NAME

USAGE

DESCRIPTION

niprelflarecalc calculates a metric or index that aids in identifying precipitating electron events in NICER data.

Precipitating electrons are detected when a reconnection or electron scattering event occurs in the earth's magnetosphere, which causes electrons to flow to NICER's orbital location. Unlike trapped charges, precipitating electrons are not trapped, and will likely end their lives when they reach the earth's atmosphere just below NICER's orbit.

Precipitating electrons that NICER detects are largely low energy (<20 keV) and enter through NICERs optical pathway like X-rays do. They are difficult to predict because they do not produce large numbers of high energy charge depositions (>20 keV), which are recorded as overshoot events. Precipitation events tend to occur in the polar horn regions, are highly variable, and can produce very high count rates, hence the name "flares."

Instead of modeling precipitation events as background, the NICER team currently recommends to screen them out.

To do this, the worflow consists of two parts.

• Calculate flare index. This task will calculate a column (default PREL_FLARE_INDEX) which indicates the likelihood of a flare occuring at each point in time.
• Calculate GTI. The niprelflaregti task can calculate a GTI from the index and other parameters, which excludes a large fraction of precipitation events.

It is unlikely the user will need to run this task. Instead they can run the standard tools nicerl2/niprefilter2/nimaketime, which creates the recommended columns and applies the recommended screening.

In addition to the flare index, niprelflarecalc can also calculate an estimated flare intensity. This value can be saved in a column designated by the prelctcol parameter, PREL_FLARE_EST by default.

PARAMETERS

infile = "" [string]

File name of input filter (MKF) file

outfile = "INFILE" [string]

File name of output filter (MKF) file, or INFILE to modify the input file in place.

(prelcol="PREL_FLARE_INDEX") [string]

Name of the output column for index. It will be created if it is not created already.

(prelctcol="PREL_FLARE_EST") [string]

Name of the output column for flare intensity estimate. It will be created if it is not created already.

(cor_shift=1.3) [real]

Amount to shift COR_SAX by when creating index. Internal parameter not recommended to change.

(trumpfact=65.0) [real]

Nominal ratio of overshoots to "trumpet rejected" counts, when not affected by precipitation flares. Internal parameter not recommended to change.

(cor_efold=0.2895) [real]

E-folding scale for COR_SAX when computing weighted flaring index. Internal parameter not recommended to change.

(niter=4) [int]

Number of iterations to perform when computing the index. A larger number takes longer time to compute and brings up fainter variability, but also averages over more timescales and may create enhanced edge effects at the edges of GTIs.

(cleanup="YES") [boolean]

If yes, then clean up temporary files. If no, temporary files remain. This is typically for debugging.

(clobber = NO) [boolean]

If the output file already exists, then setting "clobber = yes" will cause it to be overwritten.

(chatter = 2) [integer, 0 - 5]

Controls the amount of informative text written to standard output.

EXAMPLES

Computes the flaring index for filter file ni1234567890.mkf.

     niprelflarecalc n1234567890.mkf INFILE clobber=YES

SEE ALSO

nicerl2

niprefilter2

nimaketime

niprelflaregti

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