Courtesy of Dave Evans and Sue Greer of the NOAA Space Environment Center and Michael Golightly of NASA Johnson Space Center.
Red/Orange = Greater than Average
Yellow/Dark Blue = Average
Light Blue/White = Less than Average About the plot:
A quick glance at the plot tells you whether the satellite radiation environment is unusually high (red/orange), average (yellow/dark blue) or unusually low (light blue/white) today. The belt indices in the upper right hand corner (click on the plot for a larger version) give the ratio of the electron flux integrated over specific regions to the 1-year average for those same regions. These indices are a quick-look at how significant the radiation environment really is right now. The plot shows high-velocity electrons (energies > 30 keV) observed along the orbit of NOAA/TIROS at ~800 kilometers above the Earth's surface compared to the value at the same location averaged over the past year. The plot is broken up into lines because the satellite track does not cover all points above the Earth in a single day. The red box shows where the satellite was at the beginning of the day. The red triangle is its position at the end of the day's observations.
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Color Scale: Counts per Second
Red> 10,000
Deep Blue< 10About the plot:
This plot shows the averaged intensities of 30-1100 keV (1 keV=1000 electron volts) electrons using the last year of observations by NOAA/TIROS. Basic Features to Look for:
The red region of enhanced radiation over South America at the center of the map is called the South Atlantic Anomaly. This has been referred to as the Sargasso sea of satellite navigation. This perilous region, reaching a peak just off the coast of Brazil, results because the Earth's magnetic core is shifted from the center of the planet by about 500 kilometers. Because of this shift, the magnetic field is weaker over South America. Trapped radiation belt particles penetrate much deeper in the atmosphere here (within a few hundred kilometers of the surface) intersecting the paths of satellites in low-earth orbit, burying themselves in sensitive electronics and disrupting the onboard computers. Narrow yellow bands that stretch across the map at mid-latitudes (in the northern hemisphere, across the middle of the U.S. and, in the southern hemisphere, skimming the bottom of the South Atlantic Anamoly) are high-energy electrons from the outer radiation belts. They are separated by a narrow white region from thicker brighter yellow bands at higher latitude. These highest-latitude (brightest yellow) bands are electrons associated with the auroral oval. |
