Big Years for the Heliosphere

Svalbard ISR's Antennas
The 32 and 42-meter parabolic dish antennas of
the Svalbard incoherent scatter radar in Arctic
Norway are helping to compile an historic
2-year continuous record of charged particles
in Earth’s ionosphere. (Photo Courtesy EISCAT)

With electricity supplies limited and mean temperature stuck below freezing for 8 months a year, it’s no surprise that in years past the Svalbard radar station on Spitsbergen Island in Arctic Norway ran just a few days at a time. The 32 and 42-meter parabolic dish antennas and transmitter, an incoherent scatter radar or ISR for short, would take a sequence of snapshots of the charged particles in the ionosphere 80-500 kilometers above Earth’s surface before shutting down again for a week or so. That rendered it blind to the ionosphere’s longer-range dynamics, much as “someone living in a windowless building who walked outside only at midday each day would be unaware that the sun set below the horizon at night,” notes Tony van Eyken, director of EISCAT (for European Incoherent SCATter), the international operation that owns the Svalbard ISR.

Until March 1, 2007, that is. On that day, at 1700 UT, Svalbard began scanning the ionosphere round-the-clock to produce what van Eyken calls, “the most detailed and extensive record of the high latitude ionosphere ever recorded.” Within months the resulting dataset was already testing the best models of how the Sun, the Earth’s geomagnetic field and other influences impinge on the ionosphere and how the ionosphere, in turn, affects Earth’s climate. On February 29, 2008 the ISR will scale its continuous operation back to a biweekly scanning schedule that should continue to pick up long term variations that the earlier operations could not have seen.

The launch of Svalbard’s unprecedented run marked the start of International Polar Year (IPY). But it is just one of hundreds of projects pushing the bounds of science thanks to three such ‘international science years’ that got underway in 2007: IPY and International Heliophysical Year (which, in spite of their names, run for two years), and the 1.5-year long Electronic Geophysical Year. All three seek to extend the legacy of 1st and 2nd International Polar Year (125 and 75 years ago) and the 1st International Geophysical Year (50 years ago). These global extravaganzas reaffirmed international cooperation in science, inspired the treaty protecting Antarctica for peaceful uses and research, and made startling discoveries.

WHAT’S IN A YEAR FOR SCIENCE?

Svalbard’s run highlights the overlapping missions of the larger IPY effort and that of the heliosphysical and electronic geophysical years. Anyone lucky enough to have witnessed the auroras streaming down into the Earth’s polar regions can grasp the special connection between the poles and the heliosphere, which is the magnetic zone containing our solar system, the charged particles known as the solar wind, and the Sun’s magnetic field. The auroras are visual evidence that energetic solar particles penetrate Earth’s protective magnetic bubble at the poles. The objective of International Heliospherical Year (IHY) is to discover how such phenomena are coupled to the Earth and its climate.

Electronic Geophysical Year (eGY), meanwhile, seeks to make geophysical data as ‘open access’ as possible. That is an ideal heartily embraced by many IPY and IHY projects such as the Svalbard radar run which are producing virtual observatories to ensure that their observations will be studied as widely and as effectively as possible.

Sample targets for Heliosphere Impact on Geospace
– Weird “auroral precipitation” events in which energetic protons from the Sun unleash electrons in the stratosphere, producing activated nitrogen that contributes to ozone destruction
– Electron precipitation from Earth’s radiation belt and lightning between and within Earth’s ionosphere and magnetosphere
– Steep electron gradients in the ionosphere which distort GPS signals and disrupt communications networks

The practical impact of these science years is to inspire the extra funding and collaboration needed to understand highly complex and dynamic properties of the Earth. Svalbard’s project was approved for inclusion in the international science years as part of a broader program called Heliosphere Impact on Geospace, which includes another 28 international research projects led by scientists in Australia, Brazil, Canada, China, Finland, Italy, Japan, Malaysia, Norway, Russia, Sweden, U.K., Ukraine, and the U.S.

Inclusion in the science years often translates into expanded government funding for observational equipment. The UAMPY project coordinated by Professor Lucilla Alfonsi at the Istituto Nazionale di Geofisica e Vulcanologia in Rome is collaborating with another IPY called POLENET to build a dense network of Antarctic GPS-receivers. POLENET will use the GPS for meteorology, glaciology and seismology, while UAMPY will use them to model steep electron gradients in the ionosphere that cause scintillations in the GPS radio signals as they pass through, modeling that may ultimately improve the reliability of GPS.

In other cases science year funding and collaboration greases the gears to enable unprecedented coordination of existing observing instruments, be they on the ground, in the air or on satellites. Take the POGHEX project led by John Cooper, chief scientist at NASA Goddard Space Flight Center’s Space Physics Data Facility. POGHEX is using observational ‘campaigns’ to investigate the flow of cosmic ray energy from within the heliosphere, the Sun, and beyond. To cover this immense region the project is integrating observations by spacecraft, including the Voyager spacecraft now probing the outer reaches of the heliosphere, and from a circumpolar Antarctic flight of high-altitude balloons in December. (These balloons are better known to Earth observers as Balloon-borne Experiments with a Superconducting Spectrometer or BESS.)

ICESTAR Conjugancy Imaging
These synchronized images of auroras by satellites
over Earth’s north and south poles, assembled by a
Norwegian/U.S. project called ICESTAR, show
that events at one pole are not always mirrored at
the other. In the event shown, the aurora rising up
from the South Pole appears to displace
brightening in the north.
(Photo Courtesy Nicolai Østgaard)

The power of dataset integrations such as POGHEX was demonstrated recently by a U.S./Norwegian team involved in another Heliosphere Impact project called ICESTAR examining the coupling between the auroras in the North and South hemispheres. “This is about how energy flows into our system,” says Nicolai Østgaard, an expert in space physics at the University of Bergen. Until now most models have assumed that equal energy flows in to both polls and thus the events at one are mirrored at the other, essentially ignoring the tilt of the Earth which can put the poles at different angles from the sun. Østgaard and his colleagues showed that was a dangerous assumption in research published last year in the Journal of Atmospheric and Solar-Terrestrial Physics.

Østgaard’s team used simultaneous imaging by satellites above each pole, IMAGE and Polar at the Arctic and Antarctic, respectively, to demonstrate that this is a greater simplification than scientists have realized. They observed some phenomena, such as the theta aurora that stretch a luminous belt across the polar cap, occurring independently in one hemisphere as well as events where brightening in one hemisphere, such as the onset of a solar-induced substorm, displaced the brightening in the opposing hemisphere. In some cases the quantitative divergence from current models was as high as ten-fold. “Without funding from IPY we would not have been able to do this,” says Østgaard.

SETTING THE SIGHTS HIGH

The Svalbard ISR radar run is a subproject within ICESTAR combining campaign-level coordination of observatories and better use of existing equipment. Extra funding was required to provide continuous operation of the Svalbard ISR, the project’s backbone, which is no easy task inside the Arctic Circle. “Operating one of these radars in this way is a major undertaking and a dramatic change,” says van Eyken. “Prior to the IPY, the longest runs ever were little more than a month.”

Van Eyken says that once it became clear that Svalbard would run flat out for a year, ISR teams around the pole jumped in to support the effort. Radars at Millstone Hill near Boston and Sondrestromfjord in Greenland are making coordinated observations every two weeks, the Russian Radar at Irkutsk in Siberia plans to make four month-long observations, and a newly-installed ISR in Alaska is trying to match Svalbard’s round-the-clock operation. Van Eyken says the project is going very well so far: “All the radars have substantially achieved their targets, the data processing is up to date, and the results are freely distributed via the web.”

Anthony van Eyken at Svalbard
Anthony van Eyken, the man behind the machines
at the Svalbard radar on Spitsbergen Island in
Arctic Norway, carries a rifle for protection from
roaming polar bears, just one of many challenges
to the remote station’s historic 2-year run.
(Photo Courtesy Cesar La Hoz)

The greatest challenge to date for van Eyken has been glitches at the local coal-fired power plant (the only one in Norway) which feeds the ISR, the local village, and nearby mining operations, including the mines that supply coal to the station. “The radar accounts for a substantial fraction of the total load on the power station and technical problems there have meant that there has not always been enough power to run the radar and the village,” says van Eyken.

And the results? The ISR data shows that both the density and altitude of ionization in the upper atmosphere are very low, well beyond the levels that models would predict, even for the cyclical period of relatively low solar storm activity we are currently experiencing (known as a solar minimum). Van Eyken speculates that this may be the signature of cooling in the upper atmosphere, a link that has yet to be proven. “Such effects are predicted to occur with increases in greenhouse gases in the atmosphere but it is yet to be demonstrated that the two effects are actually related,” says van Eyken.

SHARING THE WEALTH

Researchers say the datasets pouring out of the science years are already stimulating friendly scientific dueling as modelers take the early data, feed it to their models, and generate predictions for future atmospheric developments that are tested against the incoming data. The results of one “ionosphere-thermosphere challenge” based on the continuous ISR data are posted on a wiki set up by Jan Sojka, a physicist at Utah State University. Van Eyken says such intense model-testing is an important step towards forecasting, which he calls “essential” to the ability to “handle the effects of space weather on our increasingly technologically dependent society.”

Van Eyken and the ISR community also exemplify another goal of IPY and IHY and the explicit function of eGY: encouraging open access to scientific data. One approach to this is creation of ‘virtual observatories’ which bring together disparate but related data sources. Generally they include systems to retrieve data, handle any format conversions required, and then provide a user interface to ease browsing or heavy-duty data-mining of the datasets. In the ISR case, John Holt, a principal scientist on the Millstone Hill ISR, is leading development of a virtual observatory called Madrigal to pull together the ISR observations.

Other virtual observatories emerging from this community include the Virtual Global Magnetic Observatory housed on University of Michigan servers (Vladimir Papitashvili from Michigan is on the IPY’s Data Management subcommittee), the University of Calgary-operated GAIA Virtual Observatory which provides access to 10 million summary images and keograms from all sky imagers, meridional scanning photometers, riometers, and satellite borne global imagers from a number of international sources, and the Virtual Cosmic Ray Observatory (ViCRO) proposed by NASA’s John Cooper to manage data from POGHEX and related experiments.

These observatories should ensure that the legacy of the three science years that got started last year will continue to grow for many years to come.

Topic: