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2007-02-26
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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.
*************************************************************************
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.
**********
Format:
**********
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
**************
SEM-2 Sensors:
**************
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)