This page (revision-1) was last changed on 07-Dec-2016 14:14 by Peter Young

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AIARespike
AIARespike

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!!!Re-spiking AIA images
This page explains how to re-spike AIA images, and gives information about the AIA spikes files. AIA images are automatically de-spiked when converted from level-0 to level-1, ''however'' only the EUV wavelengths are de-spiked. The FUV wavelengths (1600, 1700) are not de-spiked.
Examples of solar features that can be affected by spike removal are flare kernels ([Young et al. 2013|http://adsabs.harvard.edu/abs/2013ApJ...766..127Y]) and jets ([Young & Muglach 2014|http://adsabs.harvard.edu/abs/2014SoPh..289.3313Y]), but essentially any small-scale, intense solar feature can be affected
!!The aia_respike routine
This is run as follows:
{{{
IDL> read_sdo, aia_file, index, data, /use_shared_lib
IDL> aia_respike, index, data, outindex, outdata
}}}
The routine automatically downloads the spikes file from the JSOC and puts it in your working directory (look for spikes.fits). All spikes in {{data}} are re-filled with their original values. __Make sure that you run aia_respike before you run aia_prep!__ (aia_prep will re-scale the images so the image is re-sampled and the spikes no longer correspond to their original positions.)
aia_respike also works on cutout data, but __the cutout file must be in standard level-1 format__. In particular, if you download the cutouts from the JSOC you should not use the register option, nor should you scale the images. Also, you should run aia_respike before you run aia_prep.
!!The spikes files
Since aia_respike automatically downloads the spikes files, then generally you will not need to download them yourself. However, to get them from JSOC you have to use the RecordSet:
{{{
aia.lev1_euv_12s[2011.02.10_05:00/40m@1m][193]{spikes}
}}}
i.e., you append {spikes} to the query. There is no equivalent of cutouts for the spikes files - you have to download the whole file. For a single EUV wavelength, a complete day's worth of spikes files (7200 in all) will take up about 1 Gbyte of space.
The spikes file is read with read_sdo:
{{{
IDL> read_sdo, spike_file, index, data, /use_shared_lib
}}}
and you will see that {{data}} has a size (N,3) where N is the number of spikes. The first element gives the location of the spike as an integer. This can be converted to a 2D location using the SSW routine get_ij:
{{{
IDL> ij=get_ij(data[0,0],4096)
}}}
where 4096 is input because this is the size of full-disk AIA images.
The 2nd element of the array ({{{data[*,1]}}}) is the original value at the spike location, and the 3rd element ({{{data[*,2]}}}) is the value after the spike has been replaced.
!!Batch processing
If you want to re-spike a whole sequence of AIA images, then it's probably best to download the spikes files in advance, and then give the spikes data as an input to aia_respike (I've had problems whereby aia_respike fails to connect to JSOC to retrieve the spikes file and then it crashes). This can be done as follows:
{{{
IDL> read_sdo, aia_file, index, data, /use_shared_lib
IDL> read_sdo, spike_file, spk_index, spk_data, /use_shared_lib
IDL> aia_respike, index, data, outindex, outdata, ispikedd=spk_data
}}}
Of course make sure that your spikes file matches the data file to which it applies.
This page (revision-1) was last changed on 07-Dec-2016 14:14 by Peter YoungTop