmosphere in general that can cause problems with tracking LEO space debris, the use of GPS systems, and even terrestrial power plants—as was the case when a geomagnetic storm took down Quebec's power grid in 1989, Anderson says, adding, "The operators didn't know what was happening." One of AMPERE's goals is to be able to issue advance alerts to such critical operations about when they may be impacted by solar storms.
With data coming in at closer to real-time intervals, "AMPERE will allow us to see geomagnetic storms and their effects on the Earth as far as energy deposition in the atmosphere," Anderson says. "We've never had an asset that allowed us to measure any fundamental electrodynamic quantity, current or electric field through the entirety of a geomagnetic storm and see what happens." The ability to gather more information more frequently is "a bit like having a new telescope that finally lets you see things you've never seen before," he adds.
AMPERE already shares information with the National Oceanic and Atmospheric Administration (NOAA) Space Weather Prediction Center, and Iridium's next-generation satellite network—called, appropriately, Iridium NEXT—is expected to work more closely with NOAA, NASA and other government entities. Each of the 72 NEXT satellites placed in orbit beginning in 2015 will be built with the capacity to carry sensors from NOAA and other groups into orbit so as to provide real-time, two-way communication.
Slide Show: Satellite Network Preps for Stormy Space Weather