Auroral Radar Network Expansion for Space Weather Forecasting to be Completed This Year
March 13, 2013
Surrounded by rolling hills with grazing cattle, Dartmouth engineering professor Simon Shepherd recently signed a lease for 20 acres on the island of Graciosa, Azores. This spring, he will return to the site in this autonomous region of Portugal to build two ground-based radars to help predict the effects of solar disturbances in outer space on Earth. This phenomenon, known as space weather, is caused by massive sun explosions called coronal mass ejections that can ultimately interrupt satellite communications and take out entire power grids.
The Azores radars are the final two of eight built by Shepherd and his former fellow postdocs under Dr. Raymond Greenwald at the Johns Hopkins University Applied Physics Laboratory with a $6 million grant from the National Science Foundation. Greenwald, who earned his Ph.D. in physics from Dartmouth in 1970, pioneered the technique and design of these radars, known as the Super Dual Auroral Radar Network, or SuperDARN. Today, an international SuperDARN team of 100 scientists has built and installed 30 ground-based radars in the northern and southern hemispheres—including those built by Shepherd and the group in Kansas, the Aleutian Islands, Oregon, and soon, the Azores—to measure the motion of the matter that fills 99 percent of outer space, known as plasma.
“This final build could take a month or longer, and it will likely occur in phases. I am hoping that we can begin construction this spring and finish by this summer,” says Shepherd, who fabricated the components of the radars at Thayer School. “My colleagues will send students, postdocs and scientists to help during the build, and I am also hoping to involve Dartmouth engineering students in the build as well.”
Once the radars are constructed, Shepherd will monitor the 24-hour radar data from his office at Dartmouth. The radar measures drifts of plasma within an electrically conducting layer in Earth’s atmosphere called the ionosphere, which facilitates the propagation of radiowaves for long distances.
"The frequency of the return signal is Doppler-shifted according the speed of the plasma, so we can measure the motion of the plasma over a very large area," says Shepherd. "The system works similar to a weather Doppler radar except that we use a lower frequency, the radio waves travel farther, and they reflect off different plasma rather than rain, snow or sleet."
The Azores radars, which Shepherd will visit yearly to maintain, are aimed to make observations in the polar regions where converging magnetic fields focus the effects of coupling to the solar wind most strongly.
“There has been even more collective excitement than usual about the Azores radars from the start of the project, and we are excited to get them up,” says Shepherd.
Below is a time-lapse video of the construction of two SuperDARN radar arrays in Oregon, led by Professor Shepherd: