1. Analyzing a Flare with Different Attenuator States

During most strong flares, the attenuator state will be changed. The following plot is an uncorrected quicklook light curve of the X4.8 flare on July 23 2002 plotted in the GUI.

As indicated by the purple horizontal bars, before 00:26:00 UT, the attenuator state was A1 (thin in). From 00:26:00 UT to 00:59:24 UT, the attenuator state was mostly A3 (both thick and thin in) with four short periods in the A1 state. After 00:59:24 UT, the attenuator state returned to A1 state.

To analyze count flux data in SPEX, a count rate spectrum file and a spectrometer response matrix (SRM) file must be read into the active session of SPEX. The response matrix is stored in the array DRM (for detector response matrix) within the SPEX common blocks. When using the RHESSI spectrum object or GUI to create the count rate spectrum file and response matrix file, the name of the response matrix file is written in the RESPFILE parameter in the header of the spectrum FITS file. A different srm file is needed to analyze the count rate data obtained in each attenuator state and detector combination. The srm file and count spectra files are written out from the Spectrum widget of the GUI as explained in "Spectroscopy -- First Steps". Alternatively, the srm files can be produced from the spectrum object (sp_ob->filewrite, /fits,/build, ... ). They are appropriate for the attenuator state in the first interval after the start time. If the attenuator state changes during the flare, then a new srm file must be generated for each state by choosing the first time interval with the new attenuator state.

The srm file is specified in SPEX with dfile, and then use read_drm to create the DRM array used with SPEX.

For this 23 July 2002 X4.8 event, one spectrum file and two srmfiles were saved with the GUI. They are:

If we want to analyze the spectra before 00:26:00 UT, we have to first read the spectrum file, and then read the srm file appropriate for the A1 state.

SPEX> _1file, hsi_spectrum_20020723_001000.fits
SPEX> preview
SPEX> graph
SPEX> dfile, hsi_srm_20020723_001000_atten1.fits
SPEX> read_drm
 

This should give the following response if everything is OK:

Command: read_drm
MRDFITS: Null image, NAXIS=0
MRDFITS: Binary table. 6 columns by 92 rows.
MRDFITS: Binary table. 3 columns by 1 rows.
minmax(drm) 0.000000 0.0738023
Change parameters or enter a command
 

If we want to analyze the spectra between 00:26:00 UT and 00:59:24 UT (for now, because of the pileup problem we will not try to analyze the time intervals during the four short periods in the A1 state), we have to read the srm file appropriate for the A3 state:

SPEX> dfile, hsi_srm_20020723_002600_atten3.fits
SPEX> read_drm
 

It will give a similar output as above. Again, for the analysis of spectra after 00:59:24 UT, we need to switch back to the A1 srm file:

SPEX> dfile,hsi_srm_20020723_001000_atten1.fits
SPEX> read_drm
 

Once the correct spectrum and srm files have been entered into SPEX, the analysis can proceed as described in Spectroscopy First Steps.

This page last updated: June 27, 2011