Description of Topra

(Demeter to Prassadco Convertor)

Topra is an IDL program for conversion of the wave data of the DEMETER satellite to the Prassadco format ("_sm" and "_aux" files). Its input are level-1 ELF data obtained during the burst mode, either by the ICE instrument ("1130" files), or the IMSC instrument ("1135" files) or both of them.

SOURCE CODE

INSTRUCTIONS

Topra calling sequence is:

Topra,'directory' [,fftlen=512] [,nave=3] [,/elonly]

"Directory" is the path to the directory containing the downloaded Demeter data files. All the files placed in this directory will be processed.

"FFTlen" is the number of data samples used in the Fast Fourier Transform. This parameter is optional, its default value is 256. Allowed FFT lengths are 32, 64, 128, 256, 512, 1024, 2048, 4096 (the upper limit is the size of the data block of the burst-mode ELF data).

"Nave" is the number of averaged spectral matrices. This parameter is optional, its default value is 3. Allowed values of this parameter are 1, 3, 7, 15, 31, 63, 127, 255).

The values of "FFTlen" and "Nave" must be chosen to have Fftlen * (Nave+1) <= 8192.

"/elonly" is an optional parameter defining that only the ICE electric field data will be used. By default both magnetic and electric data are used, and Topra processes the IMSC magnetic field data files in the given directory in the alphabetical order. The procedure always tries to find the corresponding ICE electric field data (replacing "1135" by "1130" in the file name). If the electric field data file does not exist, only the IMSC magnetic field data are used on the output. Note that, in this case, the number of available PRASSADCO data processing methods is reduced.

If the "elonly" switch is used, Topra ignores the magnetic field data and proceeds only with the electric field data files. Polarization of the electric field can be only investigated by PRASSADCO in this case.

RUNNING PRASSADCO

"Orbit information" can contain:

• "Fge" …electron gyro-frequency
• "MLT" …magnetic local time
• "Lat" …invariant latitude
• "Geocenlat" …geocentric latitude
• "Geocenlon" …geocentric longitude
• "Geomaglat" …geomagnetic latitude
• "Geomaglon" …geomagnetic longitude
• "Lpar" …Mc Ilwain parameter
• "Alt" …altitude (km)

"Data source" should be set to 0.
"Data type" values B1, B2, B3, E1, E2, E3 correspond to the components of magnetic and electric field. Note that if the "elonly" switch is used, "Data type" values B1, B2, B3 correspond to the components of the electric field.