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SXI - providing snapshots and movies
of the sun
for solar forecasters
by Barb McGehan
"This is the first instrument of its kind flown by NOAA and the first of its kind flown by any organization for routine space weather forecasting operations."
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First official image from the Solar X-ray imager taken during on-orbit test. |
NOAA's latest tool to help solar forecasters predict space weather is the Solar X-ray Imager (SXI), which is now sending real-time images of the sun to NOAA's Space Environment Center (SEC) in Boulder, Colo. Perched aboard the nation's newest environmental satellite, GOES-12, SXI will enable scientists to detect solar storms that could impact billions of dollars worth of resources in space and on the ground.
The instrument takes a full-disk image of the sun's atmosphere once every minute, and then SEC makes it available to both NOAA and the US Air Force. The information helps space weather forecasters to be more accurate in their predictions of stormy space weather conditions that can affect radio navigation, power networks and satellite communication systems.
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GOES 12, with its SXI, is lifted into orbit. |
SXI was launched on July 23, 2001 on NOAA's GOES-12 satellite. Now that the satellite has become operational, this instrument will provide routine, nearly uninterrupted full-disk, soft X-ray images and movies of the sun's outer atmosphere or corona. According to Steve Hill, project scientist, "This is the first instrument of its kind flown by NOAA and the first of its kind flown by any organization for routine space weather forecasting operations."
For over 20 years, scientists have realized that observing the corona was the key to monitoring and predicting solar-geophysical activity. This realization prompted NOAA in partnership with the US Air Force and NASA to propose, fund, develop, build and fly the operational solar X-ray telescope to support the operational space weather missions of NOAA and the USAF.
SXI is a small telescope that makes use of advanced technology and grazing incidence optics that allow it to see the sun's outer atmosphere or corona in X-rays," Hill said. "It permits solar forecasters to see phenomena they couldn't otherwise - such as coronal holes - whose high-speed winds lead to geomagnetic storms, and to infer solar activity occurring behind the sun's edge, or limb. X-ray images are also more accurate than white light imagers for identifying the location of flares."
A critical element of the mission of the NOAA Space Environment Center (SEC) is to monitor and predict space weather phenomena in order to help minimize their impacts on human activities. The SXI will be a useful tool to enhance many aspects of these services. In particular the main goals of the SXI instrument are to help NOAA's SEC improve the ability to predict solar flares; detect coronal changes that are indicative of a coronal mass ejection; observe solar coronal holes; support prediction of energetic particle events by pinpointing the location of major solar flares; and monitor the distribution of coronal emissions.
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Automated algorithms pin-point flare locations in real-time. |
In the last 25 years, there has been a substantial increase in the observations and understanding of the origin of coronal mass ejections. These events spew tons of solar gases, charged particles, and plasma into space. It is now understood that these coronal mass ejections, and their interaction with the solar wind are among the drivers for geomagnetic disturbances here at Earth. Space forecasters say that observations of the sun's corona during coronal mass ejections has shown that there are often indicators of the coronal mass ejections that are visible in soft X-rays. This information can assist forecasters in being more precise and accurate.
Particle events are another important phenomena that can affect satellites and high-flying aircraft, as well as navigation systems. The location of a major solar flare has a significant influence on the nature of any associated energetic particle event. The importance of this measurement has long been recognized and NASA, the US Air Force and other agencies have undertaken efforts to support worldwide, ground-based flare patrol for this purpose. However, with the realization that solar X-ray emission is really the dominant component of flare emissions, and the practical issue that ground-based observatories are subject to the limitations of adverse weather, the value of having continuous, minute-by-minute observations of X-ray emission on a geosynchronous spacecraft has become evident.
Hill says, "The SXI will enable up-to-the-minute images and series of images to be displayed in the operational forecast centers, assisting space weather forecasters in directly observing the phenomena as it occurs." This continuous watch and review by the forecast centers will support many existing space weather products including flare alerts and proton event warnings.
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The Space Environment Center provides real-time monitoring and forecasting of solar and geophysical events, conducts research in solar-terrestrial physics, and develops techniques for forecasting solar and geophysical disturbances. SEC's Space Weather Operations Center is jointly operated by NOAA and the U.S. Air Force and is the national and world warning center for disturbances that can affect people and equipment working in the space environment. |
[1/27/03]
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