SOT quick analysis guide
This document contains some notes about using SOT data. The official SOT analysis guide is held at Lockheed.
SOT files can be downloaded from the Oslo SDC archive. On your
computer you should make sure that you have the environment variable
$HINODE_DATA defined, pointing to the top-level of your Hinode data
directory. For example:
setenv $HINODE_DATA = /user/home/data/hinode
If you choose the gzipped tar file option for the download,
then put the file in the $HINODE_DATA directory and unpack it. This
will ensure that your SOT data are correctly archived.
For SP data it's best to access the level-2 files from the Lockheed level-2 site.
Reading and prepping
The first thing to do is to query the SOT catalog for the
are interested in:
IDL> time0='16-feb-2011 06:30'
IDL> time1='16-feb-2011 09:30'
IDL> sot_cat, time0, time1, /level0, cat, files
The particular filters that are required can then be selected
which is a widget-based routine.
The subset of files is then selected and read with:
IDL> read_sot, cfiles, index, data
(Note that the Oslo archive gives the user gzipped files so
necessary to manually add the gzip file extension.)
The data can be directly prepped using:
IDL> fg_prep, cfiles, -1, index, data
Archiving the level-1 files
After running fg_prep you can store the level-1 files in your
data archive with:
IDL> for i=0,n-1 do
Note that sot_cat doesn't accept a /level1 keyword, so to read
the files you will have to follow the steps described above but use
str_replace again to swap 'level0' for 'level1'.
image frames returned by fg_prep should be co-aligned
relative to each other, and so extracting a sub-region from the 3D
array should yield a smooth movie sequence. I notice, however, that the
xcen,ycen values seem to have some jitter in them. So if you try to
interpolate the frames based on the xcen,ycen values then you'll
actually introduce jitter into the movie. It is best just to extract a
specific pixel range from the 3D data-cube to get a smooth movie.
However, the movie will only be steady for the feature being
tracked with the correlation tracker. If you're interested in another
feature in the field-of-view then you may find a systematic drift with
time (an active region with emerging flux is an example where this may
occur). There is no specific correction for this in the software at
When you use fg_prep, it seems it modifies the pointing
information from the coordinates that would be obtained by just doing
read_sot. This is consistent with Appendix C of the SOT analysis
The best SP data to get are the level-2 files, which have
2D maps of the various quantities. These can be downloaded from the Lockheed level-2 site by
cutting-and-pasting the appropriate line into Solarsoft. The level-2
files don't seem to be available at the Oslo site. The level-1
files consist of many individual FITS files for each exposure of the SP
scan. If you use sot_cat to search for SP scans, it will return a list
these individual FITS files.
The level-2 file can be read from Solarsoft with:
IDL> read_sotsp, l2file, index, data
Note that the type of each image is given by index.ftype.
There doesn't seem to be any special software for plotting the vector
- The SOT magnetograms have a reversed polarity compared to
Page maintained by Dr Peter R. Young