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2012-05-01
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MAJOR CHANGES TO BELT INDEX CALCULATIONS (10/06/2004)
**** Note: All older files can still be found in the old_bi directory ****
**** The older files should be used with caution. Please read all the ****
**** README files in the old_bi directory before using those files. ****
We have recalculated belt indices for all NOAA-15 data since 2000 and for all
NOAA-16 data since 2002. Several changes have been made in the procedure for
doing these calculations that users should be aware of.
The file named bi_YYYY.txt is for the current year, and uses data from the
current primary POES satellite. All other files are named bi_NSS_YYYY.txt,
where 'SS' is the POES satellite number.
In the past we have updated all median sensor responses (that serve as the
reference for calculating belt indices) on a yearly basis and use that updated
reference set for the next year's processing. This was done to compensate for
the gradual degradation of the solid-state detectors in the proton telescope
systems. It has been pointed out by a user that while this might be
appropriate for the 30 keV to >6900 keV proton belt indices, changing the
reference obscures the year-to-year changes in the energetic electron and solar
proton radiation environment as tracked by the daily belt indices. The
solid-state detectors in the electron telescopes and in the omni-directional
detector systems are much less susceptible to radiation damage and there is
little need to update the median reference fluxes for these detectors.
Therefore, in the reprocessing we have used the NOAA-15, year 1999 electron and
solar proton median flux values for all subsequent years. For NOAA-16 we have
used the reference values from 2001 in a similar way. We continued to use
yearly updated reference fluxes for the calculation of the 30 keV to >6900 keV
proton belt indices.
A second change implemented in the reprocessing was to use the current year's
L-value data in sorting data into inner, slot, and outer zone regions. The
L-value set that had been used dated to 1995 and the secular change in the
geomagnetic field over time rendered that L-value set out of date.
A third change was to compute belt indices for all 22 energetic particle sensor
channels observed by the SEM-2 instrument. In the past belt indices had been
calculated only for observations from the horizon viewing (90-degree) detectors
and the 4 omni-directional detectors. At geographic latitudes above about 30
degrees, the zenith viewing detector systems sense particles in the atmospheric
loss cone. Because of this the count rates from the zenith viewing telescopes
are ordinarily low, although during periods of high activity those count rates
may become comparable with those from the horizon viewing detectors. At low
geographic latitudes, however, the role between horizon viewing and vertical
viewing telescopes is reversed. At these locations, the vertical viewing
detectors sense the trapped particle population and provide the better measure
of the radiation belt intensities. Primarily for this reason, but also
because the zenith viewing detectors track the radiation belt particle
population at higher latitudes, we have now computed daily belt indices for the
zenith viewing detectors as well.
Finally, we have implemented better data quality procedures in the
calculations.
These improvements have resulted in minor changes to the daily belt indices
calculated from the horizon viewing (90 degree) proton telescope data and from
the omni-directional detector data. The changes in the daily indices calculated
from the horizon viewing electron telescope data can be more substantial as the
reference fluxes are no longer updated. Also, belt indices from all 22
particle species and energy now appear in the listing.
*********************
Forma:
********************
The bi_YYY.txt files contain the foloowing data, delimited by one or
more spaces. (A Belt index value of -1.0000 signifies that the particle
count rate for that data channel was insignificant, i.e. less than 10 per
second.)
Day of month
Month number (1-12)
Year (4 digits)
Sensor number
Total Belt Index
Inner Belt Index
Slot Belt Index
Outer Belt Index
****************
SEM-2 Sensor Numbers
****************
**NOTE 05/02/2012 THE LABELS FOR THE INDICES
**HAVE BEEN CHANGED. THE PREVIOUS README HAD
**THE 0 DEGREE and 90 DEGREE DETECTORS LABELED INCORRECTLY
0 >30 keV Electrons (0 deg detector)
1 >30 keV Electrons (90 deg detector)
2 >100 keV Electrons (0 deg detector)
3 >100 keV Electrons (90 deg detector)
4 >300 keV Electrons (0 deg detector)
5 >300 keV Electrons (90 deg detector)
6 30-80 keV Protons (0 deg detector)
7 30-80 keV Protons (90 deg detector)
8 80-250 keV Protons (0 deg detector)
9 80-250 keV Protons (90 deg detector)
10 250-250 keV Protons (0 deg detector)
11 250-250 keV Protons (90 deg detector)
12 800-2500 keV Protons (0 deg detector)
13 800-2500 keV Protons (90 deg detector)
14 2500-6900 keV Protons (0 deg detector)
15 2500-6900 keV Protons (90 deg detector)
16 >6.9 MeV Protons (0 deg detector)
17 >6.9 MeV Protons (90 deg detector)
18 16-70 MeV Protons (Omnidirectional)
19 35-70 MeV Protons (Omnidirectional)
20 70-235 MeV Protons (Omnidirectional)
21 140-275 MeV Protons (Omnidirectional)