Creating IDL maps from EIS data#

IDL maps are a widely used means of storing and using solar image data, and are very useful for comparing data-sets from different instruments. The sections below describe different ways of creating maps from EIS data. Please check Dominic Zarro's IDL map webpage for more details on how to use maps. A basic operation is to plot a map:

IDL> plot_map, map

Note that velocity and line width maps can be created from EIS data in addition to intensity maps.

Quick method#

An intensity map can be quickly generated from the EIS data object (DATA) using, e.g.,

IDL> mmap=data->mk_eis_map(195.12)

which simply sums all wavelength pixels in the data window containing the wavelength 195.12 line. This map should not be used for detailed science analysis, but is useful for taking a quick look at the data. Warning: if there is more than one emission line in the data window, then the map may not look as expected.

Creating a map using moments#

Moments are usually used as a quick means of estimating the intensity, velocity and width of an emission line without having to do Gaussian fits. They are obtained by doing, e.g.,

IDL> m=obj_new(‘eis_moment’,data,iwin=195.12)

A widget will pop up allowing you to define the emission line and continuum to be used for the moments.

A list of methods for 'm' can be obtained by doing:

IDL> m->help

With the moment object created, maps containing intensity, velocity and line width are created using:

IDL> intmap=m->mk_eis_map(195.12)
IDL> velmap=m->mk_eis_map(195.12,/vel)
IDL> widmap=m->mk_eis_map(195.12,/wid)

Creating a map from Gaussian fits#

These are done in the same way as the moments by adding the keyword /gauss:

IDL> m=obj_new(‘eis_moment’,data,iwin=195.12,/gauss)

You will again be asked to define the line and continuum for the fit.

The maps are created with:

IDL> intmap=m->mk_eis_map(195.12)
IDL> velmap=m->mk_eis_map(195.12,/vel)
IDL> widmap=m->mk_eis_map(195.12,/wid)

Creating a map from the eis_auto_fit output#

The Gaussian fitting routine EIS_AUTO_FIT is described in EIS Software Note No. 16, and it returns a structure containing the fit results. Maps can be created from this structure using the routine EIS_GET_FITDATA and specifying the /MAP keyword:

IDL> intmap=eis_get_fitdata(fitdata,/int,/map)
IDL> velmap=eis_get_fitdata(fitdata,/vel,/map)
IDL> widmap=eis_get_fitdata(fitdata,/wid,/map)

Technical details for generating a map#

An IDL map is generated through the command:

map=make_map(array,xc=xc,yc=yc,dx=dx,dy=dy,time=time)

where xc and yc give the X and Y coordinates of the image center, dx and dy give the size of the pixels in arcsecs, and time is the time of the observation.

This information can be obtained from the windata structure (produced by EIS_GETWINDATA):

xc=windata.xcen
yc=windata.ycen
dx=windata.scale[0]
dy=windata.scale[1]
time=windata.date_obs