SRI International, an independent nonprofit research institute, has announced that early scientific results are now available from the Advanced Modular Incoherent Scatter Radar (AMISR), a modular, transportable radar system funded by the National Science Foundation (NSF) that has recently completed the first two years of operation.
Scientists are using the novel system to investigate the interaction of upper atmospheric phenomena, which are driven by energetic particles and the solar wind that cause spectacular displays of the aurora borealis, with lower atmospheric phenomena such as tropospheric storms and weather patterns. Remote operation and electronic beam steering allows researchers to operate and position the radar beam instantaneously to accurately measure rapidly changing space weather events.
"The AMISR system is unique among upper atmospheric radars in that it is capable of observing small-scale and temporally dynamic phenomena such as the aurora and space weather storms. Scientists need to understand how the upper atmosphere behaves on these scales to adequately study climate change and other processes linked to the transfer of energy and momentum from the surface of the sun to Earth’s atmosphere," said Robert Robinson, AMISR program manager at NSF.
New Research Investigates Auroral Arcs and High-Altitude Clouds
A recent issue of the Journal of Atmospheric and Solar-Terrestrial Physics (JASTP) is dedicated to early research results from the Poker Flat, Alaska deployment of AMISR (known as PFISR).
The article, "Coordinated Optical and Radar Image Measurements of Noctilucent Clouds and Polar Mesospheric Summer Echoes," by Michael Taylor, Ph.D., professor at Utah State University, describes the first detailed investigation of the common horizontal and vertical structures of radar and optical mesospheric clouds. These are the highest altitude clouds, which form in the mesopause, the coldest part of the Earth’s atmosphere. These high-altitude clouds may be an indicator for global climate change since their increasing occurrence rate implies a cooling mesopause.
A second article, "Volumetric Imaging of the Ionosphere: Initial Results from the PFISR," by Joshua Semeter, Ph.D., associate professor at Boston University, presents the first three-dimensional images of the aurora borealis seen from PFISR. Volumetric imaging allows scientists to observe in three dimensions where and how magnetospheric energy is deposited into the system that couples the Earth’s ionosphere and upper atmosphere. Without this kind of detailed understanding, space weather models can not reproduce or predict future behavior.
Novel Radar is Dedicated Solely to the Research Community
NSF operates other large incoherent scatter radars, including ones located in Greenland, Peru, Puerto Rico, and Massachusetts. The SRI-designed AMISR is the first NSF-funded radar system that was developed and built specifically for scientific research.
NASA has used the array to determine the most optimal space weather conditions for launching scientific rockets. Since AMISR is capable of simultaneous monitoring in multiple directions, measurements can provide a multi-dimensional view of Earth’s upper atmosphere and ionosphere in real-time, providing a unique perspective for scientific rocket and satellite missions. AMISR is a significant technical advance from systems that provide one-dimensional measurements along a single trajectory.
AMISR also supported the International Polar Year (IPY), an international research program focusing on the polar regions of the world. Jan Sojka, Ph.D., professor at Utah State University, is one of many scientists who have requested experiment time on the new radar. His objective is to study how the ionosphere changes in response to energy input from above and below. He scheduled AMISR observations every 10 minutes for the entire IPY.
Sojka explained, "The year-long AMISR data set contained the information we needed to resolve long-standing questions about how the ionosphere responds to energy input associated with such phenomena as the aurora borealis and atmospheric waves and tides. Only AMISR has the necessary temporal and spatial resolution to study this very dynamic region of Earth’s atmosphere."
Initial results from Sojka’s work are detailed in the article, "The PFISR IPY Observations of Ionospheric Climate and Weather," also in the PFISR special issue.
AMISR began operating in January 2007. The AMISR system at Poker Flat was the first of three radars constructed by SRI. The next two radars are being constructed in Arctic Canada, at Resolute Bay in the territory of Nunavut. The first of the two radars will become operational later in 2009. These incoherent scatter radars are the closest in the world to the magnetic north pole (an important distinction when it comes to ionospheric and magnetospheric research) and provide unprecedented views of the complex physical processes that couple the sun, magnetosphere, and ionosphere.
"Because the very large AMISR system is configured in modules, the facility can be relocated for studying upper atmospheric activity around the globe," said John Kelly, Ph.D., director of SRI's Center for GeoSpace Studies. "In addition, each of the three antennae faces of the system can operate together or can be independently deployed in up to three separate locations. This facilitates comprehensive data gathering to increase our scientific understanding of upper atmospheric phenomena, which ultimately will help prevent the potentially large economic losses that can result from severe space weather events."
In addition to funding from NSF, several companies supported the SRI-led project. These include subcontractor Sanmina-SCI, which manufactured the Antenna Element Units, the basic building blocks of the radar panels. The Massachusetts Institute of Technology (MIT) served as the co-investigator on the project.
- Taylor et al. Coordinated optical and radar image measurements of noctilucent clouds and polar mesospheric summer echoes. Journal of Atmospheric and Solar-Terrestrial Physics, 2009; 71 (6-7): 675 DOI: 10.1016/j.jastp.2008.12.005
- Semeter et al. Volumetric imaging of the auroral ionosphere: Initial results from PFISR. Journal of Atmospheric and Solar-Terrestrial Physics, 2009; 71 (6-7): 738 DOI: 10.1016/j.jastp.2008.08.014
- Sojka et al. The PFISR IPY observations of ionospheric climate and weather. Journal of Atmospheric and Solar-Terrestrial Physics, 2009; 71 (6-7): 771 DOI: 10.1016/j.jastp.2009.01.001
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