3/2/00

The data directory for Belt Indices of Relative Intensities of NOAA/POES 
Energetic Particles is being developed and filled.  

Check this file for the latest information.

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Belt Indices:  Just as each orbital data "point" (2x5 degree box) in the 
"tiger plot" of Relative Intensities of NOAA/POES Energetic Particles 
displays a color-coded ratio of the particle count to a one-year average 
particle count, the belt indices are the ratio of the whole day's summed 
particle counts to their corresponding one-year summed average.  The 
indices are subdivided by the L-values of the points, resulting in three 
separate values, corresponding to:  inner (L-value < 2.0), slot (2.0 <= 
L-value < 2.5), and outer (L-value >= 2.5), and finally a total index 
which accounts for all points, without regard to L-value.  A particle 
count rate of less than 10 per second is considered insignificant even if 
it is above average.

A Word of Caution about Belt Indices and the Solar Cycle
--------------------------------------------------------

The belt indices are a measure of the integrated difference, or 
departure, of individual sensor responses observed on a given day from 
the responses of those sensors as averaged over the previous year's 
observations.   

It must be stressed that the one-year data averages, that form the basis 
for the comparisons and calculation of belt indices, are recalculated 
from time to time (about every three to six months) and do not represent 
observations from a fixed one-year interval, for example, solar minimum. 

This was done for two reasons.  First, several of the solid state 
detectors in the Space Environment Monitor experience normal radiation 
damage over time that reduces their sensitivity and make misleading a 
comparison of their current reponses with their responses early in their 
life, even for the same radiation environment.  Second, it was believed 
that most operational users were interested in the departure of the 
current radiation environment from the environment that the user's 
systems had normally experienced over the more recent past as opposed to 
the radiation environment many years ago. 

However, this procedure creates a loss of continuity in the meaning of 
the belt indices collected over a long period of time.  For example, as 
solar and geophysical activity increase it is expected that each update 
of one-year averages will display an increase in the averaged sensor 
responses.  This, in turn, will be reflected in a relative decrease in 
the magnitude of the belt indices because the daily sensor responses will 
be compared to averages that, themselves, are increasing in magnitude.  
Users of the belt indices, especially for long-term studies, should be 
aware of this aspect of these data. 


Data collection began in April 1997, and continues through yesterday.
However, the satellites and instruments have not been the same throughout.
From February 29, 2000 onward, the instrument has been SEM-2, which has
13 sensors for which belt indices have been calculated.  Prior to that, 
the instrument was SEM-1, which had only 11, and from December 1998 through
February 29, 2000, the satellite (NOAA-14) which provided the data, had
some sensors going bad, so only a subset of the sensors gave belt indices. 

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Format:
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The bi_YYYY.txt files contain the following 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 that 10 per 
second.)

Day of month 
Month number (1-12)
Year (4 digits)
Sensor number (90-deg and Omnidirectional sensors only -- see table below.)
Total Belt Index
Inner Belt Index
Slot Belt Index
Outer Belt Index

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SEM-2 Sensors:
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 1  >30 keV Electrons (90 deg detector)
 3  >100 keV Electrons (90 deg detector)
 5  >300 keV Electrons (90 deg detector)
 7  30-80 keV Protons (90 deg detector)
 9  80-250 keV Protons (90 deg detector)
11  250-800 keV Protons (90 deg detector)
13  800-2500 keV Protons (90 deg detector)
15  2500-6900 keV Protons (90-deg detector)       
17  >6.9 MeV Protons (90 deg detector)
18  16-70 MeV Protons (Omnidirectional)
20  35-70 MeV Protons (Omnidirectional)
21  70-235 MeV Protons (Omnidirectional)
22  140-275 MeV Protons (Omnidirectional)