EUVI analysis guide


This guide gives some basic information for getting started with EUVI data. For more detailed information, check the SECCHI data user guide. There is also useful information in the COR1 User Guide that is applicable to EUVI.

Downloading and ingesting data

Firstly create a directory where you plan to store the EUVI data, and then add the following line to your IDL startup file:

setenv,'SECCHI_LZ=/data/stereo'

where /data/stereo is the directory where you'll be keeping the data.

Data can be obtained from the NRL database page (this doesn't seem to work anymore - see VSO section below). After retrieving the tar file, put it in a temporary directory and unpack it:

> cd euvi_temp
> tar xvf file.tar

Then go into IDL and do:

IDL> sccingest,'.'

this takes the files from the tar file and places them into your /data/stereo directory making sure they match the official SECCHI directory structure.

The COR1 User Guide explains the filename format. In particular, there is a five-letter code in the filename such as "n4euA". The first letter will always be 'n' (normal) for EUVI, the second character will usually be 4 for a synoptic image, 5 for a special sequence (e.g., a CME is detected so extra images are obtained), or 7 for a low-resolution beacon image. The 3rd and 4th characters are 'eu' for EUVI, and the 5th character gives the spacecraft (A or B).

Getting data from the VSO

The following shows how images can be obtained from the VSO for a specific wavelength and satellite:

IDL> list=vso_search('17-jul-2014 07:00','17-jul-2014 11:00',inst='euvi',wave=304,source='stereo_a')
IDL> a=vso_get(list)

Extracting images from one filter

If you've downloaded a full set of images for a single day you may want to pick out only images from 195, say. The best way to do this is with the widget routine scc_lister:

IDL> list_struct=scc_lister()

Once you've selected your image set, then read them with secchi_prep:

IDL> secchi_prep, list_struct.sc_a, hdr, im, rotate=1, /smask, /interp

(For the case where the files correspond to spacecraft A.) If you want to shrink the images down to 1024 pixels, then set outsize=1024.

If you prefer to filter the image set on the command line, then try, e.g.,

IDL> list_struct=scclister('20090113..20090114', 'EUVI',  sc='b', size='2048', filt='S1',dest='SSR1', polar=171, sort_type='ascending',sort_by='DateObs')

Note that the keyword 'polar' is used to select wavelength, and dest takes 'SSR1' for synoptic images and 'SSR2' for special event sequences (e.g., CMEs).

Spacecraft separation angle

To determine the separation angle between the either of the STEREO spacecraft and Earth, do, e.g.,

IDL> angle=get_stereo_sep_angle('2009-11-22 02:14','B','Earth',/degrees)


Page maintained by Dr Peter R Young.