The same Iridium satellites used by businesses to transmit data around the world have been tuned to provide comprehensive electromagnetic data about solar storms that will result in an early warning system to protect power grids.
By turning up the rate at which 66 satellites sample the magnetic field they are experiencing, Iridium can provide scientists with a wealth of new information about solar outbursts, such as the Aug. 1 coronal mass ejection that created spectacular borealis lightshows three days later on Earth.
The new capability is part of cooperative research among The Johns Hopkins University, Iridium and Boeing that is funded by the National Science Foundation and called Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE).
One of the benefits of the data will be predictions of when and where electromagnetic currents will pose a threat to commercial power networks by heating up transformers and generators, says Brian Anderson, principal AMPERE investigator at Johns Hopkins' Applied Physics Laboratory. (See also: Solar storms are more than a curiosity)
It can also show where the currents might affect navigation gear by disrupting GPS satellites, Anderson says.
The satellites normally sample the electromagnetic field every three minutes as part of the satellites' attitude control system. They use a three-axis magnetometer to help keep them stable and to point antennas in the right direction, says Ken Rock, the project manager for AMPERE at Boeing.
Strong bursts of electromagnetic radiation thrown off by the sun flow through the Earth's atmosphere creating magnetic fields of their own, registering fluctuations on the magnetometers. By using a model of what the Earth's magnetic field is, the satellites can subtract that value from the actual measurements made by the satellites to keep the satellites aligned properly, he says.
But the raw data is valuable to scientists who track solar flares and the electromagnetic storms they create on Earth. A software upgrade beamed to the satellites enables sampling the magnetic field as often as every 2.16 seconds, Rock says. The data is available to researchers about four minutes after it is gathered, he says.
At the request of Johns Hopkins researchers, the satellites gathered data at that rate during the storm that resulted from the Aug. 1 solar disturbance. The disruption created currents as far from the Earth's poles as the 40th parallel of latitude. Normally the activity occurs between the poles and the 70th parallel, Rock says.
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