Array in East Antarctica to monitor space weather symmetry between polar regions
Posted September 27, 2013
When solar wind lashes the Earth’s upper atmosphere, the polar regions react with a brilliant light show known as auroras. The visible but ephemeral bruising of the planet’s magnetosphere by charged particles streaming from the sun is but one of many space weather phenomena that researchers are eager to learn more about.
The interest is more than academic. Solar storms, including coronal mass ejections, can affect everything from GPS signals to radio communications to power grids. How the solar wind interacts simultaneously with the magnetosphere and ionosphere at the Earth’s high latitudes is one question that remains unanswered.
“There may be a lot of asymmetry,” noted Hyomin Kim, a post-doctoral associate in Virginia Tech’s Center for Space Science and Engineering Research under Robert Clauer . A professor at Virginia Tech, Clauer is the principal investigator on a project to install a string of instruments in remote East Antarctica to collect data about space weather.
“One of the major goals is to look at the response to solar wind simultaneously in both hemispheres,” said Kim, leader of the Virginia Tech field team during the 2012-13 summer based at the U.S. Antarctic Program’s South Pole Station .
A robust space weather network overseen by the Technical University of Denmark already exists in Greenland along the 40° magnetic meridian, an imaginary line than runs between the north and south magnetic poles. Instruments designed to measure the response of the upper atmosphere to solar wind are far sparser in Antarctica.
“Antarctica is not an easy place to go. Now we’re putting out more instruments so we can monitor inter-hemispheric response to solar wind,” Kim said shortly after his team arrived at the South Pole to conduct repairs and installations of the equipment.
The somewhat unwieldy name of autonomous adaptive low-power instrument platform (AAL-PIP) belies the efficient nature of the mobile observatories, which can operate up to three years without a service call. That’s an important feature when sites are located hundreds of kilometers across the high polar plateau.
“Instead of just knowing what’s going on in the middle of Antarctica, and assuming that’s similar to what’s going on across the continent, we’re spreading things out and trying to build this grid,” explained Chad Fish of Utah State University who is on sabbatical at Virginia Tech.
The platforms sport two different kinds of magnetometers, a high-tech GPS receiver and a high-frequency radio – all contained in a super insulated box about the size of a foot locker. The instruments draw about 20 watts of electricity in the summer and eke by at 3 watts in the winter. Power comes from lead acid batteries charged by solar panels mounted on a tower. The instrument box and battery box are both buried below the snow surface.
The magnetometers collect data on the Earth’s magnetic field. The GPS is not intended for positioning, according to Adam Reynolds, an engineer with Boulder, Colo.-based Atmospheric & Space Technology Research Associates , which developed and built the GPS receiver with Cornell University and University of Texas at Austin.
Instead, the Connected Autonomous Space Environment Sensors (CASES) GPS receiver measures the total electron content of the ionosphere and ionospheric scintillations. The former measurement provides information about the ionosphere over a specific location, while scintillation is a measure of how rapidly the ionosphere is fluctuating between the receiver and satellite.
"Rapid fluctuations in the ionosphere caused by atmospheric storms can distort GPS signals. These fluctuations can disrupt communications and affect navigation receivers. The CASES receiver detects what’s going on in the ionosphere to let us know how other GPS receivers might be affected,” Reynolds explained.
The Virginia Tech array is one project of a larger, international program called Polar Experiment Network for Geospace Upper-atmosphere Investigations, or PENGUIn. PENGUIn investigators are after the big picture of how energy from the solar wind is transferred to the upper atmosphere at very high latitudes.
Solar wind is composed almost entirely of electrons and protons. The magnetic, comet-shaped cavity carved out of the solar wind by virtue of the magnetic field surrounding Earth is called the magnetosphere. The ionosphere forms the inner edge of the magnetosphere. The ionosphere is important, in part, because it influences high-frequency radio waves to distant parts of the planet.
Understanding what happens 90 kilometers above the Earth will eventually lead to better space weather models, not unlike the weather models that can forecast thunderstorms and hurricanes.
Zhonghua Xu, a post-doctoral associate at Virginia Tech, said increasing the number of observations around Antarctica is an important first step toward such a goal. A number of countries with research stations on the continent, including his native China, are bringing such a model closer to reality. The next challenge will be to synthesize all that data.
“We need to pull everything together,” he said.
NSF-funded research in this story: Calvin Robert Clauer and Brent Ledvina, Virginia Tech, Award No. 0839858 ; Calvin Robert Clauer, Tamal Bose, Joseph Baker, Brent Ledvina and Majid Manteghi, Virginia Tech, Award No. 0922979 ; and Calvin Robert Clauer, Virginia Tech, Award No. 0636691 .